Checking HO2S Control Signal

Heated Oxygen Sensor Connector:

- Disconnect harness connector -1- for HO2S signal wire.
- Switch DVOM to 2 Volt (DC) measuring range.
- Connect DVOM (using adapter cables from connector test kit VW 1594) between: ECM harness connector and engine GND.
- Switch ignition ON.
^ Must be 450 (+/-) 50mV.

If NOT:
- Connect VAG 1598 Test Box (using VAG 1598/5 adapter cable) to ECM harness connector. Refer to VAG 1598 Pin Out Box Connecting. Connecting and Testing VAG 1598 Pin Out Box
^ ECM harness connector at component is not connected.
- Switch DVOM to resistance range.

Engine Control Module Harness Connector:

- Check continuity between harness connector in engine compartment and Test Box terminal 28 using wiring diagram.
^ Must be 1.0 ohm maximum.

If circuit is open:
- Repair as necessary.

If circuit is NOT open:
- Check continuity of GND connection between engine cylinder block and Test Box terminal 10 using wiring diagram.
^ Must be 1.0 ohm maximum.

If circuit is open:
- Repair as necessary.

If there is no malfunction in wiring:
- Replace ECM.