GM Service Manual Online
For 1990-2009 cars only

Object Number: 896230  Size: MF

Circuit Description

The heated oxygen sensor (HO2S) bank 2 sensor 2 is threaded into the cylinder 2, 4, 6 exhaust pipe behind the pre-converter. Cylinders 2, 4, 6 are closest to the front of the vehicle. The sensor is an electrical source that responds to oxygen content out of the pre-converter. When the sensor reaches approximately 316°C (600°F), it produces a voltage based on the difference in oxygen between the atmosphere and the exhaust gas. The engine control module (ECM) sends a bias voltage, 421-479 mV on the signal line, which is pulled up through high resistance. When the HO2S bank 2 sensor 2 is cold, it produces no voltage and has extremely high internal resistance. The internal resistance of the sensor is much greater than the resistance of the bias pull-up resistor. However, when the sensor heats up, it produces voltage that overrides the bias voltage. This voltage is read by the ECM to determine the efficiency of the catalytic converter. Under normal conditions, low sensor voltage means high oxygen content/lean air-fuel mixture and vice versa. Normal sensor readings at steady cruise with a properly functioning catalytic converter will be around 500-800 mV. DTC P0160 sets when the HO2S bank 2 sensor 2 signal is inactive.

Conditions for Setting the DTC

DTC P0160 will set if HO2S bank 2 sensor 2 is inactive, the voltage is not fluctuating outside the 421-479 mV range when:

    • The condition exists for longer than 1 minute.
    • The engine has been running at least 90  seconds after the ECT has reached 4°C (40°F).
    • The calculated converter temperature is less than 940°C (1724°F).
    • The commanded air/fuel ratio is 14.7:1.
    • The battery voltage is greater than 11 volts.

DTC P0160 diagnostic runs continuously once the above conditions have been met.

DTC P0160 is a type B DTC.

Diagnostic Aids

Important: If DTC P0056, P0057, or P0058 is also set, diagnose that DTC first. A heater control circuit fault may have caused DTC P0160 to set.

To locate an intermittent problem, use the scan tool to monitor HO2S bank 2 sensor 2 voltage with the engine at normal operating temperature. Bias voltage (421-479 mV) will appear on the scan tool if there is an open anywhere in the sensor circuit.


Object Number: 898753  Size: FP