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Home >> Mazda >> 1999 >> B2500 SX, Automatic >> Repair and Diagnosis >> External Pages >> Different car >> Section 4 (Engine Controls - Self-Diagnostics - EEC-V - 6.8L (99S E Series & 99S F350 To F550)) >> System Tests >> Test H: Fuel Control >> Diagnostic Aids

Diagnostic Aids

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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: Test procedure begins with step 20)  . No test procedures have been omitted.

  1. 20) Perform KOER Self-Test
    Perform KOER ON-DEMAND SELF-TEST . If DTC P1127, P1128 or P1129 is present, go to appropriate system test. See DIAGNOSTIC TROUBLE CODE (DTC) DEFINITIONS . If DTC P1127, P1128 or P1129 is not present, go to next step.

  2. 21) DTC P0133 & P0153

    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 on. 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 614 or less, go to next step. If measured value is more than 614, 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 CYCLES  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.

  3. 22) Check For HO2S Contamination

    Check following possibilities as potential source of contamination:
    • Use of unapproved silicon sealers.
    • Use of unapproved cleaners.
    • Fuel contaminated by silicon additives.
    • Fuel contaminated by lead.
    • Excessive oil burning.
    • Antifreeze leaking internally.

    If none of these conditions are present, go to next step. If any of these conditions are present, repair source of contamination as necessary. Replace HO2S. Change oil filter. Perform HO2S MONITOR REPAIR VERIFICATION DRIVE CYCLE. See FUEL MONITOR OR HO2S MONITOR REPAIR VERIFICATION DRIVE CYCLE under DRIVE CYCLES  under ADDITIONAL SYSTEM FUNCTIONS.

  4. 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.
    • EGR system.
    • PCV system.
    • Poorly seated oil dip stick and/or dipstick tube.

    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 CYCLES  under ADDITIONAL SYSTEM FUNCTIONS.

  5. 24) Check HO2S Circuits

    Turn ignition off. Disconnect suspect HO2S wiring harness connector. Connect a jumper wire between HO2S SIG and VPWR terminals at suspect HO2S wiring harness connector. See Fig 4 or Fig 5 . Turn ignition on. Using scan tool, select appropriate HO2S PID from PID/DATA monitor 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 CYCLES  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.

  6. 25) Check HO2S Signal Circuit Resistance

    Turn ignition off. Disconnect PCM 104-pin connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Measure resistance of HO2S SIG circuit between suspect HO2S PCM connector pin and HO2S SIG terminal at HO2S wiring harness connector. See HO2S PCM PIN IDENTIFICATION (CONTOUR, COUGAR & MYSTIQUE)  or HO2S PCM PIN IDENTIFICATION (EXCEPT CONTOUR, COUGAR & MYSTIQUE)  table. Also measure resistance between PCM connector pin No. 91 and SIG RTN terminal at suspect HO2S wiring 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 CYCLES  under ADDITIONAL SYSTEM FUNCTIONS.
    HO2S PCM PIN IDENTIFICATION (CONTOUR, COUGAR & MYSTIQUE) (1)

    Application HO2S SIG PCM Pin No. HO2S HTR PCM Pin No.
    HO2S-11 60 73
    HO2S-12 35 100
    HO2S-21 87 99
    HO2S-22 61 101
    (1) SIG RTN circuit is PCM pin No. 91. VPWR circuit is PCM pin No. 71.
    HO2S PCM PIN IDENTIFICATION (EXCEPT CONTOUR, COUGAR & MYSTIQUE) (1)

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

  7. 26) Check HO2S For Short Circuit

    Disconnect scan tool from Data Link Connector (DLC). Measure resistance between PCM connector pin No. 71 (VPWR) and appropriate HO2S SIG PCM connector pin. Also measure resistance between appropriate HO2S SIG PCM connector pin and pin No. 91 (SIG RTN). If all resistance readings are more than 10,000 ohms, replace PCM. Perform HO2S MONITOR REPAIR VERIFICATION DRIVE CYCLE. See FUEL MONITOR OR HO2S MONITOR REPAIR VERIFICATION DRIVE CYCLE under DRIVE CYCLES  under ADDITIONAL SYSTEM FUNCTIONS. If any resistance reading is 10,000 ohms or less, repair short circuit. Perform HO2S MONITOR REPAIR VERIFICATION DRIVE CYCLE. See FUEL MONITOR OR HO2S MONITOR REPAIR VERIFICATION DRIVE CYCLE under DRIVE CYCLES  under ADDITIONAL SYSTEM FUNCTIONS.

  8. 27) DTC P0131 & P0151: Contaminated HO2S/Voltage Shift

    These DTCs are set when HO2S generates negative voltage. Possible causes are:
    • Crossed HO2S SIG / SIG RTN circuit wiring.
    • HO2S contaminated with water, fuel, etc.

    DTC P0131 is for HO2S-11. See Fig 1-Fig 3 . DTC P0153 is for HO2S-21. See Fig 2 or Fig 3 . Check for moisture in HO2S connector and repair as necessary. If connector is dry, go to next step.

  9. 28) Verify Wiring Is In Proper Pin Location

    Ensure ignition is off. Disconnect suspect HO2S. Disconnect PCM 104-pin connector. Inspect connectors for loose, damaged or corroded terminals. Repair as necessary. Measure resistance between PCM connector pin No. 60 (DTC P0131) or No. 87 (DTC P0151) and HO2S SIG terminal at suspect HO2S wiring harness connector. Also measure resistance between PCM connector pin No. 91 (SIG RTN) and SIG RTN terminal at suspect HO2S wiring harness connector. 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.

  10. 30) DTC P0135, P0141, P0155 Or P0161

    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 P0135 is for HO2S-11.
    • DTC P0141 is for HO2S-12.
    • DTC P0155 is for HO2S-22.
    • 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.

  11. 31) Perform KOEO Self-Test

    Start engine and operate at 2000 RPM for one minute. Turn ignition off. 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 .

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

    Turn ignition off. Disconnect suspect HO2S. Inspect wiring harness for damage and repair as necessary. Turn ignition on. Measure voltage between SIG RTN and VPWR terminals at suspect HO2S wiring harness connector. If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, check circuit fuse. Replace as necessary. If fuse is okay, repair open circuit.

  13. 33) Check HO2S Heater Resistance

    Turn ignition off. 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.

  14. 34) Check HO2S Case For Short Circuit

    Measure resistance between HO2S HTR terminal at HO2S and HO2S case. Measure resistance between HO2S HTR terminal and SIG RTN terminal at HO2S. Also measure resistance between VPWR terminal at HO2S and HO2S case. If all resistance readings are more than 10,000 ohms, go to next step. If any resistance reading is 10,000 ohms or less, replace HO2S.

  15. 35) Check For Short Circuit

    Disconnect scan tool from DLC. Disconnect PCM 104-pin connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Measure resistance between HO2S HTR terminal and SIG RTN and VPWR terminals at suspect HO2S wiring harness connector. See Fig 4 or Fig 5 . If both resistance readings are more than 10,000 ohms, go to next step. If any resistance reading is 10,000 ohms or less, repair short circuit.

  16. 36) Check For Open Circuit

    Leave ignition off and HO2S disconnected. Measure resistance between HO2S HTR terminal at suspect HO2S wiring harness connector and appropriate HO2S HTR pin at PCM connector. See HO2S PCM PIN IDENTIFICATION (CONTOUR, COUGAR & MYSTIQUE)  or HO2S PCM PIN IDENTIFICATION (EXCEPT CONTOUR, COUGAR & MYSTIQUE)  table. See Fig 4 or Fig 5 . If resistance is 4 ohms or more, repair open circuit or excessive resistance in wiring harness. If resistance is less than 4 ohms, replace PCM.
    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.

  17. 40) DTCs P1130, P1150, P1131, P1151, P1132 Or P1152

    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 fuel system has reached maximum compensation and HO2S is not switching at the adaptive limits. Possible causes are:
    • Fuel system malfunction.
    • EGR system malfunction.
    • Air intake or vacuum system leak.
    • Engine oil level too high.
    • Incorrect cam timing.
    • Restricted air cleaner.
    • Faulty PCV system.
    • Excessive internal engine wear.

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

  18. 41) DTC P0171, P0172, P0174 Or P0175

    DTCs P0171 and P0174 indicate air/fuel ratio is correcting rich for an overly lean condition. DTCs P0172 and P0175 indicate air/fuel ratio is correcting lean for an overly rich condition. Possible causes are:
    • Fuel system malfunction.
    • EGR system malfunction.
    • Air intake or vacuum system leak.
    • Engine oil level too high.
    • Incorrect cam timing.
    • Restricted air cleaner.
    • Faulty PCV system.
    • Excessive internal engine wear.

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

  19. 42) Perform KOER Self-Test

    Turn ignition off. Connect scan tool to DLC. Disconnect fuel vapor hose from intake manifold and plug fitting at intake manifold. Start engine, and operate at 2000 RPM for 5 minutes. 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 (DTC) DEFINITIONS .
    • If DTC P0131 or P0151 is present in continuous memory, go to step  27).
    • If DTC P1130, P1131, P1150 or P1151 is present, go to next step.
    • If DTC P1130, P1132, P1150 or 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 DTC P1132 or P1152 is no longer present, go to  TEST HX, step 22).
    • If DTC P1131 or P1151 is no longer present, go to  TEST HX, step 58).
    • On all others without reoccurring DTCs, fault is intermittent. Go to TEST Z .

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

    Disconnect suspect HO2S. Turn ignition on. Using scan tool, select appropriate HO2S PID from PID/DATA monitor menu. Connect a jumper wire between HO2S SIG and VPWR terminals at suspect HO2S wiring harness connector. If arcing occurs (indicating a short), 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).

  21. 44) Check Circuit Resistance

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

  22. 45) Check For Open Circuit

    Turn ignition off. Disconnect PCM connector. Measure resistance between PCM connector pin No. 91 (SIG RTN) and SIG RTN terminal at suspect HO2S wiring harness connector. If resistance is less than 5 ohms, replace PCM. If resistance is 5 ohms or more, repair open circuit.

  23. 46) Check Resistance Of HO2S SIG & Ground Circuits

    Turn ignition off. Disconnect PCM connector. 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 wiring harness connector and appropriate HO2S SIG pin at PCM connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit.

  24. 47) Check HO2S Circuit For Short To Ground

    Measure resistance between PCM connector pins No. 91 and 103 and appropriate HO2S SIG pin at PCM connector. If both resistance readings are more than 10,000 ohms, go to next step. If any resistance reading is 10,000 ohms or less, repair short circuit.

  25. 48) Check HO2S For Short To G0ound

    Reconnect suspect HO2S connector. Measure resistance between PCM connector pins No. 91 and 103 and suspect HO2S SIG pin at PCM connector: If any resistance reading is 10,000 ohms or less, replace HO2S. If both resistance readings are more than 10,000 ohms, replace PCM.

  26. 49) Check HO2S PID

    Ensure ignition is off. Disconnect suspect HO2S connector. Turn ignition on. Using scan tool, select appropriate HO2S PID from PID/DATA monitor menu. If PID voltage is more than .2 volt, go to next step. If PID voltage is .2 volt or less, go to step  51).

  27. 50) Check For Short To Power

    Turn ignition off. Disconnect scan tool from DLC. Disconnect PCM 104-pin connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Measure resistance between PCM connector pin No. 71 (VPWR) and suspect HO2S SIG pin at PCM connector. Also measure resistance between suspect HO2S SIG and HO2S HTR pins at PCM connector. HO2S PCM PIN IDENTIFICATION (CONTOUR, COUGAR & MYSTIQUE)  or HO2S PCM PIN IDENTIFICATION (EXCEPT CONTOUR, COUGAR & MYSTIQUE)  table. If both resistance readings are more than 10,000 ohms, replace PCM. If any resistance reading is 10,000 ohms or less, repair short to power.

  28. 51) Check For Shorted HO2S

    Reconnect suspect HO2S connector. Turn ignition on. Using scan tool, select appropriate HO2S PID from PID/DATA monitor menu. If PID voltage is more than .45 volt, replace HO2S. If PID voltage is .45 volt or less, reconnect all connectors and go to next step.

  29. 52) Check Fuel Pressure

    Release fuel system pressure. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. With ignition off, install fuel pressure gauge. Verify vacuum source to fuel pressure regulator (returnable fuel system only). Using scan tool, access OUTPUT TEST MODE. Command fuel pump ON. Note 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 (vehicles with returnable fuel system) or go to step  55) (vehicles with returnless fuel system). See FUEL SYSTEM IDENTIFICATION  table.
    FUEL SYSTEM IDENTIFICATION

    Application Fuel System
    Continental, Escort & Tracer Electronic Returnless
    Ranger Mechanical Returnless
    All Others (1) Returnable
    (1) Fuel is returned to fuel tank by means of return line from fuel rail.

  30. 53) Check System Ability To Hold Fuel Pressure

    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).

  31. 54) Check Ability To Hold Fuel Pressure

    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. If fuel pressure remains within 5 psi (34 kPa) of maximum pressure for at least 10 seconds, go to next. If fuel pressure drops more than 5 psi, go to step  58).

  32. 55) Check Injector Fault PIDs

    Turn ignition on. Using scan tool, select INJ1F-INJ10F PIDs from PID/DATA monitor menu. If misfire DTCs are present, select only injector fault PIDs that correspond to misfire DTCs. If PID value indicates a injector fault, go to next step. If PID values do not indicate injector fault, go to step  59).

  33. 56) Check Fuel Injector & Circuit Resistance

    Turn ignition off. Disconnect PCM 104-pin connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Measure and record resistance between PCM connector pin No. 71 and suspect fuel injector circuit pin at PCM connector. Use injector fault PID noted in step 55)  to determine fuel injector circuits that require testing. See FUEL INJECTOR PCM PIN IDENTIFICATION  table. Resistance should be 11-18 ohms. If resistance is not as specified, go to next step. If resistance is as specified, replace PCM.
    NOTE: If misfire DTCs are present with fuel control DTCs, use misfire DTCs to determine which fuel injector circuits require testing.
    FUEL INJECTOR PCM PIN IDENTIFICATION

    Injector No. PCM Pin No.
    Contour 2.5L, Cougar 2.5L & Mystique 2.5L
    1 70
    2 96
    3 20
    4 95
    5 93
    6 94
    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.

  34. 57) Check Resistance Of Fuel Injector Circuit

    Turn ignition off. Disconnect suspect fuel injector connector. Measure resistance between PCM connector pin No. 71 and VPWR terminal at suspect fuel injector wiring harness connector. See Fig 6. Also measure resistance between fuel injector signal circuit terminal(s) at PCM connector and same fuel injector circuit terminal at suspect fuel injector wiring 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.

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

    Measure resistance between PCM connector fuel injector signal pin(s) and pins No. 71 and 103. Also measure resistance between PCM connector fuel injector signal pin(s) and ground. If all resistance readings are more than 10,000 ohms, go to next step. If any resistance reading is less than 10,000 ohms, repair short circuit.

  36. 59) Check Fuel Injector Flow & Leakage

    Turn ignition off. 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 P1172 and P1175, fault is intermittent. Go to TEST Z .

  37. 60) Check Secondary Air Injection

    If vehicle is not equipped with secondary air injection, go to next step. Turn ignition off. 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 . If DTC P1131 or P1151 is present, reconnect air injection hoses and go to next step. If DTC P1131 or P1151 is not present, check secondary air injection system. See  TEST HM, step 7).

  38. 61) Check Air Induction System

    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.

  39. 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).

  40. 63) Check HO2S Integrity

    Any vacuum or air leaks can cause DTCs P1130, P1131, P1150, and P1151. Possible causes are:
    • Leaking vacuum actuators.
    • HO2S coated with contaminates.
    • Faulty EGR valve.
    • Faulty PCV system.
    • Unmetered air leaks between throttle body and MAF sensor.
    • Engine sealing problems (intake and IAC valve).

    Turn ignition off. 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.

  41. 64) Perform KOER Self-Test

    Start engine, and warm it to normal operating temperature. Turn ignition off. Disconnect suspect HO2S. Connect a jumper wire between HO2S SIG terminal at suspect HO2S wiring harness connector and negative battery terminal. Perform KOER ON-DEMAND SELF-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.

  42. 65) HO2S Check

    Leave HO2S disconnected. Connect DVOM between HO2S SIG terminal and SIG RTN terminal at suspect HO2S wiring 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.

  43. 70) Monitor HO2S PID

    Start engine and allow to idle. Ensure engine is at normal operating temperature. Using scan tool, select HO2S PID from PID/DATA monitor menu. Observe PID value while wiggling and bending wiring harness between HO2S and PCM. If PID voltage stays high (more than .45 volt) or stays low (less than .45 volt), isolate fault and repair as necessary. If PID voltage switches, go to next step.

  44. 71) Monitor HO2S PID During Test Drive

    Using an assistant, test drive vehicle under various conditions while observing HO2S PID. If PID voltage switches from about .4 to .6 volt, system is okay at this time and testing is complete. If voltage does not switch from about .4 to .6 volt, 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.

  45. 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 misfire DTCs before continuing. If no 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).

  46. 81) Perform KOER Self-Test

    Start engine, and operate at 2000 RPM for 3 minutes. Perform KOER ON-DEMAND SELF-TEST . If DTC P1137, P1138, P1157 or P1158 is present, go to next step. If specified DTCs are not present, fault is intermittent. Go to TEST Z .

  47. 82) Check Exhaust System

    Leaks in exhaust system between engine and rear of catalytic converter can cause DTCs P0136 and P0156. Possible causes are:
    • Incorrect HO2S torque.
    • Exhaust system leaks.

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

  48. 83) Check HO2S SIG Circuit For Short Circuit

    Turn ignition off. Ensure suspect HO2S is disconnected. Disconnect scan tool from DLC. Disconnect PCM 104-pin connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Measure resistance between PCM connector pin No. 91 (SIG RTN) and appropriate HO2S SIG pin at PCM connector as follows:
    • HO2S-12, PCM connector pin No. 35.
    • HO2S-22, connector pin No. 61.

    Also measure resistance between appropriate HO2S SIG pin at PCM connector and PCM connector pins No. 71 (VPWR), 90 (VREF) and 103 (PWR GND). If all resistance readings are more than 10,000 ohms, go to next step. If any resistance reading is 10,000 ohms or less, repair short circuit.

  49. 84) Check For Open Circuit

    Measure resistance between HO2S SIG terminal at suspect HO2S wiring harness connector and appropriate HO2S SIG pin at PCM connector as follows:
    • HO2S-12, PCM connector pin No. 35.
    • HO2S-22, PCM connector pin No. 61.

    Also measure resistance between PCM connector pin No. 91 (SIG RTN) and SIG RTN terminal at suspect HO2S wiring 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.

  50. 85) Check HO2S Circuit

    Turn ignition off. Connect scan tool to DLC. Reconnect suspect HO2S and PCM connectors. Turn ignition on. Using scan tool, select appropriate HO2S PID from PID/DATA monitor 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.

  51. 86) Check Ground Circuit In PCM

    Turn ignition off. Disconnect PCM connector. Measure resistance between PCM connector pins No. 103 (PWR GND) and No. 91 (SIG RTN). If resistance is less than 5 ohms, reconnect PCM connector and go to next step. If resistance is 5 ohms or more, replace PCM.

  52. 87) Check HO2S PID

    Connect a jumper wire between VPWR and HO2S SIG terminals at suspect HO2S wiring harness connector. Turn ignition on. Using scan tool, select appropriate HO2S PID from PID/DATA monitor menu. If PID voltage is more than 1.5 volts, replace HO2S. If PID voltage is 1.5 volts or less, replace PCM.

  53. 88) Check For HO2S Voltage

    Turn ignition on. Measure voltage between SIG RTN terminal at suspect HO2S wiring harness connector and negative battery terminal. Also measure voltage between HO2S SIG terminal at suspect HO2S wiring harness connector and negative battery terminal. If any voltage reading is more than 1.5 volts, replace PCM. 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.

  54. 100) KOER DTC P1127

    DTC P1127 indicates that HO2S heater was not on during KOER self-test and testing of HO2S did not occur. Possible cause is cool exhaust system. Connect scan tool to DLC. Using scan tool, access all HO2S heater PIDs. If all PIDs indicate ON, repeat QUICK TEST . If any PIDs indicate OFF, operate engine until all PIDs are on. Repeat 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.

  55. 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 off. 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.

  56. 111) Verify Proper HO2S SIG Pin Location

    Disconnect PCM 104-pin connector. 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 wiring harness connector and appropriate HO2S SIG pin at PCM connector as follows:

    • HO2S-11, PCM connector pin No. 60.
    • HO2S-12, PCM connector pin No. 87.
    • HO2S-21, PCM connector pin No. 35.
    • HO2S-22, PCM connector pin No. 61.

    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 pin locations at PCM and HO2S connectors. Repair as necessary.

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