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DTC P0172 [L3]

BME010200100W21

DTC P0172 | Fuel trim system too rich
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DETECTION CONDITION | • PCM monitors short fuel trim (SHRTFT) and long fuel trim (LONGFT) values during OBD DRIVE MODE operation. If fuel trim exceeds preprogrammed criteria, PCM determines that fuel system is too rich. Diagnostic support note • This is a continuous monitor. (FUEL SYSTEM)
• MIL illuminates if PCM detects the above malfunction condition in two consecutive drive cycles or in one drive cycle while the DTC for the same malfunction has been stored in the PCM.
• PENDING CODE is available if PCM detects the above malfunction condition.
• FREEZE FRAME DATA is available.
• DTC is stored in the PCM memory.
POSSIBLE CAUSE | • Misfire • Front HO2S deterioration • Front HO2S heater malfunction • Pressure regulator malfunction • Fuel pump malfunction
• Fuel return hose clogged
• Purge solenoid valve malfunction
• Purge solenoid hoses improper connection
• PCV valve malfunction

Diagnostic procedure

STEP | INSPECTION | ACTION
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1 | VERIFY FREEZE FRAME DATA HAS BEEN RECORDED • Has FREEZE FRAME DATA been recorded? | Yes | Go to next step.
No | Record FREEZE FRAME DATA on repair order, then go to next step.
2 | VERIFY RELATED SERVICE INFORMATION AVAILABILITY • Check for related Service Information availability. • Is any related Service Information available? | Yes | Perform repair or diagnosis according to available Service Information. • If vehicle is not repaired, go to next step.
No | Go to next step.
3 | VERIFY RELATED PENDING CODE OR STORED DTCS • Turn ignition key to OFF, then ON (Engine OFF). • Verify related pending code or stored DTCs. • Is other DTCs present? | Yes | Go to appropriate DTC troubleshooting procedures.
No | If driveability concern or rough idle is present, go to Step 9. If not, go to next step.
4 | IDENTIFY TRIGGER DTC FOR FREEZE FRAME DATA • Is DTC P0172 on FREEZE FRAME DATA? | Yes | Go to next step.
No | Go to troubleshooting procedures for DTC on FREEZE FRAME DATA.
5 | VERIFY CURRENT INPUT SIGNAL STATUS (IGNITION KEY TO ON/IDLE) • Access ECT, MAF, TP and VSS PIDs using WDS or equivalent. • Is there any signal that is far out of specification when ignition key is at ON and engine is running? | Yes | Inspect suspected sensor and excessive resistance in related wiring harnesses. Repair or replace if necessary. Then go to Step 11.
No | Go to next step.
6 | VERIFY CURRENT INPUT SIGNAL STATUS UNDER TROUBLE CONDITION • Inspect same PIDs as is Step 4 while simulating FREEZE FRAME DATA condition. • Is there any input signal which causes drastic changes? | Yes | Inspect suspected sensor and related wiring harnesses, and repair or replace it. Then go to Step 11.
No | Go to next step.
7 | VERIFY CURRENT INPUT SIGNAL STATUS OF FRONT HO2S • Access O2S11 PID using WDS or equivalent. • Verify PID while racing engine (in NEUTRAL). • Is PID reading okay? - Above 0.55 V when accelerator pedal is suddenly depressed (rich condition).

- Below 0.55 V just after release of accelerator pedal (lean condition)

Yes
Go to next step.
No | Replace suspected front HO2S. Then go to Step 11.
8 | INSPECT FUEL LINE PRESSURE • Turn ignition key to OFF. • Connect fuel gauge to fuel pipe. • Start engine and run it at idle. • Inspect fuel line pressure while engine running.
(See FUEL LINE PRESSURE INSPECTION [L3].)
• Is fuel line pressure okay?
Yes
Go to next step.
No | Replace fuel pump unit, then go to Step 11
9 | INSPECT PURGE SOLENOID VALVE FOR STUCK OPEN • Turn ignition key to OFF. • Disconnect both hoses from purge solenoid valve. • Blow air through purge solenoid valve. • Does air blow through? | Yes | Replace purge solenoid valve. Then go to Step 11.
No | Go to next step.
10 | INSPECT PCV VALVE OPERATION • Inspect PCV valve operation. (See PCV VALVE INSPECTION [L3].) • Is PCV valve okay? | Yes | Go to next step.
No | Replace PCV valve, then go to next step.
11 | VERIFY TROUBLESHOOTING OF DTC P0172 COMPLETED • Make sure to reconnect all disconnected connectors. • Turn ignition key to ON (Engine OFF). • Clear DTC from memory using WDS or equivalent. • Run OBD DRIVE MODE.
(See OBD DRIVE MODE [L3].)
• Is PENDING CODE of same DTC present?
Yes
Replace PCM, then go to next step.
(See PCM REMOVAL/INSTALLATION [L3].)
No | Go to next step.
12 | VERIFY AFTER REPAIR PROCEDURE • Perform "After Repair Procedure". (See AFTER REPAIR PROCEDURE [L3].) • Is there any DTC present? | Yes | Go to applicable DTC troubleshooting. (See DTC TABLE [L3].)
No | Troubleshooting completed.