P1171

DTC P1171 Fuel System Lean During Acceleration




System Description
The PCM's internal circuitry can identify if the vehicle fuel system is capable of supplying adequate amounts of fuel during heavy acceleration (power enrichment). When a power enrichment mode of operation is requested during a closed loop operation (by heavy acceleration), the PCM provides additional fuel to the engine. Under these conditions the PCM should detect a rich condition. Whenever this rich exhaust is not detected, a DTC P1171 sets. A plugged fuel filter or restricted fuel line can prevent adequate amounts of fuel from being supplied during power enrichment mode.

Conditions for Running the DTC
- No active oxygen sensor DTCs
- The engine coolant temperature is more than 20° C (70° F).
- The engine has been running for more than 20 seconds.
- The engine is operating in a closed loop operation.

Conditions for Setting the DTC
- The O2S 1 voltage is less than 300 mV for 5 seconds
- The engine is in the power enrichment mode

Action Taken When the DTC Sets
- The PCM records the operating conditions at the time the diagnostic fails. The Failure Records buffers stores this information.
- A history DTC is stored.

Conditions for Clearing the DTC
- A history DTC clears after 40 consecutive warm up cycles without a fault.
- The scan tool can clear the DTC.

Diagnostic Aids
- A restricted fuel filter can supply adequate amounts of fuel at idle, but may not be able to supply enough fuel during heavy acceleration. Water or alcohol in the fuel may cause low O2S 1 voltage during acceleration.
- Check for faulty or plugged fuel injectors.

Steps 1 - 4:

Steps 5 - 6:

Test Description
The numbers below refers to the step numbers on the diagnostic table:
1. The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data captured when this DTC sets. The scan tool stores this data for later reference.
4. This step checks to see if the O2S 1 is operating properly
6. If no malfunctions are present at this point and no additional DTCs were set, refer to the Diagnostic Aids for additional checks and information.