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
- Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information (see GENERAL TROUBLESHOOTING INFORMATION ).
- 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 air flow (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, P2270, P2271, P2272, P2273: Secondary HO2S (Sensor 2)
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 7.
- If the pressure is too low, check the fuel pump, the fuel feed pipe and the fuel filter. If they are OK, replace the fuel pressure regulator (see FUEL PRESSURE REGULATOR REPLACEMENT ), then go to step 7.
- 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 7.
- Start the engine. Hold the engine speed at 3,000 rpm without load (in Park or neutral) until the radiator fan comes on, then let it idle.
- Check for these conditions:
- Engine coolant temperature (ECT SENSOR 1) above 176°F (80°C)
- Transmission in Park or neutral
- All electrical loads off
- 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 5.
NO - Go to step 6.
- While holding the engine speed at 2,500 rpm, check the MAF SENSOR in the DATA LIST with the HDS.
Is there about 9.8- 11.9 gm/s?
YES - Check the engine valve clearances and adjust if necessary (see VALVE CLEARANCE ADJUSTMENT ). If the valve clearances are OK, replace the injectors (see INJECTOR REPLACEMENT ), then go to step 7.
NO - Replace the MAF sensor/IAT sensor (see MAF SENSOR/IAT SENSOR REPLACEMENT ), then go to step 7.
- Turn the ignition switch 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 Park or neutral) 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 position
- 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 long term fuel trim (LT FUEL TRIM) or the air fuel feed back average (AF FB AVE). If the long term fuel trim/air fuel feed back average stays within 0.84-1.18, there is no problem at this time. - Check for Temporary DTCs or 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 Temporary DTCs or DTCs are indicated, go to the indicated DTCs troubleshooting.