With Generic Scan Tool

Oxygen Sensor Heater For Oxygen Sensor Before Three Way Catalytic Converter (TWC), Checking

NOTE: When servicing terminals in harness connector of Heated Oxygen Sensor (HO2S), use only gold-plated terminals.

Recommended special tools and equipment
- VAG1526 multimeter or VAG1715 multimeter
- VAG1594 connector test kit
- Wiring diagram

Test requirements
- The respective fuses of Heated Oxygen Sensor (HO2S) -G39- must be OK.
- Ignition switched off.

Engine codes AMU, ATC







- Disconnect 4-pin harness connector to Heated Oxygen Sensor (HO2S) -G39-.







- Set multimeter for resistance measurement and connect it to terminals 1 + 2 at connector for oxygen sensor. Check oxygen sensor heater for continuity.
Specified value: 1...5 Ohm (at room temperature)

Engine codes AWP, BEA
- Disconnect 6-pin harness connector to Heated Oxygen Sensor (HO2S) -G39-.







- Set multimeter for resistance measurement and connect it to terminals 3 + 4 at connector for oxygen sensor. Check oxygen sensor heater for continuity.
Specified value: 2.5...10 Ohm (at room temperature)

Continuation for all vehicles
If an open circuit is found in the oxygen sensor heater:
- Replace Heated Oxygen Sensor (HO2S) -G39-.
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data. Diagnostic Mode 4: Reset/Erase Diagnostic Data
- Generate readiness code. Readiness Code, Generating

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

Checking voltage supply and wiring

Engine codes AMU, ATC







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

Engine codes AWP, BEA







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

Continuation for all vehicles
- Start engine, and let run at idle.
- Measure voltage supply
Specified value: approx. battery voltage, possibly fluctuating

If there is no voltage:
- Connect multimeter for voltage measurement to
Terminal 1 (Engine codes AMU, ATC)
Terminal 3 (engine codes AWP, BEA) of connector and engine Ground (GND).
- Operate starter briefly.
Specified value: approx. battery voltage

If there is no voltage again:
- Check wire connections from
Terminal 1 (Engine codes AMU, ATC)
Terminal 3 (engine codes AWP, BEA) to Fuel Pump (FP) Relay -J17-according to wiring diagram.

If voltage was approximately same as battery voltage:
- Switch ignition off.
- Connect test box to control module wiring harness, connect test box for wiring test. Test Box, Connecting For Wiring Test

Engine Control Module (ECM) is not connected.

Engine codes AMU, ATC







- Check wire between test box and 4-pin connector for open circuit according to wiring diagram.
Terminal 2 + socket 5
Wire resistance: max: 1.5 Ohm

Engine codes AWP, BEA







- Check wire between test box and 6-pin connector for open circuit according to wiring diagram.
Terminal 4 + socket 5
Wire resistance: max: 1.5 Ohm

Continuation for all vehicles
If no malfunctions are found in wires:
- Replace Engine Control Module (ECM).