With Generic Scan Tool

Oxygen Sensor (O2S) And Oxygen Sensor Control 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:
- Battery voltage must be at least 11.5 volts.
- All electrical consumers like, for example, lights and rear window heating must be switched off.
- Parking brake must be engaged or else daylight driving lights will be switched on.
- If vehicle is equipped with an A/C system, it must be switched off.
- Ground (GND) connections between engine and chassis must be OK.
- Exhaust system must be properly sealed between catalytic converter and cylinder head.
- Oxygen sensor heaters for oxygen sensors before catalytic converter must be OK. Oxygen Sensor (O2S) Heating -Z19- Before TWC, Checking

Checking primary voltage
Engine codes AMU, ATC







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







- Use adapter cables from V.A.G 1594 to connect multimeter to terminals 3 + 4 (ECM connector) for voltage measurement.
- Start engine and measure primary voltage.
Specified value: 0.40 to 0.50 Volts
- Switch ignition off.

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







- Connect multimeter between terminal 1 and 5 for voltage measurement.
- Switch on ignition and measure primary voltage.
Specified value: 0.40 to 0.50 Volts.
- Switch ignition off.

Continuation for all vehicles
If specified value is not obtained:
- Test oxygen sensor wires

If specified value is obtained:
- 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

Checking oxygen sensor wires
- Connect test box to control module wiring harness, connect test box for wiring test. Test Box, Connecting For Wiring Test

Engine codes AMU, ATC







- Check wires between test box and 4-pin connector to Engine Control Module (ECM) for open circuit according to wiring diagram.
Wire resistance: max: 1.5 Ohm







Engine codes AWP, BEA







- Check wires between test box and 6-pin connector to Engine Control Module (ECM) for open circuit according to wiring diagram.
Wire resistance: max: 1.5 Ohm







Continuation for all vehicles
- Also check wires for short circuit to B+ and Ground (GND).
Specified value: Infinite Ohm

If no malfunctions are found in wires:
- Replace Motronic Engine Control Module (ECM) -J220-.