DTC Troubleshooting
DTC Troubleshooting: P0171, P0172, P0174, P0175, P0171, P0172, P0174, P0175
DTC P0171:
Rear Bank (Bank 1) Fuel System Too Lean
DTC P0172:
Rear Bank (Bank 1) Fuel System Too Rich
DTC P0174:
Front Bank (Bank 2) Fuel System Too Lean
DTC P0175:
Front Bank (Bank 2) Fuel System Too Rich
NOTE:
- Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information Initial Inspection and Diagnostic Overview.
- Poor fuel quality can also cause DTC P0171/P0174.
- If any of the DTCs listed below are stored at the same time as DTC P0171, P0172, P0174, and/or P0175, troubleshoot those DTCs first, then recheck for P0171, P0172, P0174, and/or P0175:
P0101, P0102, P0103: MAF sensor
P0107, P0108, P1128, P1129: MAP sensor
P0133, P0153, P1172, P1174, P2195, P2197, P2237, P2238, P2240, P2241, P2243, P2245, P2247, P2249, P2251, P2252, P2254, P2255, P2A00, P2A03: A/F sensor (Sensor 1)
P0134, P0135, P0154, P0155: A/F sensor (Sensor 1) heater
P0137, P0138, P0139, P0157, P0158,P0159, P2270, P2271, P2272, P2273: Secondary HO2S (Sensor 2)
P0141, P0161: Secondary HO2S (Sensor 2) heater
P0401, P0404, P0406, P2413: EGR system
P2279: Intake air leakage
P2646, P2647, P2648, P2649: VTEC system
1. Check the fuel pressure Testing and Inspection.
Is the fuel pressure OK?
YES -
Go to step 2.
NO -
Check these items:
- If the pressure is too high, replace the fuel pressure regulator; without SH-AWD, with SH-AWD Service and Repair, then go to step 6.
- If the pressure is too low, check the fuel pump, the fuel pressure regulator, the fuel filter, and the fuel lines for restrictions, then go to step 6.
2. Start the engine. Hold the engine speed at 3,000 rpm without load (A/T in P or N, M/T in neutral) until the radiator fan comes on, then let it idle.
3. Check for these conditions:
- Engine coolant temperature (ECT SENSOR 1) above 158 °F (70 °C)
- A/T in P or N, M/T in neutral
- All electrical loads off
4. Monitor the ENGINE SPEED in the DATA LIST with the HDS, and hold the engine speed at 2,500 rpm. Once the engine speed is met, hold the accelerator pedal steady for more than 10 seconds.
Did the engine speed vary more than 100 rpm from 2,500 rpm?
YES -
Repeat step 4.
NO -
Go to step 5.
5. While holding the engine speed at 2,500 rpm, check the MAF SENSOR in the DATA LIST with the HDS.
Is there about 11.0-15.5 gm/s (J35Z6 engine) or 11.8-16.6 gm/s (J37A4 engine)?
YES -
Check the engine valve clearances, and adjust them if needed. If the valve clearances are OK, replace the injectors Service and Repair, then go to step 6.
NO -
Replace the MAF sensor/IAT sensor Service and Repair, then go to step 6.
6. Turn the ignition switch to ON (II), or press the engine start/stop button to select the ON mode.
7. Reset the ECM/PCM with the HDS.
8. Do the ECM/PCM idle learn procedure ECM/PCM Idle Learn Procedure.
9. Start the engine. Hold the engine speed at 3,000 rpm without load (A/T in P or N, M/T in neutral) until the radiator fan comes on, then let it idle.
10. Test-drive under these conditions:
- Engine coolant temperature (ECT SENSOR 1) above 158 °F (70 °C)
- A/T in D, M/T in 4th
- Drive at a steady speed between 15-75 mph (24-120 km/h) for 15 minutes.
NOTE: DTC P0171, P0172, P0174, and/or P0175 may take up to 80 minutes of test driving to set. Using the HDS, monitor the short term fuel trim (ST FUEL TRIM). If the ST FUEL TRIM stays within 0.8-1.21, there is no problem at this time.
11. Check for Pending or Confirmed DTCs with the HDS.
Is DTC P0171, P0172, P0174, or P0175 indicated?
YES -
Go to step 1.
NO -
Troubleshooting is complete. If any other Pending or Confirmed DTCs are indicated, go to the indicated DTC's troubleshooting.�