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Home >> Mazda >> 2003 >> Tribute LX, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 26 (Engine Controls - Self-Diagnostics) >> Diagnostic Tests >> DTC P0172: Fuel Trim, Too Rich >> Diagnosis & Repair Procedure

Diagnosis & Repair Procedure

WARNING: This page is about a different car, the 2002 Mazda Protege5 and 2002 Mazda Protege. However, it is still accessible from the selected car via links, so may be relevant.
  1. 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 step  11.
  2. Turn ignition switch off and 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 or rough idle are present, go to next step. If a driveability problem is present, go to step  9. If DTCs are present, go to appropriate test.
  3. Check if DTC P0172 is present in FREEZE FRAME DATA. If DTC is present, go to next step. If DTC is not present, problem is intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article.
  4. Start engine and allow to idle. Using scan tool, access PID data for ECT, MAF, TP and VS. Ensure all PID data is within specification. See PIN VOLTAGE/PID VALUE CHARTS article. If all PID data is within specification, go to next step. If any PID data is not within specification, diagnose and repair as necessary and go to step  11.
  5. Referring to FREEZE FRAME DATA, operate vehicle under same conditions as when DTC was set. Record PID data for ECT, MAF, TP and VS. If all PID data is within specification, go to next step. If any PID data is not within specification, go to applicable test in SYSTEM & COMPONENT TESTING - MIATA, MILLENIA, MPV, PROTEGE, PROTEGE5 & 626 article. Diagnose and repair as necessary and go to step  11.
  6. Using scan tool, access O2S11 PID data. Depress accelerator pedal to Wide Open Throttle (WOT) and release to race engine. Scan tool should display O2S11 PID is more than .45 volt during acceleration (rich condition) and less than .45 volt during deceleration fuel cut (lean condition). If PID voltage is as specified, go to next step. If PID voltage is not as specified, replace front HO2S and go to step  11.
  7. Turn ignition switch off. Start engine. Check fuel line pressure. 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. Start engine. Disconnect vacuum hose from fuel pressure regulator. If vacuum is present at hose, check fuel pump maximum pressure. See FUEL PRESSURE (EXCEPT B2300, B3000, B4000 & TRIBUTE) under FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES article. Repair as necessary. Check fuel return hose for plugging or restriction. Repair as necessary. If no problem is found, replace fuel pressure regulator and go to step  11. If no vacuum is present at hose, check hose routing. If hoses are okay, replace PRC solenoid valve and go to step  11. If hoses are misrouted, repair as necessary and go to step  11.
  9. Turn ignition switch 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 and go to step  11.
  10. Check PCV valve operation. See EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - MIATA, MILLENIA, MPV, PROTEGE, PROTEGE5 & 626 article. Replace as necessary and go to next step. If PCV valve is okay, go to next step.
  11. Reconnect all connectors. Turn ignition switch on. Clear DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. Perform DRIVE MODE 1 - PCM ADAPTIVE MEMORY , DRIVE MODE 2 - EGR MONITOR REPAIR VERIFICATION  and DRIVE MODE 3 - HO2S, HO2S HEATER & TWC REPAIR VERIFICATION  under SELF-DIAGNOSTIC SYSTEM. Check for DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. If DTC P0172 is present, replace PCM and go to next step. If DTC P0172 is not present, go to next step.
  12. Cycle ignition switch from off to on. Check for DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. If no other DTCs are present, testing is complete. If any other DTC is present, go to applicable test and repair.
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