DTC P0172, P0175 [AJ]

BME010200100222

DTC P0172

DTC P0175

Fuel trim system (RH) too rich

Fuel trim system (LH) too rich

DETECTION CONDITION

• PCM monitors short fuel trim (SHRTFT) and long fuel trim (LONGFT) values when closed loop fuel control. If fuel trim exceeds preprogrammed criteria, PCM determines that the fuel system is too rich.
Diagnostic support note
• This is a continuous monitor. (FUEL SYSTEM)
• MIL illuminates if PCM detects the above malfunction conditions in two consecutive drive cycles.
• PENDING CODE is available if PCM detects the above malfunction condition during first drive cycle.
• 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

1
VERIFY FREEZE FRAME DATA HAS BEEN RECORDED
• Has FREEZE FRAME DATA been recorded?
Yes
Go to the next step.
No
Record FREEZE FRAME DATA on repair order, then go to the 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 the next step.
No
Go to the next step.
3
VERIFY RELATED PENDING CODE OR STORED DTCS
• Turn the ignition switch off, then to the ON position (Engine off).
• Verify related PENDING CODE or stored DTCs.
• Is other DTCs present?
Yes
Go to the applicable DTC inspection.
No
If driveability concern is present, go to Step 9.
If not, go to the next step.
4
IDENTIFY TRIGGER DTC FOR FREEZE FRAME DATA
• Is DTC P0172 or P0175 on FREEZE FRAME DATA?
Yes
Go to the next step.
No
Go to troubleshooting procedures for DTC on FREEZE FRAME DATA.
5
VERIFY CURRENT INPUT SIGNAL STATUS (IGNITION SWITCH TO ON/IDLE)
• Access ECT, MAF, TP and VSS PIDs using the WDS or equivalent.
• Is there any signal that is far out of specification when the ignition switch is at the ON position and the engine runs?
Yes
Inspect the sensor and excessive resistance in related wiring harnesses. Repair or replace if necessary. Then go to Step 11.
No
Go to the next step.
6
VERIFY CURRENT INPUT SIGNAL STATUS UNDER TROUBLE CONDITION
• Inspect PID data while simulating FREEZE FRAME DATA condition.
• Is there any input signal which causes drastic changes?
Yes
Inspect the sensor and related wiring harnesses, and repair or replace it. Then go to Step 11.
No
Go to the next step.
7
VERIFY CURRENT INPUT SIGNAL STATUS OF Front HO2S
• Access O2S11 for P0172 or O2S21 for P0175 PID using WDS or equivalent.
• Verify PID while racing engine (in PARK or NEUTRAL).
• Is PID reading normal?

- Above 0.45 V when suddenly depress the accelerator pedal (rich condition).

- Below 0.45 V just after release of the accelerator pedal (lean condition)

Yes
Go to the next step.
No
Replace the front HO2S.
Then go to Step 11.
8
INSPECT FUEL LINE PRESSURE
• Turn the ignition switch off.
• Connect fuel gauge on the fuel pipe.
• Start the engine and run it at idle.
• Inspect fuel line pressure.
• Is fuel line pressure normal?
Yes
Go to the next step.
No
Inspect fuel pump maximum pressure and Fuel return line for clogged.
• If any problem found, repair or replace the parts.
• If all items above are normal, replace the pressure regulator.
Then go to Step 11.
9
INSPECT LONG TERM FUEL TRIM
• Turn the ignition switch off.
• Disconnect purge hose from intake manifold and plug opening end of hose and intake manifold.
• Access following PIDs
- For P0172: LONGFT1
- For P0175: LONGFT2
• Does it shift to positive value?
Yes
Inspect the purge solenoid valve.
Repair or replace it if necessary, then go to Step 11.
No
Go to the next step.
10
INSPECT PCV VALVE OPERATION
• Inspect the PCV valve operation.
• Is the PCV valve normal?
Yes
Go to the next step.
No
Replace the PCV valve, then go to the next step.
11
VERIFY TROUBLESHOOTING OF DTC P0172 or P0175 COMPLETED
• Make sure to reconnect all disconnected connectors.
• Turn the ignition switch to the ON position (Engine off).
• Clear the DTC from the PCM memory using the WDS or equivalent.
• Run PCM adaptive memory procedure drive mode and HO2S heater, HO2S, and TWC repair verification drive mode. (European (L.H.D.) specs.)
• Run PCM adaptive memory procedure drive mode and HO2S heater, HO2S, and EGR system repair verification drive mode. (Australian, General (L.H.D. R.H.D.) specs.)
• Stop the vehicle and access PID/DATA MONITOR RECORDED to inspect DRIVE MODE completion status.
• Verify RFCFLAG changes to OFF for FUEL SYSTEM MONITOR. If not, run DRIVE MODE again.
• Access PENDING CODE.
• Is the PENDING CODE of same DTC present?
Yes
Replace the PCM, then go to the next step.
No
Go to the next step.
12
VERIFY AFTER REPAIR PROCEDURE
• Perform "After Repair Procedure".
• Is there any DTC present?
Yes
Go to the applicable DTC inspection.
No
Troubleshooting completed.