LEMON Manuals: Even more car manuals for everyone
Home >> Mazda >> 2002 >> Tribute LX, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 61 (Engine Controls [Self-Diagnostics 3.0L]) >> Diagnostic Tests >> DTC P0171 Or DTC P0174 >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2003 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.
  1. If FREEZE FRAME DATA has been recorded, go to next step. If FREEZE FRAME DATA has not been recorded, record FREEZE FRAME DATA. Go to next step.
  2. Verify Related Repair Information Availability -  Check for related Service Bulletins and/or on-line repair information availability. If any related repair information is available, perform repair or diagnosis according to available repair information. If vehicle is not repaired, go to next step. If related repair information is not available, go to next step.
  3. Verify Related Pending Code Or Stored DTCs -  Turn ignition off, then on (engine off). Verify pending code or stored DTCs using WDS or equivalent. If any other DTC is present, go to appropriate DTC trouble shooting procedure. Refer to DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no other DTCs are present, go to next step.
  4. 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 triggered FREEZE FRAME DATA, go to appropriate DTC trouble shooting procedure for DTC that triggered FREEZE FRAME DATA. Refer to DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  5. Verify Current Input Signal Status (Ignition On/Engine Idle) -  Access APP1, APP2, ECT, MAF, TP_REL and VSS PIDs using WDS or equivalent. If no signal is far out of specification when ignition is on and engine running, go to next step. If any signal is far out of specification when ignition is on and engine running, check for faulty sensor and excessive resistance in related wiring harness. Repair or replace if necessary. After repair, go to step  16.
  6. Verify Current Input Signal Status Under Trouble Condition -  Inspect same PIDs as in step  5 while simulating FREEZE FRAME DATA condition. If no input signal causes drastic changes, go to next step. If any input signal causes drastic changes, check for faulty sensor and related wiring harness. Repair or replace if necessary. After repair, go to step  16.
  7. Verify Current Input Signal Status Of Right & Left Front HO2S -  Access O2S11 for P0171 or O2S21 for P0174 PID using WDS or equivalent. Check PID under following accelerator pedal condition in Park (ATX) or Neutral (MTX).
    • Rich Condition -  0.45 volt or more when the accelerator pedal is suddenly depressed
    • Lean Condition -  0.45 volt or less just after release of accelerator pedal
    If PID reading is okay, check for air suction at following locations due to cracks, damage or loose parts:
    • From air cleaner to throttle body
    • From throttle body to dynamic chamber
    • From dynamic chamber to intake manifold
    • Vacuum hoses
    Repair or replace any faulty part. After repair, go to step  16. If PID reading is not as specified, visually inspect for any gas leakage between exhaust manifold and right or left front HO2S. If there is no leakage, replace right or left front HO2S. If leakage is present, tighten right or left front HO2S. After repair, go to step  16.
  8. Inspect MAF PID -  Start engine. Access MAF PID using WDS or equivalent. Verify that MAF PID reading changes quickly according to RPM when racing engine. If MAF PID response is okay, go to next step. If MAF PID response is not okay, replace MAF/IAT sensor. After repair, go to step  16.
  9. Inspect For Excessive Air Suction Of Intake Air System -  Visually inspect for loose, cracked or damage hoses on intake air system. If no malfunction is present, go to next step. If any malfunction is present, repair or replace source of air suction. After repair, go to step  16.
    10. NOTE: During following procedure, if engine will not start, inspect fuel line pressure with ignition on.
  10. Inspect Fuel Line Pressure -  Turn ignition off. Inspect fuel line pressure while engine is running. Refer to FUEL PRESSURE (EXCEPT B2300, B3000, B4000 & TRIBUTE) under FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES article. If fuel line pressure is too low, go to next step. If fuel line pressure okay, go to step  13. If fuel line pressure is excessively high, replace fuel pump unit. Refer to FUEL PUMP under FUEL SYSTEM in REMOVAL & INSTALLATION article. After repair, go to step  16.
  11. Inspect Fuel Line From Fuel Pump To Fuel Delivery Pipe -  Visually inspect fuel line for any leakage. If no fuel leakage is found, inspect low-pressure side fuel filter for foreign material or stain inside fuel filter. If foreign material or stain is found inside low-pressure fuel filter, clean fuel tank and filter. If okay, replace fuel pump unit. Refer to FUEL PUMP under FUEL SYSTEM in REMOVAL & INSTALLATION article. After repair, go to step  16. If any fuel leakage is found, replace suspected fuel line. After repair, go to step  16.
  12. Inspect Fuel Injector Operation -  Remove fuel injector from suspected bank. Swap injector with injector on the other bank. Start engine. If there is no DTC for fuel trim system lean for bank which fuel injector was switched to, go to next step. If there is a DTC for fuel trim system lean for bank which has a suspected fuel injector, replace faulty fuel injector. Refer to FUEL RAILS & INJECTORS under FUEL SYSTEM in REMOVAL & INSTALLATION article. After repair, go to step  16.
  13. Inspect Ignition System Operation -  Perform Spark Test. Refer to SPARK TEST  under SYSTEM TESTS. If result of Spark Test is okay, go to next step. If result of Spark Test is not okay, repair or replace malfunctioning part according to spark test results. After repair, go to step  16.
  14. Inspect Variable Valve Timing Control System Operation -  Inspect Variable Valve Timing Control System Operation. Refer to VARIABLE VALVE TIMING CONTROL SYSTEM OPERATION INSPECTION  under SYSTEM TESTS. If variable valve timing control system works properly, go to next step. If variable valve timing control system does not work properly, repair or replace malfunctioning part according to Variable Valve Timing Control System Inspection results. After repair, go to step  16.
  15. Inspect Engine Compression -  Inspect engine compression. Refer to MECHANICAL INSPECTION in BASIC DIAGNOSTIC PROCEDURES article. If engine compression is okay, go to next step. If engine compression is not okay, perform engine overhaul for repairs. After repair, go to next step.
  16. Verify Trouble Shooting Of DTCs P0171 Or P0174 Is Completed -  Make sure to reconnect all disconnected connectors. Clear DTC from memory using WDS or equivalent. See CLEARING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. Run MODE 1 - PCM ADAPTIVE MEMORY PRODUCE DRIVE MODE , MODE 2 - EGR SYSTEM REPAIR VERIFICATION DRIVE MODE  and MODE 3 - HO2S HEATER, HO2S & TWC REPAIR VERIFICATION DRIVE MODE  . Stop vehicle and access ON BOARD READINESS TEST to inspect DRIVE MODE completion status. Verify FUEL_EVAL PID changes to YES. If not, run DRIVE MODE again. Access PENDING CODE. If PENDING CODE of same DTC is not present, go to next step. If PENDING CODE of same DTC is present, replace PCM. For PCM removal and installation, see POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL & INSTALLATION article. After repair, go to next step.
  17. Verify After Repair Procedure -  Using scan tool, perform After Repair Procedure. See AFTER REPAIR PROCEDURE . If any DTCs are present, go to appropriate DTC inspection. Refer to DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are present, trouble shooting is complete.
scientia non olet · About LEMON Manuals