P0171

DTC P0171: Fuel System Too Lean

NOTE: If some of the DTCs listed below are stored at the same time as DTC P0171 and/or P0172, troubleshoot those DTCs first, then recheck for P0171 and/or P0172.

P0107, P0108, P1128, P1129: MAP Sensor
P0135: Primary HO2S (Sensor 1) Heater
P0137, P0138: Secondary HO2S (Sensor 2)
P0141: Secondary HO2S (Sensor 2) Heater
P0401: EGR Flow Insufficient
P1259: VTEC System
P1491: EGR valve Position Insufficient
P1498: EGR valve Position sensor High voltage

1. Check the fuel pressure.

Is fuel pressure OK?

YES - Go to step 2.

NO - Check these items:
- If the pressure is too high, check the fuel pressure regulator, and the fuel return pipe.
- If the pressure is too low, check the fuel pump, the fuel feed pipe, the fuel filter, and the fuel pressure regulator.

2. Start the engine. Hold the engine at 3,000 rpm with no load (in Park or neutral) until the radiator fan comes on.
3. Check the Primary HO2S (Sensor 1) output with the scan tool.

Does it stay at less than 0.3 V or mare than 0.6 V?

YES - Replace the Primary HO2S (Sensor 1).

NO - Go to step 4.

4. With a vacuum pump, apply vacuum to the EVAP canister purge valve from the intake manifold side.

Does it hold vacuum?

YES - Check the valve clearances and adjust if necessary. If the valve clearances are OK, replace the injectors.

NO - Replace the EVAP canister purge valve.