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Diagnostic Aids

NOTE: After each service or repair procedure has been completed, reconnect all components. Clear DTCs and repeat QUICK TEST  procedures to ensure all EEC-V systems are working properly and DTCs are no longer present.

Perform this test when instructed during QUICK TEST or if directed by other test procedures. Only use this test to diagnose the following.

NOTE: HO2S may be displayed on scan tool as 02S.

To prevent replacement of good components, be aware the following non-EEC areas may be cause of driveability concerns:

NOTE: Proceed to DTC testing steps listed in FAULT CODE SETTING CONDITION  table of fault code setting condition.
FAULT CODE SETTING CONDITION

Fault Code KOEO KOER Continuous Memory
P0131      H27
P0133      H20
P0135 1   H30  H30  H30
P0136      H80
P0141 1   H30  H30  H30
P0151      H27
P0153      H20
P0155 1   H30  H30  H30
P0156      H80
P0161 1   H30  H30  H30
P0171 1       H41
P0172 1       H41
P0174 1       H41
P0175 1       H41
P0201  H56  H56  H56
P0202  H56  H56  H56
P0203  H56  H56  H56
P0204  H56  H56  H56
P0205  H56  H56  H56
P0206  H56  H56  H56
P0207  H56  H56  H56
P0208  H56  H56  H56
P0209  H56  H56  H56
P0210  H56  H56  H56
P0211  H56  H56  H56
P0212  H56  H56  H56
P1127 1     H100  
P1128 1     H110  
P1129 1     H110  
P1130 1       
P1131 1     H40  H40
P1132 1     H40  H40
P1137    H80  
P1138    H80  
P1150 1       H40
P1151 1   H40  H40  H40
P1152 1     H40  H40
P1157    H80  
P1158    H80  
(1) For Natural Gas Engines see
FAULT CODE SETTING CONDITION 
NOTE: Test procedure begins with step 20). No test procedures have been omitted.

  1. 20) Perform KOER Self-Test

    Perform KOER on-demand self-test. See KOER ON-DEMAND SELF-TEST  under QUICK TEST. If DTC P1127, P1128 or P1129 is present, go to appropriate system test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If DTC P1127, P1128 or P1129 is not present, go to next step.

  2. 21) DTC P0133 & P0153: HO2S Response Test

    This DTC indicates that response rate is below calibration in HO2S as follows:

    Possible causes are:

    • Open Or Shorted Circuit
    • Exhaust Leak
    • Excessive Fueling
    • HO2S Coated With Contaminants
    • Faulty MAF Sensor
    • Leak In Air Induction System

    Turn ignition switch to ON position. Using scan tool, access GENERIC OBD-II FUNCTIONS and enter. Select DIAGNOSTIC MONITORING TEST RESULTS and enter. Scroll to TEST ID: 01 and enter. Press START. If measured value is less than minimum threshold, go to next step. If measured value greater than minimum threshold, fault cannot be identified at this time. Perform HO2S MONITOR REPAIR VERIFICATION DRIVE CYCLE. See FUEL MONITOR OR HO2S MONITOR REPAIR VERIFICATION DRIVE CYCLE under DRIVE CYCLE PROCEDURES  under ADDITIONAL SYSTEM FUNCTIONS. Repeat step  20). If DTC P1127, P1128 or P1129 is not present, testing is complete.

    Fig 1: Locating HO2S (4-Cylinder)
    G95I35970Courtesy of FORD MOTOR CO.
    Fig 2: Locating HO2S (V6 Or V8 With Dual Exhaust)
    G95A35972Courtesy of FORD MOTOR CO.
    Fig 3: Locating HO2S (V6 Or V8 With Single Exhaust)
    G95B35973Courtesy of FORD MOTOR CO.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 21) to step 23). No test procedures have been omitted.

  3. 23) Check For Unmetered Air Leaks

    Vacuum or air leaks in non-EEC-V areas could cause fault code to set. Check the following as potential source of air leak:
    • Leaking Vacuum Hoses
    • Leaking Intake Manifold Gasket
    • Exhaust Leaks At Flanges Or Gaskets
    • PCV System
    • Poorly Seated Oil Dip Stick &/Or Dipstick Tube Or Cap

    If none of these conditions are present, go to next step. If any of these conditions are present, repair source of air leak as necessary. Perform HO2S MONITOR REPAIR VERIFICATION DRIVE CYCLE. See FUEL MONITOR OR HO2S MONITOR REPAIR VERIFICATION DRIVE CYCLE under DRIVE CYCLE PROCEDURES  under ADDITIONAL SYSTEM FUNCTIONS.

  4. 24) Check HO2S Circuits

    Turn ignition switch to OFF position. Disconnect suspect HO2S harness connector. Connect a jumper wire between HO2S SIG and VPWR terminals at suspect HO2S harness connector. See Fig 4 or Fig 5 . Turn ignition switch to ON position. Using scan tool, select appropriate HO2S PID from PID/DATA MONITOR & RECORD menu. If PID voltage is 1.5 volts or less, remove jumper wire and go to next step. If PID voltage is more than 1.5 volts, replace HO2S and change engine oil and filter. Perform HO2S MONITOR REPAIR VERIFICATION DRIVE CYCLE. See FUEL MONITOR OR HO2S MONITOR REPAIR VERIFICATION DRIVE CYCLE under DRIVE CYCLE PROCEDURES  under ADDITIONAL SYSTEM FUNCTIONS.
    Fig 4: Identifying HO2S Connector Terminals (Contour, Cougar & Mystique)
    G95C35966Courtesy of FORD MOTOR CO.
    Fig 5: Identifying HO2S Connector Terminals (Except Contour, Cougar & Mystique)
    G95E35968Courtesy of FORD MOTOR CO.

  5. 25) Check HO2S Signal Circuit Resistance

    Turn ignition switch to OFF position. Disconnect PCM connector(s). Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Measure resistance of HO2S SIG circuit between suspect HO2S PCM connector terminal and HO2S SIG terminal at HO2S harness connector. See HO2S PCM TERMINAL IDENTIFICATION (CONTOUR, COUGAR & MYSTIQUE) , HO2S PCM TERMINAL IDENTIFICATION (LS)  or HO2S PCM TERMINAL IDENTIFICATION (EXCEPT CONTOUR, COUGAR, LS & MYSTIQUE)  table. Measure resistance between PCM connector terminal No. 91 and SIG RTN terminal at suspect HO2S harness connector. If both resistance readings are less than 5 ohms, go to next step. If any resistance reading is 5 ohms or more, repair open circuit. Perform HO2S MONITOR REPAIR VERIFICATION DRIVE CYCLE. See FUEL MONITOR OR HO2S MONITOR REPAIR VERIFICATION DRIVE CYCLE under DRIVE CYCLE PROCEDURES  under ADDITIONAL SYSTEM FUNCTIONS.
    HO2S PCM TERMINAL IDENTIFICATION (CONTOUR, COUGAR & MYSTIQUE) (1)

    Application HO2S SIG PCM Terminal No. HO2S HTR PCM Terminal No.
    HO2S-11 60 (2) 73
    HO2S-12 35 100
    HO2S-21 87 99
    HO2S-22 61 101
    (1) SIG RTN circuit is PCM terminal No. 91. VPWR circuit is PCM terminal No. 71 and 97.
    (2) Cougar 2.0L is terminal No. 93.
    HO2S PCM TERMINAL IDENTIFICATION (LS) (1)

    Application HO2S SIG PCM Terminal No. HO2S HTR PCM Terminal No.
    HO2S-11 C45 B7
    HO2S-12 C28 C15
    HO2S-21 C44 B8
    HO2S-22 C29 C16
    (1) SIG RTN circuit is PCM terminal No. B7 and C17. VPWR circuit is PCM terminal No. A32 and A33.
    HO2S PCM TERMINAL IDENTIFICATION (EXCEPT CONTOUR, COUGAR, LS & MYSTIQUE) (1)

    Application HO2S SIG PCM Terminal No. HO2S HTR PCM Terminal No.
    HO2S-11 60 93
    HO2S-12 35 95
    HO2S-21 87 94
    HO2S-22 61 96
    (1) SIG RTN circuit is PCM terminal No. 91. VPWR circuit is PCM terminal No. 71 and 97.

  6. 26) Check HO2S SIG Circuit For Short To VPWR

    Disconnect scan tool from Data Link Connector (DLC). Measure resistance between PCM harness connector VPWR and HO2S SIG terminals. Refer to appropriate HO2S PCM TERMINAL IDENTIFICATION table. If all resistance readings are more than 10 k/ohms, go to next step. If any resistance reading is 10 k/ohms or less, go to step  28).

  7. 27) Check For Source Of Potential HO2S Contamination

    Check the following areas for cause of contamination:
    • Use Of Unapproved Silicone Sealers
    • Fuel Contaminated By Silicone Fuel Additives
    • Excessive Oil Burning
    • Antifreeze Leaking Internally In Engine
    • Lead Contaminated Fuel
    • Short Trip Driving In Cold Weather
    • Use Of Unapproved Cleaning Products

    If any conditions exist, repair source of contamination and replace HO2S, oil and filter. Perform HO2S MONITOR REPAIR VERIFICATION DRIVE CYCLE. See FUEL MONITOR OR HO2S MONITOR REPAIR VERIFICATION DRIVE CYCLE under DRIVE CYCLE PROCEDURES  under ADDITIONAL SYSTEM FUNCTIONS. If none of the conditions exist, replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Program PCM. See FLASH VEHICLE IDENTIFICATION BLOCK PROCEDURE .

  8. 28) Verify Wiring Is In Proper Terminal Location

    Ensure ignition switch is in OFF position. Disconnect suspect HO2S. Disconnect PCM connector(s). Inspect connectors for loose, damaged or corroded terminals. Repair as necessary. Measure resistance between PCM connector terminal and HO2S SIG terminal at suspect HO2S harness connector. Measure resistance between PCM connector terminal and SIG RTN terminal at suspect HO2S harness connector. See HO2S PCM TERMINAL IDENTIFICATION (CONTOUR, COUGAR & MYSTIQUE) , HO2S PCM TERMINAL IDENTIFICATION (LS)  or HO2S PCM TERMINAL IDENTIFICATION (EXCEPT CONTOUR, COUGAR, LS & MYSTIQUE)  . If both resistance readings are less than 5 ohms, replace HO2S. If any resistance reading is 5 ohms or more, repair wiring as necessary.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 28) to step 30). No test procedures have been omitted.

  9. 30) DTC P0135, P0141, P0155 Or P0161: HO2S Heater Circuit

    DTCs received separately indicate a short to ground or open circuit in HO2S heater circuit. DTCs received in pairs, such as P0135 and P0155 or P0141 and P0161, indicate HO2S heater circuit is shorted to a power source of more than 2 volts. HO2S DTC identification is as follows:
    • DTC P0141 Is For HO2S-12
    • DTC P0155 Is For HO2S-21
    • DTC P0161 Is For HO2S-22

    Refer to illustrations for HO2S identification. See Fig 1-Fig 3 . Possible causes are:

    • Signal Shorted In Wiring Harness Or HO2S
    • Water In Connectors
    • Cut Or Pulled Wires
    • Open In GND Or VPWR Circuit
    • Corroded Terminals
    • Faulty HO2S Heater

    Inspect HO2S connectors for loose, damaged or corroded terminals. Repair as necessary. If HO2S connectors are okay, go to next step.

  10. 31) Perform KOEO Self-Test

    Start engine and operate at 2000 RPM for one minute. Turn ignition switch to OFF position. Perform KOEO ON-DEMAND SELF-TEST . If DTC P0135, P0141, P0155 or P0161 is present, go to next step. If specified DTCs are not present, fault is intermittent. Go to TEST Z .

  11. 32) Check For VPWR Voltage At HO2S Heater Wiring Harness Connector

    Turn ignition switch to OFF position. Disconnect suspect HO2S. Inspect wiring harness for damage and repair as necessary. Turn ignition switch to ON position. Measure voltage between SIG RTN and VPWR terminals at suspect HO2S harness connector. If voltage is more than 10.5 volts, go to next step. On LS, if voltage is 10.5 volts or less, go to TEST B, step  5). On all other models, if voltage is 10.5 volts or less, check circuit fuse. Replace as necessary. If fuse is okay, repair open circuit.

  12. 33) Check For Short Circuit

    Disconnect scan tool from DLC. Disconnect PCM connector(s). Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Measure resistance between PCM harness connector suspect HO2S HTR circuit terminal and PWR GND terminal. Also, measure resistance between HO2S HTR terminal and SIG RTN and VPWR terminals at suspect HO2S harness connector. See Fig 4 or Fig 5 . If both resistance readings are more than 10 k/ohms, go to next step. If any resistance reading is 10 k/ohms or less, repair short circuit.

  13. 34) Check For Open Circuit

    Leave ignition switch in OFF position and HO2S disconnected. Measure resistance between HO2S HTR terminal at suspect HO2S harness connector and appropriate HO2S HTR terminal at PCM connector. See HO2S PCM TERMINAL IDENTIFICATION (CONTOUR, COUGAR & MYSTIQUE)  or HO2S PCM TERMINAL IDENTIFICATION (EXCEPT CONTOUR, COUGAR & MYSTIQUE)  table. If resistance is 4 ohms or more, repair heater circuit for open or excessive resistance in wiring harness. If resistance is less than 4 ohms, go to next step.

  14. 35) Check HO2S Heater Resistance

    Turn ignition switch to OFF position. With suspect sensor disconnected, measure resistance between HO2S HTR terminal and VPWR terminal at suspect HO2S. If resistance is 3-30 ohms, go to next step. If resistance is not 3-30 ohms, replace HO2S.

  15. 36) Check HO2S Case For Short To VPWR, HTR Or SIG RTN

    Measure resistance between HO2S component case and HO2S connector HO2S HTR, SIG RTN and VPWR terminals. If all resistance measurements are more than 10 k/ohms, replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Program PCM. See FLASH VEHICLE IDENTIFICATION BLOCK PROCEDURE . If any resistance measurement is 10 k/ohms or less, replace HO2S.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 36) to step 40). No test procedures have been omitted.

  16. 40) DTCs P1130, P1150, P1131, P1151, P1132 Or P1152: Upstream HO2S Or Fuel System Not Switching

    DTCs P1131 and P1151 indicate air/fuel ratio is correcting rich for an overly lean condition. DTCs P1132 and P1152 indicate air/fuel ratio is correcting lean for an overly rich condition. DTCs P1130 and P1150 indicate when an HO2S fails to switch due to a circuit or fuel exceeding a calibrated limit. Possible causes are:

    • Fuel System

      Excessive fuel pressure, leaking or contaminated fuel injectors, leaking fuel pressure regulator, low fuel pressure or engine running out of fuel or vapory recovery system fault.

    • Induction System

      Air leaks after MAF sensor, air intake system obstructions, vacuum leaks, PCV system or improperly seated engine oil dipstick.

    • EGR System

      Leaking gasket, stuck EGR valve or leaking diaphragm or EVR.

    • Engine Mechanical

      Engine oil overfilled, cam timing, cylinder compression or exhaust leaks before or near HO2S.

    Inspect engine for obvious defects in specified systems. Repair as necessary. If no faults are found, go to TEST DC, step  25).

  17. 41) Continuous Memory DTC P0171, P0172, P0174 Or P0175: Fuel System At Corrected Fuel Trim

    DTCs P0171, P0172, P0174 and P0175 indicate a problem when adaptive fuel strategy senses a lean or rich condition beyond the minimum or maximum calibrated limit. Possible causes for these faults are.

    • Fuel System

      Excessive fuel pressure, leaking or contaminated fuel injectors, leaking fuel pressure regulator, low fuel pressure or engine running out of fuel or vapory recovery system fault.

    • Induction System

      Air leaks after MAF sensor, air intake system obstructions, vacuum leaks, PCV system or improperly seated engine oil dipstick.

    • EGR System

      Leaking gasket, stuck EGR valve or leaking diaphragm or EVR.

    • Engine Mechanical

      Engine oil overfilled, cam timing, cylinder compression or exhaust leaks before or near HO2S.

    Inspect engine for obvious defects in specified systems. Repair as necessary. If no faults are found, go to TEST DC, step  25).

  18. 42) Perform KOER Self-Test

    Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). Disconnect fuel vapor hose from intake manifold and plug fitting at intake manifold. Start engine, and operate at 2000 RPM for 5 minutes, then allow to return to idle. Perform KOER ON-DEMAND SELF-TEST  and proceed as follows:
    • If DTCs P1127, P1128 or P1129 are present, go to appropriate system test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
    • If DTC (P1130, P1131) or (P1150, P1151) is present, go to next step.
    • If DTC (P1130, P1132) or (P1150, P1152) is present, go to step  49).

    If none of these DTCs are present, proceed as follows:

    • If Continuous Memory DTC P1130, P1150, P0171, P0172, P0174 or P0175 is present, go to step  52).
    • If DTCs P1132 and/or P1152 is no longer present, reconnect fuel vapor line.
    • If KOER DTCs P1131, P1132, P1151 and/or P1152 are present, perform evaporative system leakage tests. See EVAPORATIVE EMISSIONS DIAGNOSTIC TROUBLE CODE DEFINITIONS  under SYSTEM TESTS (EVAPORATIVE EMISSIONS).
    • On all others without reoccurring DTCs, fault is unable to be duplicated at this time. Go to TEST Z .

  19. 43) HO2S Circuit Test (With Lean DTCs)

    Disconnect suspect HO2S. Turn ignition switch to ON position. Using scan tool, select appropriate HO2S PID from PID/DATA MONITOR & RECORD menu. Connect a jumper wire between HO2S SIG and VPWR terminals at suspect HO2S harness connector. If spark occurs, remove jumper wire and go to step  47). If HO2S voltage is more than 1.3 volts, go to next step. If voltage is 1.3 volts or less, go to step  46).

  20. 44) Check Circuit Resistance

    Turn ignition switch to OFF position. Reconnect PCM connector. Measure resistance between negative battery terminal and SIG RTN terminal at suspect HO2S harness connector. If resistance is less than 5 ohms, go to step  52). If resistance is 5 ohms or more, go to next step.

  21. 45) Check For Open Circuit

    Turn ignition switch to OFF position. Disconnect PCM connector(s). Measure resistance between PCM connector terminal No. 91 (SIG RTN) and SIG RTN terminal at suspect HO2S harness connector. If resistance is less than 5 ohms, replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Program PCM. See FLASH VEHICLE IDENTIFICATION BLOCK PROCEDURE . If resistance is 5 ohms or more, repair open circuit.

  22. 46) Check HO2S SIG Circuit For Open

    Turn ignition switch to OFF position. Disconnect PCM connector(s). Disconnect suspect HO2S connector. Inspect connectors for loose, damaged or corroded terminals. Repair as necessary. Measure resistance of HO2S SIG circuit between HO2S SIG terminal at suspect HO2S harness connector and appropriate HO2S SIG terminal at PCM connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit.

  23. 47) Check HO2S Circuit For Short To Ground

    On LS, measure resistance between PCM connector terminals No. B7, C17 (SIG RTN), A24, A25, A26 and A27 (PWR GND) and appropriate HO2S SIG terminal at PCM connector. On all other models, measure resistance between PCM connector terminals No. 91 (SIG RTN) and 103 (PWR GND) and appropriate HO2S SIG terminal at PCM connector. If all resistance readings are more than 10 k/ohms, go to next step. If any resistance reading is 10 k/ohms or less, repair short circuit.

  24. 48) Check HO2S For Short To Ground

    Reconnect suspect HO2S connector. On LS, measure resistance between PCM connector terminals No. B7, C17 (SIG RTN), A24, A25, A26 and A27 (PWR GND) and suspect HO2S SIG terminal at PCM connector. On all other models, measure resistance between PCM connector terminals No. 91 (SIG RTN) and 103 (PWR GND) and suspect HO2S SIG terminal at PCM connector. If any resistance reading is 10 k/ohms or less, replace HO2S. If both resistance readings are more than 10 k/ohms, replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Program PCM. See FLASH VEHICLE IDENTIFICATION BLOCK PROCEDURE .

  25. 49) Check HO2S Circuit (Rich DTCs)

    Ensure ignition switch is turned to OFF position. Disconnect suspect HO2S harness connector. Turn ignition switch to ON position. Using scan tool, select appropriate HO2S PID from PID/DATA MONITOR & RECORD menu. If HO2S PID voltage is more than .2 volt, go to next step. If HO2S PID voltage is .2 volt or less, go to step  51).

  26. 50) Check For Short To Power

    Turn ignition switch to OFF position. Disconnect scan tool from DLC. Disconnect PCM connector(s). Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Using a DVOM, measure resistance between PCM harness connector suspect HO2S SIG and VPWR terminals, and HO2S SIG and HO2S HTR terminals. See HO2S PCM TERMINAL IDENTIFICATION (CONTOUR, COUGAR & MYSTIQUE)  or HO2S PCM TERMINAL IDENTIFICATION (EXCEPT CONTOUR, COUGAR & MYSTIQUE)  table. If both resistance measurements are more than 10 k/ohms, replace PCM. See FLASH VEHICLE IDENTIFICATION BLOCK PROCEDURE . If either resistance measurement is 10 k/ohms or less, repair short to HO2S HTR or VPWR circuit.

  27. 51) Check HO2S SIG For Short To HO2S HTR Circuit In Sensor

    With suspect HO2S harness connector disconnected. Using a DVOM, measure resistance between suspect HO2S connector HO2S SIG and HO2S HTR terminals. See Fig 4 or Fig 5 . If resistance measurement is more than 10 k/ohms, go to next step. If resistance measurement is 10 k/ohms or less, replace HO2S.
    28. NOTE: Fuel pump will only operate for 8 seconds when OUTPUT TEST MODE is activated.

  28. 52) Check Fuel Pressure
    Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). Release fuel system pressure. See FUEL SYSTEM PRESSURE RELEASE procedure under FUEL SYSTEM in appropriate REMOVAL, OVERHAUL & INSTALLATION article. Install fuel pressure gauge. Using scan tool, access OUTPUT TEST MODE  under ADDITIONAL SYSTEM FUNCTIONS. Command fuel pump ON. Record fuel pressure. See FUEL PRESSURE SPECIFICATIONS . If fuel system pressure is not as specified, go to TEST HC . If fuel system pressure is as specified, go to next step for vehicles with returnable fuel system, or go to step  55) for vehicles with returnless fuel system. See FUEL SYSTEM IDENTIFICATION  table.
    FUEL SYSTEM IDENTIFICATION

    Application Fuel System
    Continental, Contour, Cougar, Escort, Focus, Mystique, Sable & Taurus Electronic Returnless
    Explorer, Mountaineer & Ranger Mechanical Returnless
    All Others (1) Returnable
    (1) Fuel is returned to fuel tank by means of return line from fuel rail.

  29. 53) Check Fuel System For Pressure Stability

    With fuel pressure gauge installed, cycle ignition from OFF to ON position 3-4 times to pressurize fuel system (DO NOT start engine). If fuel pressure does not remain within 5 psi (34 kPa) of maximum pressure after one minute, go to TEST HC, step  5). If fuel pressure remains within 5 psi (34 kPa) of maximum pressure reading for one minute, proceed as follows:
    • For DTCs P1130, P1150, P0171, P0172, P0174 and P0175, go to next step.
    • For HO2S DTCs displayed with misfire DTCs, go to step  56).
    • For all other DTCs, go to step  59).

  30. 54) Check Fuel System For Pressure Stability With Ignition ON

    With fuel pressure gauge installed, cycle ignition from OFF to ON position 3-4 times to pressurize fuel system (DO NOT start engine). Note fuel pressure with ignition switch turned to ON position. If fuel pressure remains within 5 psi (34 kPa) of maximum pressure after 10 seconds, go to next step. If fuel pressure drops more than 5 psi (34 kPa) of maximum pressure after 10 seconds, go to next step.

  31. 55) Check Injector Fault PIDs & Associated DTCs

    Turn ignition switch to ON position. Using scan tool, select INJ1F-INJ10F PIDs from PID/DATA MONITOR & RECORD menu. If misfire DTCs are present, select only injector fault PIDs that correspond to misfire DTCs. If DTCs P0201-P0212 or PID value indicates a injector fault, go to next step. If DTCs P0201-P0212 are not present, PID values do not indicate injector fault and any DTCs P0300-P0310 are present, go to TEST HD, step  12). If DTCs P0201-P0212 are not present, PID values do not indicate injector fault and any other DTC is present, go to step  59).
    32. NOTE: Performing this test step will erase Continuous Memory DTCs.
    NOTE: If misfire DTCs are present with fuel control DTCs, use misfire DTCs to determine which fuel injector circuits require testing.

  32. 56) Check Fuel Injector & Circuit Resistance
    Turn ignition switch to OFF position. Disconnect PCM connector(s). Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Using a DVOM, measure and record resistance between PCM harness connector VPWR and suspect fuel injector circuit terminals. See FUEL INJECTOR PCM TERMINAL IDENTIFICATION  table. Use injector fault PID noted in step  55) to determine fuel injector circuits that require testing. Resistance should be 11-18 ohms. If resistance is not as specified, go to next step. If resistance is as specified, replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Program PCM. See FLASH VEHICLE IDENTIFICATION BLOCK PROCEDURE .
    FUEL INJECTOR PCM TERMINAL IDENTIFICATION

    Injector No. PCM Terminal No.
    Contour, Cougar & Mystique 2.5L
    1 70
    2 96
    3 20
    4 95
    5 93
    6 94
    LS
    1 C2
    2 C14
    3 C24
    4 C32
    5 C11
    6 C21
    7 (1) C29
    8 (1) C37
    All Other Models
    1 75
    2 101
    3 74
    4 100
    5 (1) 73
    6 (1) 99
    7 (1) 72
    8 (1) 98
    9 (1) 68
    10 (1) 42
    (1) If applicable.

  33. 57) Check Resistance Of Fuel Injector Circuit

    Turn ignition switch to OFF position. Disconnect suspect fuel injector connector. Measure resistance between PCM connector terminals A32 and A33 (VPWR) on LS, or terminals No. 71 and 97 (VPWR) and VPWR terminal at suspect fuel injector harness connector. See Fig 6. Measure resistance between fuel injector signal circuit terminal(s) at PCM connector and same fuel injector circuit terminal at suspect fuel injector harness connector. If all resistance readings are less than 5 ohms, go to next step. If any resistance reading is 5 ohms or more, repair open circuit.
    Fig 6: Identifying Fuel Injector Connector Terminals
    G99D02109Courtesy of FORD MOTOR CO.

  34. 58) Check Fuel Injector Circuit For Short To Power Or Ground

    On LS, measure resistance between PCM connector fuel injector signal terminal(s) and terminals No. A32 and A33 and A24, A25, A26 and A27. On all other models, measure resistance between PCM connector fuel injector signal terminal(s) and terminals No. 71 and 97 and 103. Measure resistance between PCM connector fuel injector signal terminal(s) and ground. If all resistance readings are more than 10 k/ohms, go to next step. If any resistance reading is less than 10 k/ohms, repair short circuit.

  35. 59) Check Fuel Injector Flow & Leakage

    Turn ignition switch to OFF position. Reconnect PCM and fuel injector connector(s). Use Rotunda fuel injector tester from Fuel Tester Kit (113-00114) to flow test fuel injectors. Follow injector tester instructions. If fuel injector flow or leakage rate is not okay, replace defective fuel injector(s). If flow rate for each fuel injector is okay, proceed as follows:
    • For DTCs P1131 and P1151, go to next step.
    • For DTCs P0171, P0174, P1130, and P1150, go to step  61).
    • For DTCs P1132 and P1152, go to step  64).
    • For DTCs P0172 and P0175, fault is intermittent. Go to TEST Z .

  36. 60) Check For Secondary Air Intrusion

    If vehicle is not equipped with secondary air injection, go to next step. Possible causes for an HO2S always lean condition are:
    • Leak In Secondary Air Injection Pump Hoses
    • Secondary Air Diverted Upstream Of HO2S

    Turn ignition switch to OFF position. Disconnect secondary air injection hoses from engine and plug air injection ports (engine side). With engine at operating temperature, perform KOER ON-DEMAND SELF-TEST  under QUICK TEST. If DTC P1131 or P1151 is present, reconnect air injection hoses and go to next step. If DTCs P1131 or P1151 are not present, check secondary air injection system. See TEST HM, step  7).

  37. 61) Check Air Induction System For Air Leaks

    Check air induction system for leaks. Check PCV system for leaks. Check vacuum hoses for damage and tight connections. Check intake manifold gaskets. If any faults are found, repair as necessary. If no faults are found, proceed as follows:
    • For Continuous Memory DTCs P0171, P0174, P1130 or P1150, fault is intermittent. Go to TEST Z .
    • For DTCs P1131 and P1130, or P1151 and P1150, go to next step.

  38. 62) Check Cylinder Compression

    Using compression gauge, check cylinder compression. If cylinder compression is not okay, repair engine as necessary. If compression is okay, go to next step (DTCs P1130, P1131, P1150 and P1151) or step  64) (DTCs P1132 and P1152). If misfire DTCs are displayed with fuel control DTCs, go to TEST HD, step  20).

  39. 63) Check HO2S Ability To Generate Voltage More Than .5 Volt

    Any vacuum or air leaks can cause DTCs P1130, P1131, P1150, and P1151. Possible causes are:
    • Water Contamination In Connector
    • Leaking Vacuum Actuators
    • HO2S Coated With Contaminates
    • Faulty EGR Valve
    • Faulty PCV System
    • Unmetered Air Leaks Between Throttle Body & MAF Sensor
    • Engine Sealing Problems (Intake & IAC Valve)

    Turn ignition switch to OFF position. Inspect HO2S wiring harness for chafing, burned wires or other damage. Repair as necessary. Disconnect suspect HO2S connector. Connect DVOM between SIG RTN terminal and HO2S SIG terminal at suspect HO2S. Start engine and operate at 2000 RPM for 3 minutes. Perform KOER ON-DEMAND SELF-TEST  while monitoring HO2S voltage. If HO2S voltage is more than .5 volt during or at end of test, go to step  70). If voltage is .5 volt or less, replace HO2S sensor.

  40. 64) Attempt To Generate DTC P1131 Or P1151

    Start engine, and warm it to normal operating temperature. Turn ignition switch to OFF position. Disconnect suspect HO2S. Connect a jumper wire between HO2S SIG terminal at suspect HO2S harness connector and negative battery terminal. Perform KOER on-demand self-test. See KOER ON-DEMAND SELF-TEST  under QUICK TEST. If DTC P1131 or P1151 is present, remove jumper wire and go to next step. If DTC P1131 or P1151 is not present, check PCM connector and repair as necessary. If connector is okay, replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Program PCM. See FLASH VEHICLE IDENTIFICATION BLOCK PROCEDURE .

  41. 65) HO2S Voltage Check

    Leave HO2S disconnected. Connect DVOM between HO2S SIG terminal and SIG RTN terminal at suspect HO2S harness connector. Disconnect any vacuum hose from vacuum tree. Start engine and operate at 2000 RPM. If DVOM reads less than .4 volt within 30 seconds, go to step  70). If DVOM does not read .4 volt within 30 seconds, replace HO2S.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 65) to step 70). No test procedures have been omitted.

  42. 70) Monitor HO2S PID For Proper Switching During Wiggle Test

    Connect scan tool to Data Link Connector (DLC). Start engine and allow to idle. Ensure engine is at normal operating temperature. Using scan tool, select suspect HO2S PID from PID/DATA MONITOR & RECORD menu. Monitor suspect HO2S PID value while wiggling and bending small sections of wiring harness between suspect HO2S and PCM. If suspect HO2S PID voltage stays high (more than .45 volt) or stays low (less than .45 volt), isolate fault and repair as necessary. If suspect HO2S PID voltage switches, go to next step.

  43. 71) Monitor HO2S PID Switching During Test Drive

    Using an assistant, test drive vehicle under various conditions while observing suspect HO2S PID. If suspect HO2S PID voltage switches from more than .45 volts DC and then to less than .45 volts DC at least once every 3 seconds, system is okay at this time and testing is complete. If voltage does not switch from more than .45 volts DC and then to less than .45 volts DC at least once every 3 seconds, replace HO2S.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 71) to step 80). No test procedures have been omitted.

  44. 80) DTC P0136, P0156, P1137, P1138, P1157 & P1158

    DTCs P0136 and P0156 indicate that output voltage of downstream HO2S is not within set limits. KOER DTCs P1137, P1138, P1157 and P1158 indicate lack of HO2S switching. DTCs P0136, P1137 and P1138 are for HO2S-12. DTCs P0156, P1157 and P1158 are for HO2S-22. See Fig 1-Fig 3 . DTC Possible causes are:
    • Damaged Wiring Harness Or Connector
    • Exhaust System Leaks
    • Contaminated Or Defective HO2S

    Service any ignition and misfire DTCs before continuing. If no ignition or misfire DTCs are present, inspect for faults. Repair as necessary. If no faults are found, go to next step (for DTCs P0136 and P0156) or step  82) (for DTCs P1137, P1138, P1157 and P1158).

  45. 81) Check For KOER DTCs P1137, P1138, P1157 Or P1158

    Start engine, and operate at 2000 RPM for 3 minutes. Perform KOER on-demand self-test. See KOER ON-DEMAND SELF-TEST  under QUICK TEST. If DTC P1137, P1138, P1157 or P1158 is present, go to next step. If DTCs P0136 or P0156 are present, fault is unable to be duplicated at this time. Go to TEST Z .

  46. 82) Check Exhaust System For Leaks

    DTCs P0136 and P0156 can be set when leaks exist in exhaust system between engine and rear of catalytic converter. Possible causes are:
    • Incorrect HO2S Torque
    • Exhaust System Leaks
    • Punctures Or Cracks In Pipes Leading To Or In Catalytic Converter

    Inspect exhaust system including catalytic converter and HO2S. Repair as necessary. If exhaust system is okay, go to next step.

  47. 83) Check HO2S SIG Circuit For Short To VPWR Or Ground Circuits

    Turn ignition switch to OFF position. Ensure suspect HO2S is disconnected. Disconnect scan tool from DLC. Disconnect PCM connector(s). Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Measure resistance between PCM connector terminals No. B7 and C17 (SIG RTN) on LS, or terminal No. 91 (SIG RTN) on all other models and appropriate HO2S SIG terminal at PCM connector. See HO2S TERMINAL IDENTIFICATION  table.
    HO2S TERMINAL IDENTIFICATION

    Application HO2S SIG PCM Terminal No.
    LS Models
    HO2S-11 C45
    HO2S-12 C28
    HO2S-21 C44
    HO2S-22 C29
    All Other Models
    HO2S-11 60
    HO2S-12 35
    HO2S-21 87
    HO2S-22 61

    Measure resistance between appropriate HO2S SIG terminal at PCM connector and PCM connector terminals No. A32 and A33 (VPWR), C20 (VREF) and A24, A25, A26 and A27 (PWR GND) on LS and between appropriate HO2S SIG terminal at PCM connector and PCM connector terminals No. 71 (VPWR), 90 (VREF) and 103 (PWR GND) on all other models. If all resistance readings are more than 10 k/ohms, go to next step. If any resistance reading is 10 k/ohms or less, repair short circuit.

  48. 84) Check HO2S SIG & SIG RTN Circuits For Open

    Measure resistance between HO2S SIG terminal at suspect HO2S harness connector and appropriate HO2S SIG terminal at PCM connector. See HO2S TERMINAL IDENTIFICATION  table. Measure resistance between PCM connector terminals No. B17 and C17 (SIG RTN) on LS or terminal No. 91 (SIG RTN) on all other models and SIG RTN terminal at suspect HO2S harness connector. If any resistance reading is 5 ohms or more, repair open circuit. If both resistance readings are less than 5 ohms, go to next step.

  49. 85) Check HO2S Circuit Voltage

    Turn ignition switch to OFF position. Connect scan tool to DLC. Reconnect suspect HO2S and PCM connectors. Turn ignition switch to ON position. Using scan tool, select appropriate HO2S PID from PID/DATA MONITOR & RECORD menu. HO2S DTC identification is as follows:
    • DTCs P0136, P1137 and P1138 are for HO2S-12.
    • DTCs P0156, P1157 and P1158 are for HO2S-22.

    Refer to illustrations for HO2S identification. See Fig 1-Fig 3 . If PID voltage is more than 1.5 volts, go to step  88). If PID voltage is 1.5 volts or less, go to next step.

  50. 86) Check HO2S Ground Circuit In PCM

    Turn ignition switch to OFF position. Disconnect PCM connector(s). On LS, measure resistance between PCM connector terminals No. A24, A25, A26 and A27 (PWR GND) and No. B17 and C17 (SIG RTN). On all other models, measure resistance between PCM connector terminals No. 103 (PWR GND) and No. 91 (SIG RTN). If any resistance reading is less than 5 ohms, reconnect PCM connector and go to next step. If all resistance readings are 5 ohms or more, replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Program PCM. See FLASH VEHICLE IDENTIFICATION BLOCK PROCEDURE .

  51. 87) HO2S Circuit Check

    Connect a jumper wire between VPWR and HO2S SIG terminals at suspect HO2S harness connector. Turn ignition switch to ON position. Using scan tool, select appropriate HO2S PID from PID/DATA MONITOR & RECORD menu. If PID voltage is more than 1.5 volts, replace HO2S. If PID voltage is 1.5 volts or less, replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Program PCM. See FLASH VEHICLE IDENTIFICATION BLOCK PROCEDURE .

  52. 88) Check For Over Voltage On HO2S Circuit In PCM

    Turn ignition switch to ON position. Measure voltage between SIG RTN terminal at suspect HO2S harness connector and negative battery terminal. Measure voltage between HO2S SIG terminal at suspect HO2S harness connector and negative battery terminal. If any voltage reading is more than 1.5 volts, replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Program PCM. See FLASH VEHICLE IDENTIFICATION BLOCK PROCEDURE . If both voltage readings are 1.5 volts or less, replace HO2S.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 88) to step 100). No test procedures have been omitted.

  53. 100) KOER DTC P1127

    DTC P1127 indicates that downstream HO2S heaters were not cycled on during KOER self-test due to exhaust temperatures falling below a minimum calibrated value. Possible causes are:
    • Engine Not At Operating Temperature
    • Exhaust System Too Cool

    Connect scan tool to Data Link Connector (DLC). Using scan tool, access all HO2S HTR PIDs from PID/DATA MONITOR & RECORD menu. If all HO2S HTR PIDs switch or indicate ON, perform KOER ON-DEMAND SELF-TEST  under QUICK TEST. If any HO2S HTR PIDs do not switch or indicate OFF, operate engine until all HO2S HTR PIDs switch or indicate ON. Repeat KOER ON-DEMAND SELF-TEST  under QUICK TEST.

    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 100) to step 110). No test procedures have been omitted.

  54. 110) KOER P1128 & P1129

    These DTCs indicate that during KOER self-test, one or both HO2S signals were crossed from bank to bank. DTC P1128 refers to HO2S in front of converter. DTC P1129 refers to HO2S behind converter. Possible causes for these faults are:
    • Crossed HO2S Connectors
    • Crossed HO2S Wiring At HO2S Connector
    • Crossed HO2S Wiring At PCM Connector

    Turn ignition switch to OFF position. Disconnect suspect HO2S. Inspect connector for indication of crossed wires or incorrect installation. Repair as necessary. If no faults are found, go to next step.

  55. 111) Verify Proper HO2S SIG Terminal Location

    Disconnect PCM connector(s). Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Disconnect both suspect HO2S connectors. HO2S DTC identification is as follows:
    • DTC P1128 is for HO2S-11 and HO2S-21.
    • DTC P1129 is for HO2S-12 and HO2S-22.

    Refer to illustrations for HO2S identification. See Fig 1-Fig 3 . Measure resistance between HO2S SIG terminal at suspect HO2S harness connector and appropriate HO2S SIG terminal at PCM connector. See HO2S TERMINAL IDENTIFICATION  table. If resistance is less than 5 ohms, fault is intermittent and cannot be duplicated at this time. If resistance is 5 ohms or more, HO2S wiring is crossed. Recheck all HO2S wiring terminal locations at PCM and HO2S connectors. Repair as necessary.

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