P0172

DTC P0171: Fuel System Too Lean
DTC P0172: Fuel System Too Rich

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: Manifold absolute pressure (MAP) sensor
P1162, P1166, P1167: A/F sensor (Sensor 1) heater
P0137, P0138: Secondary HO2S (Sensor 2)
P0141: Secondary HO2S (Sensor 2) heater
P1259: VTEC system

1. Check the fuel pressure.

Is fuel pressure OK?

YES - Go to step 2.

NO - Check these items:

- If the pressure is too high, replace the fuel pressure regulator.
- If the pressure is too low, check the fuel pump, the fuel feed pipe, the fuel filter, and replace 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. Turn the ignition switch OFF.




4. With a vacuum pump, apply vacuum to the evaporative emission (EVAP) canister purge valve (A) from the evaporative emission (EVAP) canister side.

Does it hold vacuum?

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

NO - Replace the EVAP canister purge valve.