Oxygen Sensor Heater For O2 Sensor Before TWC, Checking

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


NOTE:
- Vehicle must be raised before connector for oxygen sensor is accessible.
- 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.
- Ignition switched off.

Test sequence (Vehicles with engine code AEG)







- Unscrew protective cover (arrows) and disconnect 4-pin harness connector (black) -1- to Heated Oxygen Sensor (HO2S) -G39- before catalytic converter.







- Check resistance for sensor heater at connector to oxygen sensor terminal 1 + 2: Specified value: 1,0...5,0 Ohms(at room temperature)

If specified value is not obtained:
- Replace Heated Oxygen Sensor (HO2S) 1 Bank 1 -G39- before catalytic converter.
- 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. Monitors, Trips, Drive Cycles and Readiness Codes

If specified value is obtained:
- Check Ground (GND) activation of oxygen sensor heater.
- Connect test box to control module wiring harness, connect test box for wiring test. Test Box, Connecting For Wiring Test







- Check wires between test box and 4-pin connector to Engine Control Module (ECM) for open circuit according to wiring diagram. Terminal 2 + socket 27: Wire resistance: max. 1.5 Ohms
- Also check wires for short circuit to B+ and Ground (GND). Specified value: Infinite Ohms
- Check wire between 4-pin connector terminal 1 and Fuel Pump (FP) Relay -J17- for open circuit according to wiring diagram. Wire resistance: max. 1.5 Ohms

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

Test sequence (Vehicles with engine code AVH, AZG, BDC)







- Unscrew protective cover (arrows) and disconnect 6-pin harness connector (black) -1- to Heated Oxygen Sensor (HO2S) -G39- before catalytic converter.







- Check resistance for sensor heater at connector to oxygen sensor terminal 3 + 4. Specified value: 2.5...10.0 Ohms (at room temperature)

If specified value is not obtained:
- Replace Heated Oxygen Sensor (HO2S) 1 Bank 1 -G39- before catalytic converter.
- 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. Monitors, Trips, Drive Cycles and Readiness Codes

If specified value is obtained:
- Check Ground (GND) activation of oxygen sensor heater.
- Connect test box to control module wiring harness, connect test box for wiring test. Test Box, Connecting For Wiring Test







- Check wires between test box and 6-pin connector to Engine Control Module (ECM) for open circuit according to wiring diagram. Terminal 4 + socket 5: Wire resistance: max. 1.5 Ohms
- Also check wires for short circuit to B+ and Ground (GND). Specified value: Infinite Ohms
- Check wire between 6-pin connector terminal 3 and the Fuel Pump (FP) Relay -J17- for open circuit according to wiring diagram. Wire resistance: max. 1.5 Ohms

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