LEMON Manuals: Even more car manuals for everyone
Home >> Mazda >> 2002 >> Tribute LX, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 69 (Engine Controls - Self-Diagnostics) >> Diagnostic Tests >> DTC P0171 Or DTC P0174 >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2003 Mazda Tribute. However, it is still accessible from the selected car via links, so may be relevant.
  1. If QUICK TEST was not performed, go to QUICK TEST  under SELF-DIAGNOSTIC SYSTEM. If QUICK TEST was performed and misfire DTCs (P0300-P0306) were received during Continuous Memory Testing or driveability concern is present, go to step  6. If Continuous Memory DTCs were not present, go to next step. If any other DTC is present, go to appropriate DTC inspection. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  2. Identify Trigger DTC For FREEZE FRAME DATA -  If DTC P0171 or P0174 are on FREEZE FRAME DATA, go to next step. If DTC P0171 or P0174 are not on FREEZE FRAME DATA, go to trouble shooting procedure for DTC that triggered FREEZE FRAME DATA.
  3. Verify Current Input Signal Status -  Start engine. Access ECT V, MAF/IAT V, TP V and VSS PIDs using scan tool. If there is any signal that is far out of specification during KOER, check suspect sensor for excessive resistance in related harnesses. Repair as necessary. See appropriate WIRING DIAGRAM under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS. After repair, go to step  14. If no sensor signals are out of specification, go to next step.
  4. Verify Current Input Signal Status Under Trouble Condition -  Access ECT V, MAF/IAT V, TP V and VSS PIDs while simulating FREEZE FRAME DATA condition. If there is any input signal which causes drastic changes, check suspect sensor and related wiring harness. Repair or replace as necessary. After repair, go to step  14. If there are no input signals which cause drastic changes, go to next step.
  5. Verify Current Input Signal Status Of Front HO2S (RH, LH) -  Access O2S11 PID for P0171 or O2S21 PID for P0174. Check PID under following accelerator pedal condition (in Park):
    • Sudden depress of accelerator pedal (rich condition) should read more than 0.45 volt.
    • Sudden release of accelerator pedal (lean condition) should read less than 0.45 volt.

    If PID is reading correctly, check for air leaks at following areas due to cracks, damaged and loose parts:

    • From air cleaner to throttle body.
    • From throttle body to dynamic chamber.
    • From dynamic chamber to intake manifold.
    • Vacuum hoses.
    Engine speed may change when rust penetrating agent is sprayed on the air suction area. Repair or replace any faulty part. After repair, go to step  14. Visually inspect for any exhaust leakage between exhaust manifold and H20S. If there is no leakage, replace HO2S. After repair, go to step  14.

  6. Inspect MAF/IAT V PID -  Start engine. Access MAF/IAT V PID using scan tool. Race engine. Ensure that MAF/IAT V PID changes quickly according to racing engine RPM. If MAF/IAT V PID response is okay, go to next step. If MAF/IAT V PID response is not okay, replace MAF/IAT sensor. After repair, go to step  14.
  7. Inspect For Excessive Air Suction Of Intake Air System -  Visually inspect air intake system for cracks, damage, or loose parts. If no problem is found, go to next step. If problem is found, repair source of air leak. After repair, go to step  14.
  8. Inspect Fuel Line Pressure -  Turn ignition off. Connect fuel pressure gauge. Start engine. If fuel pressure reading is 55-70 psi (380-482 kPa), go to step  12. If fuel pressure is not as specified, go to next step.
  9. Inspect Fuel Pump Circuit -  Turn ignition off. Check fuel pump circuit for open or poor connection. See appropriate WIRING DIAGRAM under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS. If circuit is okay, go to next step. If fuel pump circuit is not okay, repair suspect circuit as necessary. After repair, go to step  14.
  10. Inspect Fuel Line From Fuel Pump To Fuel Delivery Line -  Visually inspect fuel line for any leakage. If no fuel leaks are found, go to next step. If any fuel leakage is found, replace fuel line. After repair, go to step  14.
  11. Inspect Fuel Filter -  Inspect fuel filter for:
    • Restriction or clogging at high pressure side.
    • Foreign material or stains at low pressure side.
    If any condition or fault is found on high pressure side, replace fuel filter. If problem is found on low pressure side, clean fuel tank and low pressure filter. After repair, go to step  14. If no condition or fault is found, replace fuel pump. After repair, go to step  14.
  12. Inspect Engine Compression -  Perform an Engine Compression test. Refer to MECHANICAL INSPECTION under PRELIMINARY INSPECTION & ADJUSTMENTS in BASIC DIAGNOSTIC PROCEDURES article. If compression readings are okay, go to next step. If engine compression is not okay, overhaul engine.
  13. Inspect Fuel Injector Operation -  Remove injector from suspected bank and swap with injector from other bank. Start engine. Using scan tool, monitor FREEZE FRAME DATA. If fuel trim system is not lean for bank which has suspected injector, go to next step. If fuel trim system is lean for bank which has suspected injector, turn ignition off. Replace fuel injector. After repair, go to next step.
  14. Drive Cycle -  Reconnect all disconnected connectors. Clear DTCs from PCM memory using scan tool. Perform FUEL OR MISFIRE MONITOR REPAIR VERIFICATION DRIVE CYCLE  or HO2S MONITOR REPAIR VERIFICATION DRIVE CYCLE  under MONITOR REPAIR VERIFICATION DRIVE CYCLES. If same DTC is present, replace faulty PCM. If same DTC is not present, go to next step.
  15. Verify Trouble Shooting Of DTCs Completed -  Perform QUICK TEST  under SELF-DIAGNOSTIC SYSTEM. If any DTC is present, go to applicable procedure for other DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are set, trouble shooting is complete.
scientia non olet · About LEMON Manuals