DTC Troubleshooting

DTC Troubleshooting: 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.
- If some 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, P2272: 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 -

- If the pressure is too high, replace the fuel pressure regulator Service and Repair, then go to step 6.
- If the pressure is too low, check for restrictions in the fuel pump, the fuel pressure regulator, the fuel filter, and the fuel lines. If they are OK, replace the fuel pressure regulator Service and Repair, then go to step 6.

2. Check for vacuum leaks at these parts:

- PCV valve
- PCV hose
- EVAP canister purge valve
- Throttle body
- Intake manifold
- Brake booster
- Brake booster hose
- Air intake duct

Are the parts OK?

YES -

Go to step 3.

NO -

Repair or replace parts with leaks, then go to step 6.

3. Start the engine. Hold the engine speed at 3,000 rpm without load (in P or N) until the radiator fan comes on, then let it idle.

4. Check for these conditions:

- Engine coolant temperature (ECT SENSOR 1) above 176 °F (80 °C)
- Transmission in P or N
- All electrical loads off

5. Monitor the ENGINE SPEED in the DATA LIST with the HDS. Raise and hold the engine speed steady at 2,500 rpm. While holding the rpm steady, check the MAF SENSOR in the DATA LIST.

Is there about 9.0-12.7 gm/s?

YES -

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 PCM with the HDS.

8. Do the PCM idle learn procedure PCM Idle Learn Procedure.

9. Start the engine. Hold the engine speed at 3,000 rpm without load (in P or N) 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)
- Transmission in D
- 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 average 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 and recheck.

NO -

Troubleshooting is complete. If any other Pending or Confirmed DTCs are indicated, go to the indicated DTC's troubleshooting.�