Electronic Control System Gas Plus Engines – 019-349   Heated Oxygen Sensor Circuit

Disconnect engine harness ECM connectors 1 and 2 from the ECM. Disconnect the 31-pin engine harness connector from the 31-pin OEM harness connector. Disconnect the heated oxygen sensor from the engine harness. Set the multimeter to measure resistance.

Measure the resistance from the heated oxygen heater (+) pin in the engine harness 31-pin connector to the corresponding pin in the engine harness sensor connector.

The multimeter must show a closed circuit (10 ohms or less).

If the circuit is not closed, there is an open circuit in the heated oxygen heater (+) wire.

Repair or replace the engine harness. Refer to Procedure 019-203, 019-208, or 019-043.

Measure the resistance from the heated oxygen heater (-) pin in the engine harness ECM connector 1 to the corresponding pin in the engine harness sensor connector.

The multimeter must show a closed circuit (10 ohms or less).

If the circuit is not closed, there is an open circuit in the heated oxygen heater (-) wire.

Repair or replace the engine harness. Refer to Procedure 019-203, 019-204, or 019-043.

Disconnect engine harness ECM connectors 1 and 2 from the ECM. Disconnect the 31-pin engine harness connector from the 31-pin OEM harness connector. Disconnect the heated oxygen sensor from the engine harness. Set the multimeter to measure resistance.

Measure the resistance from the heated oxygen heater (+) pin in the engine harness 31-pin connector to engine block ground.

The multimeter must show an open circuit (100k ohms or more).

If the circuit is not open, there is a short circuit to ground in the heated oxygen heater (+) wire.

Repair or replace the engine harness. Refer to Procedure 019-208 or 019-043.

Measure the resistance from the heated oxygen heater (-) pin in the engine harness ECM connector 1 to engine block ground.

The multimeter must show an open circuit (100k ohms or more) for both signal wire checks.

If the circuit is not open, there is a short circuit to ground in the heated oxygen heater (-) wire. Repair or replace the engine harness. Refer to Procedure 019-204, or 019-043.

Disconnect engine harness ECM connectors 1 and 2 from the ECM. Disconnect the 31-pin engine harness connector from the 31-pin OEM harness connector. Disconnect the heated oxygen sensor from the engine harness.

Set the multimeter to measure resistance.

Measure the resistance from the heated oxygen heater (+) pin in the engine harness 31-pin connector to all other pins in engine harness ECM connectors 1 and 2.

The multimeter must show an open circuit at all pins.

If any pin-to-pin check does not show an open circuit, there is a short circuit between the applicable pins.

Repair or replace the engine harness. Refer to Procedure 019-208, 019-204, or 019-043.

Measure the resistance from the heated oxygen heater (-) pin in engine harness ECM connector 1 to all other pins in the connector and to all pins in engine harness ECM connector 2.

Repair or replace the engine harness. Refer to Procedure 019-204, or 019-043.