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.

P0106, P0107, P0108, P1128, P1129: MAP Sensor
P1162, P1163,P1164,P1165: A/F Sensor (Sensor 1) *1
P1166, P1167, P1168, P1169: A/F Sensor (Sensor 1) Heater *1
P1149, P1157, P1158, P1159, P1162, P1163, P1164: A/F Sensor (Sensor 1) *2
P1166, P1167,: A/F Sensor (Sensor 1) Heater *2
P0137, P0138: Secondary HO2S (Sensor 2)
P0141: Secondary HO2S (Sensor 2) Heater
P1259: VTEC System
* 1: '00-01 M/T models
* 2: '02-03 M/T models and CVT model

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 neutral) until the radiator fan comes on.
3. Check the A/F sensor (Sensor 1) output with the scan tool.

Does it stay at less than 0.3 V or more than 1.0 V?

YES - Replace the A/F sensor (Sensor 1).

NO - Go to step 4.

4. Turn the ignition switch OFF.
5. With a vacuum pump, apply vacuum to the EVAP purge valve from the intake manifold side.

Does it hold vacuum?

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

NO - Replace the EVAP purge valve.