For 1990-2009 cars

The heated oxygen sensor (HO2S) bank 2 sensor 1 is threaded into the cylinder 2, 4, 6 exhaust manifold (cylinders 2, 4 and 6 are closest to the radiator). The sensor is equipped with a heater element to decrease the amount of time required to enter closed loop fuel control. The ECM controls the heater by pulsing circuit 551 to ground. When the heater is commanded Off (circuit not grounded), the voltage level at the ECM should be high (ignition voltage). When the heater is commanded On (circuit grounded), the voltage level at the ECM should be low. The ECM heater feedback circuit uses a pull-up voltage (1.6-3.6 volts), which allows the ECM to individually differentiate between an open, short to ground or short to voltage. DTC P0050 will set if the ECM detects an open heater control circuit when the HO2S bank 2 sensor 1 heater is commanded Off with the engine running.

### DTC PARAMETERS

DTC P0050 will set if the HO2S bank 2 sensor 1 heater feedback voltage is between 1.6-3.6 volts (ECM pull-up voltage), indicating an open circuit. The heater is commanded Off when:

• | The condition exists for longer than 0.4 seconds.

• | The engine is running.

• | The battery voltage is between 11.0-15.0 volts.

DTC P0050 diagnostic runs continuously once the above conditions have been met.

P0050 is a type B DTC.

### Diagnostic Aids

To locate an intermittent problem, use the Scan tool to monitor the HO2S HEATER BN. 2 SEN. 1 with the engine running. The voltage should fluctuate greater than 1 volt, indicating the circuit is functioning correctly. Compare this parameter to the HO2S HEATER BN. 1 SEN. 1 parameter. Both parameters should closely match. The voltage will not change greater than 1 volt when an open circuit occurs.

Heater element resistance: 2.4-9.2 ohms