Oxygen Sensor Heater before Catalytic Converter, Checking

Oxygen Sensor Heater Before Catalytic Converter, Checking

NOTE: When servicing terminals in harness connector of Heated Oxygen Sensor (H02S), use only gold-plated terminals.

Recommended Special Tools, Workshop Equipment, Testers, Measuring Instruments and Auxiliary Items
- V.A.G 1526 portable multimeter or V.A.G 1715 multimeter
- Adapter set V.A.G 1594
- Wiring diagram

Test Conditions
- Corresponding fuses of Heated Oxygen Sensor (HO2S) -G39- must be OK
- Ignition switched off.

Engine Codes AMU, ATC







- Disconnect 4-pin connector to Heated Oxygen Sensor (HO2S) -G39-.
- Set multimeter to resistance measurement and connect to terminals 1 +2 on oxygen sensor connector. Check sensor heating for continuity.







Specification: 1 to 5 Ohms ~(at room temperature)

Engine Codes AWP, BEA
- Disconnect 6-pin connector to Heated Oxygen Sensor (HO2S) -G39-.
- Set multimeter to resistance measurement and connect to terminals 3+4 on oxygen sensor connector. Check sensor heating for continuity.







Specified value: 2.5 to 10 Ohms ~(at room temperature)

Continuation for All Vehicles

If an open circuit is found in the oxygen sensor heater:
- Replace Heated Oxygen Sensor (HO2S) -G39- in front of catalytic converter.
- Erase DTC memory of ECM. Diagnostic Mode 04 - Erase DTC Memory
- Generate readiness code. Generate Readiness Code

If sensor heating has continuity:
- Check voltage supply and wiring.

Voltage Supply and Wiring, Checking

Engine Codes AMU, ATC







- Set multimeter to voltage measurement and connect to terminals 1 + 2 at connector to control module.

Engine Codes AWP, BEA







- Set multimeter to voltage measurement and connect to terminals 3 + 4 at connector to control module.

Continuation for All Vehicles
- Start engine and run at idle speed.
- Measure voltage supply

Specification: Approximate battery voltage, fluctuating if necessary

If there is no voltage:
- Connect multimeter for voltage measurement to
Terminal 1 (engine code AMU, ATC)
Terminal 3 (engine code AWP, BEA)
of connector and engine Ground.
- Briefly operate starter.

Specified value: approx. battery voltage

If there is still no voltage:
- Check wire connection from
terminal 1 (engine code AMU, ATC)
Terminal 3 (engine code AWP, BEA)
to Fuel Pump (FP) Relay J17 according to wiring diagram.

If voltage was approx. battery voltage:
- Switch off ignition.
- Connect test box to ECM wiring harness. Test Box, Connecting For Wiring Test

The Engine Control Module (ECM) remains disconnected.

Engine Codes AMU, ATC
- Check wiring between test box and 4-pin connector for open circuit according to wiring diagram.
Terminal 2 + Socket 5







Wiring resistance: max. 1.5 Ohms

Engine Codes AWP, BEA
- Check wiring between test box and 6-pin connector for open circuit according to wiring diagram.
Terminal 4 + Socket 5







Wiring resistance: max. 1.5 Ohms

Continuation for All Vehicles

If no fault is detected in the wiring:
- Replace Engine Control Module (ECM).