P1171

DTC P1171 Fuel System Lean During Acceleration




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

Conditions for Setting the DTC
- No related Diagnostic Trouble Codes.
- Engine is operating in "Closed Loop".
- Engine coolant temperature is above 60 °C (140 °F).
- While in "power enrichment" mode the oxygen sensor voltage remains below 400 mV for 3 seconds.

Action Taken When the DTC Sets
- The PCM will illuminate the malfunction indicator lamp (MIL) the first time the fault is detected.
- The PCM will store conditions which were present when the Diagnostic Trouble Code was set as Freeze Frame and in the Failure Records data.

Conditions for Clearing the MIL/DTC
- The PCM will turn the MIL OFF on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present.
- A history Diagnostic Trouble Code P1171 will clear after 40 consecutive warm-up cycles have occurred without a fault.

Diagnostic Aids
A malfunction in the HO2S heater ignition feed or ground circuit may cause a Diagnostic Trouble Code P1133 to set. Check HO2S heater circuitry for intermittent faults or poor connections. If connections and wiring are OK and Diagnostic Trouble Code P1134 continues to set, replace the Bank 1 HO2S 1.
Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the Diagnostic Trouble Code to be set occurs. This may assist in diagnosing the condition.

Steps 1 - 5:

Steps 6 - 8:

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Chart:
3. A condition that affects other heated oxygen sensors indicates probable contamination. To avoid damaging the replacement sensors, correct the condition which caused the contamination before replacing the affected sensors.
5. This step checks for conditions which may cause the heated oxygen sensor to appear faulty. Correct any of the described conditions if present.
11. To avoid damaging replacement sensors, correct the condition which caused the contamination before replacing the affected sensors.