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Home >> Mazda >> 2003 >> Tribute LX, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 61 (Engine Controls - Self-Diagnostics) >> Diagnostic Tests >> DTC P0172: Fuel Trim - Too Rich >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2003 Mazda Protege5 and 2003 Mazda Protege. However, it is still accessible from the selected car via links, so may be relevant.
  1. Verify Related Repair Information Availability -  Turn ignition off. Connect scan tool to DLC-2. Turn ignition on, engine off. Monitor for FREEZE FRAME DATA and ensure data has been recorded. Check service bulletins for repair information related to this DTC. If repair information is not available, go to next step. If repair information is available, perform diagnosis and repair as necessary. After repair, go to next step.
  2. Verify Related Pending Code & Stored DTCs -  Turn ignition off, then start engine. Using scan tool, check for DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. If no other DTCs are present and no driveability problems are present, go to next step. If a driveability problem is present, go to step  9. If any other DTCs are present, go to appropriate DTC trouble shooting procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  3. Identify Trigger DTC For Freeze Frame Data -  Check if DTC P0172 is present in FREEZE FRAME DATA. If DTC P0172 is present, go to next step. If any other DTC is present that triggered freeze frame data, go to appropriate DTC trouble shooting procedure. Refer to DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  4. Verify Current Input Signal Status (Ignition Key To On/Idle) -  Start engine and allow to idle. Using scan tool, access ECT, MAF, TP and VS PIDs. Ensure all PID data is within specification. See PIN VOLTAGE CHARTS . If all PID data is within specification, go to next step. If any PID data is not within specification, diagnose and repair suspect sensor or related wire harness as necessary. See appropriate WIRING DIAGRAM under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS. After repair, go to step  11.
  5. Verify Current Input Signal Status Under Trouble Condition -  Inspect FREEZE FRAME PID data from step  4 while operating vehicle under freeze frame data conditions. If there is no input signal which cause drastic changes, go to next step. If any input signal causes drastic changes, diagnose and repair suspect sensor or related wire harness as necessary. Refer to SYSTEM & COMPONENT TESTING - MAZDA6, MIATA, MPV, PROTEGE & PROTEGE5 article. After repair, go to step  11.
  6. Verify Current Input Signal Status Of Front HO2S -  Using scan tool, access O2S11 PID. O2S11 PID value should be more than .45 volt during acceleration (rich condition) and less than .45 volt during deceleration (lean condition). If PID reading is okay, go to next step. If PID reading is not as specified, replace front HO2S. After repair, go to step  11.
  7. Inspect Fuel Line Pressure -  Turn ignition off. Start engine. Check fuel line pressure with engine running. See FUEL PRESSURE (EXCEPT B2300, B3000, B4000 & TRIBUTE) under FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES article. If line pressure is 30-36 psi (2.1-2.6 kg/cm2 ), go to step  9. If fuel pressure reading is not as specified, go to next step.
  8. Verify Vacuum Is Leading To Pressure Regulator -  Start engine. Disconnect vacuum hose from fuel pressure regulator. If vacuum is present at end of hose, check fuel pump maximum pressure. See FUEL PRESSURE (EXCEPT B2300, B3000, B4000 & TRIBUTE) under FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES article. Also check fuel return hose for clogging. If any problem is found, repair or replace suspected parts. If no problem is found, replace fuel pressure regulator. Repair as necessary. After repair, go to step  11. If no vacuum is present at hose, check vacuum hose routing. If vacuum hoses are okay, replace Pressure Regulator Control (PRC) solenoid valve. Repair as necessary. After repair, go to step  11.
  9. Inspect Purge Solenoid Valve For Whether Stuck Open -  Turn ignition off. Disconnect both hoses from purge solenoid valve. Purge solenoid valve is located at rear of engine compartment. Blow air through purge solenoid valve. If air does not flow through valve, go to next step. If air flows through valve, replace purge solenoid valve. After repair, go to step  11.
  10. Inspect PCV Valve Operation -  Check PCV valve operation. See 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 -  Reconnect all connectors. Turn ignition on, engine off. Clear DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. Perform MODE 1 - PCM ADAPTIVE MEMORY PROCEDURE DRIVE MODE , MODE 2 - EGR SYSTEM REPAIR VERIFICATION DRIVE MODE  and MODE 3 - HO2S, HO2S HEATER & TWC REPAIR VERIFICATION DRIVE MODE  under SELF-DIAGNOSTIC SYSTEM. Check for DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. If DTC P0172 is present, replace PCM. For PCM removal and installation, see POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION article. After repair, go to next step. If same DTC P0172 is not present, go to next step.
  12. Verify After Repair Procedure -  Using scan tool, perform After Repair Procedure. See AFTER REPAIR PROCEDURE . If no other DTCs are present, testing is complete. If any other DTC is present, follow appropriate DTC diagnostic procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
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