Scan Tester Procedure (California)

Access scan tester service data item No. 11. Tester should display sensor voltage. Ensure engine is at normal operating temperature. See HO2S OPERATING VOLTAGE SPECIFICATIONS  table.

1. Measure power supply voltage. Disconnect both HO2S harness connectors. Turn ignition on. Using DVOM, measure voltage between harness connector terminal No. 3 (Red wire) of front sensor, terminal No. 1 (Red wire) of rear sensor and vehicle ground. If voltage measured is less than battery voltage, inspect and repair circuit as needed.
2. Check continuity of ground circuit to ECM. Turn ignition off. Disconnect ECM harness connector. For front sensor, connect jumper wire between ECM harness connector terminal No. 6 (White wire) connector No. C50-5) and vehicle ground. See Figure and Figure . Check resistance between front sensor harness connector terminal No. 1 (White wire) and vehicle ground. If continuity does not exist, inspect and repair circuit as needed.
3. Move jumper wire to ECM harness connector terminal No. 7 (White wire, connector No. C50-5). See Figure and Figure . Check resistance between rear sensor harness connector terminal No. 3 (White wire) and vehicle ground. If continuity does not exist, inspect and repair circuit as needed.
4. Check continuity of sensor ground circuits. Using ohmmeter, check resistance between harness connector terminals No. 2 and 4 (Black and Orange wires) of both sensors and vehicle ground. If continuity does not exist, inspect and repair circuits as needed.