P0171

DTC P0171: Fuel System Too Lean

Special Tools Required
Vacuum pump/gauge, 0 - 30 in.Hg, Snap-on YA4000A or equivalent, commercially available

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

P0134, P1166, P1167: A/F sensor (Sensor 1) heater*2

P0133, P1157, P2238, P2252, P2A00: A/F sensor (Sensor 1)*3

P0134, P0135: A/F sensor (Sensor 1) heater*3

P0137, P0138: Secondary HO2S (Sensor 2)

P0141: Secondary HO2S (Sensor 2) heater

(P2646, P2647)*5: VTEC system

* 3: 2004-2005 models
* 5: 2005 model

1. Check the fuel pressure.
- 2004-2005 M/T Models.
- 2004-2005 CVT Models.

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 line.
- If the pressure is too low, check the fuel pump, the fuel feed line, the fuel filter, and the fuel pressure regulator.

2. Start the engine. Hold the engine speed at 3,000 rpm without load (in Park or neutral) until the radiator fan comes on.
3. Check the A/F sensor (Sensor 1) output with the HDS.

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. Disconnect the vacuum hose from the EVAP canister purge valve (A), and connect a vacuum pump/gauge, 0 - 30 in.Hg, to the hose.

Does it hold vacuum?

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

NO - Replace the EVAP purge valve.