P1171
SYSTEM DESCRIPTIONOxygen sensors (O2S) are used for fuel control and post catalyst monitoring. Each O2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The O2S must reach operating temperature to provide an accurate voltage signal. A heating element in O2S 2 minimizes the time required for the sensor to reach operating temperature. The powertrain control module (PCM) supplies the O2S with a reference, or bias, voltage of about 450 mV. When the engine is first started the PCM operates in open loop, ignoring the O2S voltage signal. Once the O2S reaches operating temperature and Closed Loop is achieved, the O2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage. High O2S voltage indicates a rich exhaust stream. Low O2S voltage indicates a lean exhaust stream. If the PCM detects that O2S 1 voltage stays below a specified value, DTC P1171 will set.
CONDITIONS FOR RUNNING THE DTC
- DTCs P0122, P0123, P0131, P0132, P0133, P0134 are not set.
- The ECT Sensor parameter is more than 20°C (68°F).
- The Engine Run Time parameter is more than 20 seconds.
- The Loop Status parameter is closed.
- The Power Enrichment parameter is Active.
CONDITIONS FOR SETTING THE DTC
The PCM detects that the O2S 1 parameter is less than 300 mV for 5 seconds.
ACTION TAKEN WHEN THE DTC SETS
- The control module stores the DTC information into memory when the diagnostic runs and fails.
- The malfunction indicator lamp (MIL) will not illuminate.
- The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
- The driver information center, if equipped, may display a message.
CONDITIONS FOR CLEARING THE DTC
- A current DTC Last Test Failed clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
- Clear the DTC with a scan tool.
DIAGNOSTIC AIDS
- The fuel pressure-System will run lean if the fuel pressure is too low. Monitor the fuel pressure while driving the vehicle at various road speeds and loads in order to confirm. Refer to Fuel System Diagnosis. Component Tests and General Diagnostics
- The MAP sensor-An output that causes the PCM to sense a lower than normal manifold pressure, or high vacuum, can cause the system to go lean. Disconnecting the MAP sensor will allow the PCM to substitute a fixed or defaulted value for the MAP sensor. When the lean condition is gone when the sensor is disconnected, substitute a known good sensor and recheck.
- A fuel contamination-Water, in even small amounts near the fuel pump inlet, can be delivered to the fuel injector. The water causes a lean exhaust condition.
- The O2S harness-The O2S 1 pigtail may be mis-positioned and contacting the exhaust manifold.
- An engine misfire-A misfire will result in unburned oxygen in the exhaust, which can cause a lean condition. Refer to Symptoms - Computers and Control Systems. Symptom Related Diagnostic Procedures
- A plugged fuel filter- A plugged fuel filter can cause a lean condition.
TEST
