Oxygen Sensor (O2S) and Oxygen Sensor Control Before Three Way Catalytic Converter (TWC), Checking
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
- VAG 1526 multimeter or VAG 1715 multimeter
- VAG 1594 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.
Checking primary voltage
- Disconnect 4-pin harness connector (brown) to Heated Oxygen Sensor (HO2S) -G39- (-1-).
- 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.
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).
- Generate readiness code.
Checking oxygen sensor wires
- Connect test box to control module wiring harness.
- 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 Ohms
- Also check wires for short circuit to B+ and Ground (GND).
Specified value: Infinity Ohms
If no wiring faults are found:
- Replace Motronic Engine Control Module (ECM) -J220-.