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Home >> Mazda >> 2013 >> 5 Grand Touring >> Repair and Diagnosis >> External Pages >> Different car >> Section 58 (Engine Controls [Self-Diagnostics 2.3L]) >> Diagnostic Tests >> DTC P0172: Fuel Trim System - Too Rich >> 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 related PENDING CODE or stored DTCs. If no other DTCs are present and a driveability concern is not present, go to next step. If no other DTCs are present and a driveability concern is present, go to step  9. If any other DTC is present, go to appropriate DTC trouble shooting procedure. Refer to DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  4. Identify Trigger DTC For FREEZE FRAME DATA -  If DTC P0172 is present on FREEZE FRAME DATA, go to next step. If any other DTC triggered FREEZE FRAME DATA, diagnose that DTC first. Refer to DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  5. Verify Current Input Signal Status (Ignition Key To On/Idle) -  Access APP, APP1, APP2, ECT, MAF, TP and VSS PIDs using WDS or equivalent. If any input signal is far out of specification when ignition is on and engine runs, check suspected sensor and for excessive resistance in related wiring harnesses. Repair or replace if necessary. After repair, go to step  11. If all input signals are within specification when ignition is on and engine runs, go to next step.
  6. Verify Current Input Signal Status Under Trouble Condition -  Check PID data 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 suspected sensor and related wiring harnesses. Repair or replace if necessary. After repair, go to step  11.
  7. Verify Current Input Signal Status -  Warm up engine. Access O2S11 PID using WDS or equivalent. Check PID under following accelerator pedal conditions (in PARK - ATX or NEUTRAL - MTX).
    • More Than 0.55 volt  when suddenly depressing accelerator pedal (rich condition)
    • Less Than 0.55 volt  just after release of accelerator pedal (lean condition)
    If PID readings are okay, go to next step. If PID readings are not okay, replace suspected front HO2S. After repair, go to step  11.
  8. 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 okay, go to next step. If fuel line pressure is not okay, replace fuel pump. After repair, go to step  11.
  9. Inspect Long Term Fuel Trim -  Turn ignition off. Disconnect purge hose from intake manifold and plug open end of hose and intake manifold. Access LONGFT1 PID. If LONGFT1 PID does not change to positive value, go to next step. If LONGFT1 PID value shifts to positive value, check purge solenoid valve. PURGE SOLENOID VALVE under RELAYS & SOLENOIDS in SYSTEM & COMPONENT TESTING - MAZDA6, MIATA, MPV, PROTEGE & PROTEGE5 article. Repair or replace purge solenoid valve if necessary. After repair, go to step  11.
  10. Inspect PCV Valve Operation -  Inspect PCV valve operation. Refer to POSITIVE CRANKCASE VENTILATION under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - MAZDA6, MIATA, MPV, PROTEGE & PROTEGE5 article. If PCV valve is okay, go to next step. If PCV valve is faulty, replace PCV valve. After repair, go to next step.
  11. Verify Trouble Shooting Of DTC P0172 Completed -  Make sure to reconnect all disconnected connectors. Turn ignition on, engine off. Clear DTC from PCM memory using WDS or equivalent. Perform MODE 1 - PCM ADAPTIVE MEMORY PRODUCE DRIVE MODE  and MODE 3 - HO2S HEATER, HO2S & TWC REPAIR VERIFICATION DRIVE MODE  under DRIVE CYCLES. Stop vehicle and access ON BOARD READINESS TEST to inspect DRIVE MODE completion status. Verify FUEL_EVAL PID changes to YES. If not, run MODE 3 - HO2S HEATER, HO2S & TWC REPAIR VERIFICATION DRIVE MODE  under DRIVE CYCLES 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.
  12. 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.
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