DTC Troubleshooting

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.
- 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. P0107, P0108, P1128, P1129: Manifold absolute pressure (MAP) sensor
P0133, P0153, P1172, P1173, P2195, P2197, P2237, P2238, P2240, P2241, P2243, P2245, P2247, P2249, P2251, P2252, P2254, P2255, P2627, P2628, P2630,
P2631, P2AOO, 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

1. Check the fuel pressure.

Is the fuel pressure OK?

YES - Check the valve clearances and adjust them if needed (DTC P0172 and P0175 only).If the valve clearances are OK, replace the injectors, then Go to step 2.

NO - Check these items:
- If the pressure is too high, replace the fuel pressure regulator, then Go to step 2. If the pressure is too low, check the fuel pump, the fuel feed pipe, and the fuel filter. If they are all OK, replace the fuel pressure regulator, then Go to step 2.

2. Turn the ignition switch ON (II).
3. Reset the PCM with the HDS.
4. Do the PCM idle learn procedure.
5. 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.
6. 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 25 - 55 mph(40 - 88 km/h) for 5 minutes, then 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 0.86 - 1.17, there is no problem at this time.

7. Check for Temporary DTCs or DTCs with the HDS.

Is DTC P0171, P0172, P0174, or P0175 indicated?

YES - Check for poor connections or loose terminals at the PCM, then Go to Step 1.

NO - Troubleshooting is complete. If any other Temporary DTCs or DTCs are indicated, Go to the indicated DTC's troubleshooting.