Without VAG

HEATED OXYGEN SENSOR CHECKING

NOTE: Oxygen Sensor heating is controlled by the Heated Oxygen Sensor (HO2S) Control Module, located in position # 13 of the fuse/relay panel.

PRE-TEST REQUIREMENTS
- Fuse 18 OK
- Exhaust system not leaking
- Voltage supply to Motronic Engine Control Module (ECM) OK
- Engine at normal operating temperature

ELECTRICAL TESTING
- Disconnect harness connector to oxygen sensor heater.
- START engine and let idle.
- Connect LED test light between terminals of oxygen sensor heater harness connector.

^ LED should light

^ IF NOT check fuse and wiring to Heated Oxygen Sensor Control Module.

- Fold back rubber boot at oxygen sensor signal lead, do not separate connectors.
- Connect voltmeter between exposed sensor lead and ground.

^ Voltmeter should oscillate between 0.1 and 0.9 VDC

- If reading is fixed at 0.4 - 0.6 VDC, check for open circuit between sensor and ECM.
- If reading is too low, check for grounded signal wire, intake leak, or heater element operation.
- If reading is too high, check for signal lead short to other wiring.
- If wiring is OK, replace sensor and recheck.