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Home >> Mazda >> 2002 >> Tribute LX, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 27 (Engine Controls - Self-Diagnostics - 2.5L) >> Diagnostic Tests >> DTC P0171, P0172, P0174 Or P0175: Fuel Trim System & DTC P1130, P1131, P1132, P1150, P1151 Or P1152: Ho2S Not Switching >> Diagnosis & Repair Procedure

Diagnosis & Repair Procedure

WARNING: This page is about a different car, the 2002 Mazda 626. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ensure FREEZE FRAME DATA has been recorded. Check for related service bulletins. Repair as necessary and go to next step.
  2. Check intake air system for leaks, obstruction or damage. Check air cleaner element and air cleaner housing for blockage. Check PCV system operation. Check for vacuum leaks. Repair or replace as necessary and go to step  47 . If all systems are operating properly, go to next step.
  3. Turn ignition off. Disconnect fuel vapor hose from intake manifold and plug fitting at intake manifold. Start engine, and operate it at 2000 RPM for 5 minutes. Allow engine to idle. Using scan tool, perform KOER self-test and check for DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. If DTC P1127, P1131, P1132, P1151 and P1152 are present, perform following:
    • If DTC P1127 is present, go to DTC P1127: COLD EXHAUST  .
    • If DTC P1131 or P1151 and continuous memory DTC P1130 or P1150 are present, go to next step.
    • If DTC P1132 or P1152 and continuous memory DTC P1130 or P1150 are present, go to step  9 .

    If DTC P1127, P1131 or P1132 are not present, perform following:

    4. NOTE: When performing following step, if spark occurs, remove fused jumper wire, check for blown ENGINE fuse (10-amp) from junction box located at left side of instrument panel, and go to step  8 .
  4. Disconnect front HO2S. Check for loose, damaged or corroded connector terminals. Repair as necessary. Turn ignition on. Using scan tool, check O2S11 PID data. Connect a fused jumper wire between front HO2S harness connector Black/White wire and Red wire terminals. Read scan tool and disconnect fused jumper wire. If HO2S voltage is greater than 1.3 volts, check front HO2S ground circuit and go to next step. If 1.3 volts or less is present, check for open or short to ground in suspect wire harness or PCM. See WIRING DIAGRAMS article. Go to step  7 .
  5. Turn ignition off. Backprobing at PCM connector, measure resistance between PCM connector terminal No. 91 (Black/Yellow wire) and front HO2S harness connector Black/Yellow wire terminal. See Fig 1 . If resistance is less than 5 ohms, go to step  13 . If resistance is 5 ohms or more, go to next step.
  6. Disconnect PCM connector. Measure resistance between PCM harness connector terminal No. 91 (Black/Yellow wire) and front HO2S harness connector Black/Yellow wire terminal. See Fig 1 . If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair short to ground in Black/Yellow wire. See WIRING DIAGRAMS article. Go to step  47 .
  7. Disconnect PCM connector. Check for loose, damaged or corroded connector terminals. Repair as necessary. Measure resistance between PCM harness connector terminal No. 91 (Black/Yellow wire) and suspect front HO2S harness connector Black/Yellow wire terminal. For right front HO2S, measure resistance between PCM harness connector terminal No. 60 (Red wire) and right front HO2S harness connector Red wire terminal. For left front HO2S, measure resistance between PCM harness connector terminal No. 87 (Black wire) and left front HO2S harness connector Black wire terminal. If resistance at all circuits is less than 5 ohms, go to next step. If resistance at any circuit is 5 ohms or more, repair open in appropriate circuit. See WIRING DIAGRAMS article. Go to step  47 .
  8. On right front HO2S, measure resistance between PCM harness connector terminal No. 60 (Red wire) and terminals No. 24 (Black/Blue wire), No. 51 (Black/Blue wire), No. 76 (Black/Red wire), No. 77 (Black/Blue wire), No. 91 (Black/Yellow wire) and No. 103 (Black/Blue wire), individually. See Fig 1 . On left front HO2S, measure resistance between PCM harness connector terminal No. 87 (Black wire) and terminals No. 24 (Black/Blue wire), No. 51 (Black/Blue wire), No. 76 (Black/Red wire), No. 77 (Black/Blue wire), No. 91 (Black/Yellow wire) and No. 103 (Black/Blue wire), individually. If all resistance readings are greater than 10 k/ohms, go to next step. If any resistance reading is 10 k/ohms or less, repair short between Red wire (on right front HO2S; Black wire at left front HO2S) and suspect ground circuit. See WIRING DIAGRAMS article. Go to step  47 .
  9. Reconnect front HO2S connections. Measure resistance between ground and PCM harness connector terminals No. 24 (Black/Blue wire), No. 60 (Red wire), No. 87 (Black wire), No. 91 (Black/Yellow wire) and No. 103 (Black/Blue wire), individually. If all resistance readings are greater than 10 k/ohms, go to next step. If any resistance reading is 10 k/ohms or less, replace suspect HO2S and go to step  47 .
  10. Disconnect suspect front HO2S connector. Check for loose, damaged or corroded connector terminals. Repair as necessary. Turn ignition on. Using scan tool, check O2S11 PID (on right front HO2S; O2S21 PID on left front HO2S) data. If O2S11 PID (on right front HO2S; O2S21 PID on left front HO2S) voltage is greater than .2 volt, a short to power is present, go to next step. If O2S11 PID (on right front HO2S; O2S21 PID on left front HO2S) voltage is .2 volt or less, go to step  12 .
  11. Turn ignition off. Disconnect scan tool from DLC. Disconnect PCM connector. Check for loose, damaged or corroded connector terminals. Repair as necessary. On right front HO2S, measure resistance between PCM harness connector terminal No. 60 (Red wire) and terminals No. 71 (Red/Black wire), No. 93 (Brown wire) and No. 97 (Red/Black wire), individually. See Fig 1 . On left front HO2S, measure resistance between PCM harness connector terminal No. 87 (Black wire) and terminals No. 71 (Red/Black wire), No. 94 (White/Blue wire) and No. 97 (Red/Black wire), individually. If all resistance readings are greater than 10 k/ohms, go to next step. If any resistance reading is 10 k/ohms or less, replace HO2S and go to next step.
  12. Reconnect front HO2S connector. Turn ignition on. Using scan tool, check O2S11 PID (on right front HO2S; O2S21 PID on left front HO2S) data. If O2S11 PID (on right front HO2S; O2S21 PID on left front HO2S) voltage is greater than .45 volt, replace front HO2S and go to step  47 . If O2S11 PID (on right front HO2S; O2S21 PID on left front HO2S) voltage is .45 volt or less, reconnect all connections and go to next step.
  13. Check for correct fuel line pressure. See SYSTEM & COMPONENT TESTING - MIATA, MILLENIA, MPV, PROTEGE, PROTEGE5 & 626 article. Fuel pressure should be 37-46 psi (2.6-3.2 kg/cm2 ). If fuel system pressure is not as specified, go to next step. If fuel system pressure is as specified, go to step  23 .
  14. If in addition to low fuel pressure, customer all complains of lack of power, check for Pressure Regulator Control (PRC) solenoid valve malfunction, damaged fuel system related vacuum lines, damaged PRC solenoid valve circuits and PCM malfunction. If all components are okay, turn ignition off. Disconnect PRC solenoid harness connector. Turn ignition on. Measure voltage between ground and PRC solenoid harness connector Red/Black wire terminal. If more than 10.5 volts is present, go to next step. If 10.5 volts or less are present, repair open circuit. See WIRING DIAGRAMS article. Go to step  47 .
  15. Turn ignition off. Disconnect PCM connector. Check for loose, damaged or corroded connector terminals. Repair as necessary. Measure resistance between PCM harness connector terminal No. 19 (Blue/Yellow wire) and PRC solenoid harness connector Blue/Yellow wire terminal. See Fig 1 . If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open Blue/Yellow wire. See WIRING DIAGRAMS article. Go to step  47 .
  16. Disconnect scan tool. Measure resistance between PCM harness connector terminal No. 19 (Blue/Yellow wire) and terminals No. 24 (Black/Blue wire), No. 71 (Red/Black wire), No. 77 (Black/Blue wire), No. 91 (Black/Yellow wire) and No. 97 (Red/Black wire), individually. If each measurement is more than 10 k/ohms, go to next step. If any measurement is 10 k/ohms or less, repair shorted suspect circuits. See WIRING DIAGRAMS article. Go to step  47 .
  17. Check vacuum line between intake manifold port and PRC solenoid valve for blockage, kinks or cracks. Replace as necessary and go to step  47 . If vacuum line is okay, reconnect vacuum line to intake manifold port only and go to next step.
  18. Connect vacuum gauge to PRC solenoid valve vacuum line. Start engine. If vacuum signal is present, go to next step. If vacuum signal is not present, reconnect all components and go to step  40 .
  19. Turn ignition off. Check vacuum line between fuel pressure regulator and PRC solenoid valve for blockage, kinks or cracks. Replace as necessary and go to step  47 . If vacuum line is okay, go to next step.
  20. Turn ignition off. Disconnect vacuum line located between PRC solenoid valve and fuel pressure regulator at fuel pressure regulator. Install vacuum gauge. Disconnect vacuum line located between PRC solenoid valve and intake manifold at intake manifold. Install vacuum pump. Apply 8-10 in. Hg of vacuum. If vacuum is present at vacuum gauge, go to next step. If no vacuum is not present, replace PRC solenoid valve and go to step  47 .
  21. Leave vacuum gauge and vacuum pump. Apply 8-10 inches of vacuum. Turn ignition on. Backprobing, momentarily jumper PCM connector terminals No. 19 (Blue/Yellow wire) and No. 103 (Black/Blue wire). See Fig 1 . If vacuum reading dropped to 0-1 inches of vacuum, go to next step. If vacuum reading did not drop, replace PRC solenoid valve and go to step  47 .
  22. Turn ignition off. Backprobing, measure voltage between PCM connector terminals No. 19 (Blue/Yellow wire) and 71 (Red/Black wire) with ignition key in ON position, engine cranking and engine running. Voltage should be 10-12 volts during cranking and 0-2 volts during all other operating conditions. If reading are as specified, replace pressure regulator and go to next step. If readings are not as specified, go to step  47 .
  23. Disconnect negative battery cable. Install fuel pressure gauge. Check for fuel leaks. Repair as necessary. Remove fuel pump relay located in main fuse block in left side of engine compartment. See Figure . Using a fused jumper wire, connect fuel pump relay socket White/Green wire and Yellow wire terminals. Reconnect negative battery cable for 10 seconds. Record maximum fuel pressure. Disconnect negative battery cable. If fuel pressure is not within 21 psi (1.5 kg/cm2 ) of maximum pressure after engine has been operating for 5 minutes, go to step  25 . If fuel pressure is within 21 psi (1.5 kg/cm2 ) of maximum pressure after engine has been operating for 5 minutes, go to next step.
  24. If fuel pressure is within 21 psi (1.5 kg/cm2 ) of maximum pressure after engine has been operating for 5 minutes, and some or all continuous DTCs P1130, P1150, P0171, P0172, P0174 and P0175 were initially set, go to step  33 . If fuel pressure is within 21 psi (1.5 kg/cm2 ) of maximum pressure after engine has been operating for 5 minutes, and engine does not start, go to step  34 . If fuel pressure is within 21 psi (1.5 kg/cm2 ) of maximum pressure after engine has been operating for 5 minutes, and misfire DTCs were also displayed along with P0171, P0172, P0174, P0175, P1130, P1131, P1132, P1150, P1151 and/or P1152, go to step  35 . If fuel pressure is within 21 psi (1.5 kg/cm2 ) of maximum pressure after engine has been operating for 5 minutes, and any other DTC is set, go to step  36 .
  25. Reconnect negative battery cable. Using a fused jumper wire, connect fuel pump relay socket White/Green wire and Yellow wire terminals until maximum fuel pressure of 49.8 psi (3.5 kg/cm2 ) is reached. If fuel pressure remains at maximum for 5 minutes, go to step  27 . If fuel pressure does not remain at maximum for 5 minutes, go to next step.
  26. Turn ignition off. With fuel pressure gauge installed, start and run engine for 10 seconds. Turn ignition off. Wait 10 seconds. Start and run engine for 10 seconds. Turn ignition off. Remove vacuum hose from fuel pressure regulator. If fuel is present in vacuum hose or fuel pressure regulator, replace fuel pressure regulator and go to step  47 . If fuel is not present in vacuum hose or fuel pressure regulator, go to step  30 .
  27. Turn ignition off. With fuel pressure gauge installed, disconnect vacuum hose at fuel pressure regulator. Plug vacuum hose. Test drive vehicle. While monitoring fuel pressure gauge, accelerate at 3/4 to full throttle. Repeat several times. If fuel pressure remains steady 37-46 psi (2.6-3.3 kg/cm2 ) while accelerating, connect vacuum hose to fuel pressure regulator and go to next step. If fuel pressure does not remain steady, go to step  30 .
  28. Turn ignition off. With fuel pressure gauge installed, install vacuum gauge to intake manifold. Start engine. While monitoring fuel pressure gauge and vacuum gauge, accelerate and decelerate engine speed. Fuel pressure should increase as vacuum decreases and decrease as vacuum increases. If fuel pressure is not as specified, go to next step. If fuel pressure is as specified, fuel pressure regulator is operating correctly. Reconnect all components. See TROUBLE SHOOTING - NO CODES article for further diagnosis.
  29. Turn ignition off. Disconnect vacuum hose at fuel pressure regulator and plug vacuum hose. Install vacuum pump to fuel pressure regulator. Start and run engine at idle. Apply vacuum to pressure regulator. Monitor fuel pressure while varying vacuum. If fuel pressure changes, go to next step. If fuel pressure does not change, replace fuel pressure regulator and go to step  47 .
  30. Turn ignition off. Use appropriate fuel injector tester to flow test fuel injectors. See SYSTEM & COMPONENT TESTING - MIATA, MILLENIA, MPV, PROTEGE, PROTEGE5 & 626 article. Follow injector tester instructions. If fuel injector flow or leakage rate is not okay, replace defective fuel injector(s) and go to step  47 . If flow rate for each fuel injector is okay, go to next step.
  31. Ensure vehicle has fuel in tank. Disconnect fuel pump connector. Check for loose, damaged or corroded connector terminals. Repair as necessary. Turn ignition on. Using scan tool, access OUTPUT TEST MODE. Command fuel pump on. Measure voltage between fuel pump harness connector Yellow wire and Black wire terminals. If more than 10.5 volts is present, exit output test mode. Reconnect fuel pump connector and go to next step. If 10.5 volts or less are present, go to step  37 .
  32. Turn ignition off. Disconnect fuel supply line at fuel rail and fuel pump. Check fuel supply line for blockage, kinks or pinching. Apply 7-46 psi (.5-3.2 kg/cm2 ) of compressed air to fuel rail side of fuel supply line. If air flows freely through fuel supply line, replace fuel pump and go to step  47 . If air does not flow freely through fuel supply line, reconnect fuel supply and go to next step.
  33. With fuel pressure gauge installed, cycle ignition switch from OFF to ON position 3 times to pressurize fuel system (DO NOT start engine). Record fuel pressure with ignition switch in ON position. If fuel pressure is not within 21 psi (1.5 kg/cm2 ) of maximum pressure for at least 10 seconds, go to next step. If fuel pressure is within 21 psi (1.5 kg/cm2 ) of maximum pressure for at least 10 seconds, and some or all continuous DTCs P1130, P1150, P0171 and P0174 were initially set, go to step  35 . If fuel pressure is within 21 psi (1.5 kg/cm2 ) of maximum pressure for at least 10 seconds, and continuous DTC P0172 and P0175 was initially set, go to step  37 .
  34. With fuel pressure gauge installed, cycle ignition switch from OFF to ON position 3 times to pressurize fuel system (DO NOT start engine). Record fuel pressure while cranking engine for 5 seconds or more. If fuel pressure does not drop more than 46 psi (3.2 kg/cm2 ) of maximum pressure, go to next step. If fuel pressure drops more than 46 psi (3.2 kg/cm2 ), electronic engine control system is not cause of no-start. Reconnect all components. See TROUBLE SHOOTING - NO CODES article for further diagnosis of no-start.
    35. NOTE: Procedure in this step will erase continuous memory DTCs.
    NOTE: If misfire DTCs are also displayed, use misfire DTCs to determine which fuel injector circuits as at fault.
  35. Turn ignition off. Disconnect PCM connector. Check for loose, damaged or corroded connector terminals. Repair as necessary. Measure resistance between PCM harness connector terminals No. 71 (Red/Black wire) and No. 97 (Red/Black wire) and PCM harness connector terminals corresponding to appropriate fuel injector circuit, individual. See Fig 1 . See FUEL INJECTOR CIRCUIT IDENTIFICATION  table. Resistance should be 12-16 ohms. If resistance is not as specified, go to next step. If resistance is as specified, go to step  38 .
    FUEL INJECTOR CIRCUIT IDENTIFICATION

    Injector No. Terminal No.
    1 75 (Blue wire)
    2 101 (Blue/White wire)
    3 74 (Blue/Red wire)
    4 100 (Violet wire)
    5 73 (White wire)
    6 99 (Yellow/Violet wire)
  36. Turn ignition off. Disconnect suspect fuel injector connector. Measure resistance between PCM harness connector terminals No. 71 (Red/Black wire) and No. 97 (Red/Black wire) and suspect fuel injector harness connector White/Red wire terminal. See Fig 1 . Measure resistance in Blue wire, Blue/White wire, Blue/Red wire, Violet wire, White wire or Yellow/Violet wire between PCM harness connector and suspect fuel injector(s) harness connector. See WIRING DIAGRAMS article. If all resistance readings are less than 5 ohms, go to next step. If any resistance reading is 5 ohms or more, repair open in appropriate circuit and go to step  47 .
  37. Measure resistance between PCM harness connector terminals No. 24 (Black/Blue wire), 71 (Red/Black wire), 97 (Red/Black wire) and 103 (Black/Blue wire), and PCM harness connector terminals corresponding to appropriate fuel injector circuit. See FUEL INJECTOR CIRCUIT IDENTIFICATION  table. Also, measure resistance between ground and PCM harness connector terminals corresponding to appropriate fuel injector circuit. See FUEL INJECTOR CIRCUIT IDENTIFICATION  table. If all resistance readings are greater than 10 k/ohms, go to next step. If any resistance reading is 10 k/ohms or less, repair short to power or short to ground in appropriate circuit. See WIRING DIAGRAMS article. Go to step  47 .
  38. With ignition off, connect non-powered, 12-volt test light between PCM harness connector terminals No. 71 (Red/Black wire) or No. 97 (Red/Black wire), and PCM harness connector terminals corresponding to appropriate fuel injector circuit. See Fig 1 . See FUEL INJECTOR CIRCUIT IDENTIFICATION  table. Crank or start engine. If test light glows dimly, system is functioning properly. Reconnect all components and go to next step. If test light does not glow dimly (no light/bright light), go to step  47 .
  39. Turn ignition off. Reconnect PCM and fuel injector connector(s). Flow test fuel injectors. See SYSTEM & COMPONENT TESTING - MIATA, MILLENIA, MPV, PROTEGE, PROTEGE5 & 626 article. If fuel injector flow or leakage rate is not okay, replace defective fuel injector(s) and go to step  47 . If flow rate for each fuel injector is okay, proceed as follows:
    • For DTCs P0171, P0174, P1130, P1131, P1150 or P1151, go to next step.
    • For DTCs P0172 or P0175, fault is intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article for further diagnosis.
    • For DTCs P1132 or P1152, go to step  43 .
  40. Check air induction tube for leaks. Check upper and lower intake manifold gaskets. Check vacuum hoses for damage and tight connections. Check PCV system for leaks. Repair as necessary and go to step  47 . If no faults are found, proceed as follows:
    • For Continuous Memory DTCs P0171, P0174, P1130 or P1150, fault is intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article for further diagnosis.
    • For DTCs P1130, P1131, P1150 or P1151, go to next step.
  41. Using compression gauge, check cylinder compression. Minimum cylinder compression should be 141 psi (8.4 kg/cm2 ) at 250 RPM and maximum difference between cylinders should be 28 psi (2.0 kg/cm2 ). If cylinder compression is not okay, repair engine as necessary and go to step  47 . If compression is okay, go to next step.
  42. Check for vacuum leak. Ensure EGR valve and PCV hose and valve are operating properly. Ensure front HO2S is not contaminated by silicone. Repair or replace as necessary. If no problem is present, turn ignition off. Inspect HO2S wiring harness for chafing, burned wires or other damage. Repair as necessary. Disconnect suspect HO2S connector. Measure voltage between front HO2S connector Black/Yellow wire and Red wire terminals. Start engine and operate at 2000 RPM for 3 minutes. If HO2S voltage is greater than .5 volt, go to step  45 . If .5 volt or less is present, replace HO2S sensor and go to step  47 .
  43. Turn ignition off. Disconnect front HO2S connector. Connect a fused jumper wire between front HO2S harness connector Red wire terminal and negative battery terminal. Using scan tool, perform KOER self-test. See RETRIEVING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. If DTC P1131 or P1151 is present, remove fused jumper wire and go to next step. If DTC P1131 or P1151 is not present, remove fused jumper wire and go to step  47 .
  44. Leave front HO2S disconnected. Measure voltage between front HO2S connector Black/Yellow wire and Red wire terminals. Disconnect a vacuum hose from vacuum tree. Start engine and operate at 2000 RPM. If less than .4 volt within 30 seconds is present, go to next step. If .4 volt or more within 30 seconds is present, replace HO2S and go to step  47 .
  45. Start engine. Ensure engine is at normal operating temperature. Using scan tool, check HO2S PID data. Observe HO2S PID value while wiggling and bending wiring harness between front HO2S and PCM. If PID data voltage stays high (greater than .45 volt) or stays low (less than .45 volt), go to step  47 . If PID data voltage is not as specified, go to next step.
  46. Using an assistant, test drive vehicle under various conditions while observing HO2S PID, trying to simulate original fault (use freeze frame data, if available). If HO2S PID voltage switches properly, go to next step. If voltage does not switch properly, replace HO2S and go to next step.
  47. Reconnect all connections. Turn ignition on. Clear DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. Start engine. Using scan tool, perform OBD II drive mode. See DRIVE MODES  under SELF-DIAGNOSTIC SYSTEM. Using scan tool, access DIAGNOSIS MONITORING TEST RESULTS in GENERIC OBD II FUNCTIONS. Monitor TEST #10:03:81 (front HO2S switching point), #10:01:A1 (left bank voltage amplitude between rich and lean) and #10:01:91 (bank one voltage amplitude between rich and lean). If measured value is within specification, replace PCM and go to next step. See REMOVAL, OVERHAUL & INSTALLATION article. On vehicles equipped with immobilizer system, reprogram ignition key identification numbers. See COMPUTER RELEARN PROCEDURES - IMPORT article in GENERAL INFORMATION. If measured value is not within specification, go to next step.
  48. Perform DTC confirmation procedure. See DTC CONFIRMATION PROCEDURE  under SELF-DIAGNOSTIC SYSTEM. Check for DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. If any other DTC is present, go to appropriate test.
Fig 1: Identifying Powertrain Control Module (PCM) Harness Connector Terminals
G96F31315Courtesy of FORD MOTOR CO.
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