P1171

DTC P1171 Fuel Supply System Lean During Power Enrich

System Description
The internal circuitry of the engine control module (ECM) can identify if the vehicle fuel system is capable of supplying adequate amounts of fuel during heavy acceleration (power enrichment). When a power enrichment (PE) mode of operation is requested during Closed Loop operation (by heavy acceleration), the ECM will provide more fuel to the engine. Under these conditions the ECM should detect a rich condition. If this rich exhaust is not detected at this time, Diagnostic Trouble Code (DTC) P1171 will set. A plugged fuel filter or restricted fuel line can prevent adequate amounts of fuel from being supplied during power enrichment mode.

Conditions for Setting the DTC
- Engine is operating in Closed Loop and in RE mode.
- Engine Coolant Temperature (ECT) is above than 60 °C (140 °F).
- Oxygen sensor (O2S 1) voltage is less than 400 mv in PE mode.
- No related malfunctions.
- Air-to-fuel ratio is less or equal to 13.5:1.

Action Taken When the DTC Sets
- The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.
- A history DTC is stored.
- Coolant fan turns on.

Conditions for Clearing the MIL/DTC
- A history DTC will clear after 40 consecutive warm-up cycles without a fault.
- DTC(s) can be cleared by using the scan tool.

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 fuel may cause low O2S 1 voltage during acceleration.

Check for adequate amount of fuel in the Tank.

When the engine is idling or at steady cruise, the O2S 1 voltage should vary from between approximately 100 mv to 900 mv. During power enrichment mode, more fuel is needed, and the O2S 1 should rise above 447 mv. Check for faulty or plugged injector(s).

Steps 1 - 6:

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
1. The On-Board Diagnostic (OBD II) System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.
4. This step checks to see if the O2S 1 is operating properly.
6. If no faults have been found at this point and no additional DTCs were set, refer to "Diagnostic Aids" for additional checks and information.