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 (see GENERAL TROUBLESHOOTING INFORMATION ).
Poor fuel quality can also cause the DTC P0171/P0174.
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: Mass airflow (MAF) sensor

P0107, P0108, P1128, P1129: Manifold absolute pressure (MAP) sensor

P0133, P0153, P1172, P1174, P2195, P2197, P2237, P2238, P2240, P2241, P2243, P2245, P2247, P2249, P2251, P2252, P2254, P2255, P2A00, P2A03: Air fuel ratio (A/F) sensor (Sensor 1)

P0134, P0135, P0154, P0155: Air fuel ratio (A/F) sensor (Sensor 1) heater

P0137, P0138, P0139, P0157, P0158, P0159, P0141, P0161: Secondary HO2S (Sensor 2) heater

P2646, P2647, P2648, P2649: VTEC system

P0401, P0404, P0406, P2413: Exhaust gas recirculation (EGR) system

P2279: Intake air leakage

Check the fuel pressure (see FUEL PRESSURE TEST ).
Is the fuel pressure OK?

YES -Go to step 2.

NO -
- If the pressure is too high, replace the fuel pressure regulator (see FUEL PRESSURE REGULATOR REPLACEMENT ), then Go to step 2.
- 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.
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.
Check for these conditions:
- Engine coolant temperature (ECT SENSOR 1) above 158°F (70°C)
- Transmission in P or N
- All electrical loads off
Monitor the ENGINE SPEED in the DATA LIST with the HDS. Raise and hold the engine speed steady at 2, 500 ± 100 rpm. While holding the engine speed steady, check the MAF SENSOR in the DATA LIST with the HDS.
Is there about 10.7- 13.1 gm/s?

YES -Replace the injectors (see INJECTOR REPLACEMENT ), then go to step 5.

NO -Replace the MAF sensor/IAT sensor (see MAF SENSOR/IAT SENSOR REPLACEMENT ), then go to step 5.
Turn the ignition switch to ON (II).
Reset the PCM with the HDS.
Do the PCM idle learn procedure (see PCM IDLE LEARN PROCEDURE ).
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.
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 15-55 mph (24-90 km/h) for 15 minutes.
NOTE: DTC P0171, P0172, P0174, and/or P0175 may take up to 40 minutes of test driving to set. Using the HDS, monitor the long term fuel trim (LT FUEL TRIM). If the LT FUEL TRIM stays within 0.8-1.23, there is no problem at this time.
Check for Pending DTCs 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 DTCs or Confirmed DTCs are indicated, Go to the indicated DTC's troubleshooting. ■