Cruze

DTC P1166

The heated oxygen sensors (HO2S) are used for fuel control and catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the engine is started, the control module operates in an open loop mode, ignoring the HO2S signal voltage while calculating the air to fuel ratio. The control module supplies the HO2S with a reference, or bias voltage of about 450 mV. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0-1000 mV. This voltage will fluctuate above and below the bias voltage. Once sufficient HO2S voltage fluctuation is observed by the control module, closed loop is entered. The control module uses the HO2S voltage to determine the air to fuel ratio. An HO2S voltage that increases above bias voltage toward 1000 mV indicates a rich fuel mixture. An HO2S voltage that decreases below bias voltage toward 0 mV indicates a lean fuel mixture.

The heating elements inside each HO2S heat the sensor to bring the sensor up to operating conditions faster. This allows the system to enter closed loop earlier and the control module to calculate the air to fuel ratio sooner.

The HO2S utilizes the following circuits:

The engine control module (ECM) detects that the HO2S voltage is less than 350 mV and the air/fuel ratio is less than 13.5:1 during power enrichment mode.

DTC P1166 00 are Type B DTCs.

DTC P1166 00 are Type B DTCs.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

DTC Type Reference

Engine Controls Schematics

Scan Tool Reference

Control Module References

1. Engine running, observe the scan tool HO2S Sensor 1 voltage parameter. The reading should fluctuate above and below the range of 350-550 mV.
2. Operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that you observed from the freeze frame/failure records data.

1. Ignition OFF, disconnect the harness connector at the B52A Heated Oxygen Sensor 1.
2. Engine running, verify the scan tool HO2S Sensor 1 parameter is between 350-500 mV.

⇒	If less than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the K20 Engine Control Module.

3. Verify that none of the following conditions exist:

•	Lean fuel injectors

•	Water intrusion in the HO2S harness connector

•	Low fuel system pressure

•	Fuel that is contaminated-Refer to Alcohol/Contaminants-in-Fuel Diagnosis

•	Exhaust leaks near the HO2S

•	Contaminated HO2S--Silicon

•	Engine vacuum leaks

⇒	If you find any of the above conditions, repair as necessary.

4. If all circuits test normal, test or replace the B52A Heated Oxygen Sensor 1.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.