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, P1174, P2195, P2197, P2237,
P2238, P2240, P2241, P2243, P2245, P2247, P2249,
P2251, P2252, P2254, P2255, P2627, P2628, P2630,
P2631, 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

1. Check the fuel pressure.

Is the fuel pressure OK?

YES - If you are troubleshooting DTC P0171 or P0174, go to step 2. If you are troubleshooting DTC P0172 or P0175, check the valve clearances, and adjust if necessary. 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 pressure regulator, the fuel filter, and the fuel lines for restrictions, 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 40 minutes of test driving to set. Use the HDS to monitor the LT FUEL TRIM for 15 minutes of driving under the freeze data conditions. If the value stays within 10 % of 1.0 (0.0%), 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 - Go to step 8.

NO - Troubleshooting is complete. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTCs troubleshooting.

8. Check for poor connections or loose terminals at the PCM.

Are the connections and terminals OK?

YES - Go to step 9.

NO - Repair the connections or terminals, then step 2.

9. Check the fuel quality.

Is the fuel quality OK?

YES - Replace the injectors, then go to step 2.

NO - Drain the fuel tank, replace the fuel, then go to step 2.