Oxygen Sensor Heater For Oxygen Sensors Before Catalytic Converter, Checking

Oxygen Sensor Heater For Oxygen Sensors Before Catalytic Converter, Checking

NOTE: When servicing terminals in harness connector of oxygen sensors, use only gold-plated terminals.

Recommended special tools and equipment
- V.A.G 1526 multimeter or V.A.G 1715 multimeter
- V.A.G 1594 connector test kit
- Wiring diagram

Test requirements







- Fuses in E-box (plenum chamber, left) must be OK
- Motronic Engine Control Module (ECM) Power Supply Relay 2 -J670- -position A1- must be OK, check
- Battery voltage must be at least 11.5 volts.
- All electrical consumers such as, lights and rear window defroster must be switched off.
- Parking brake must be engaged or else daylight driving lights will be switched on.
- For vehicles with automatic transmission, selector lever must be in -P-.
- If vehicle is equipped with an A/C system, it must be switched off.
- Ground (GND) connections between engine and chassis must be OK.

Test sequence







- Disconnect 6-pin harness connector to the respective oxygen sensor:
- Heated Oxygen Sensor (HO2S) -G39-, bank 1, 6-pin harness connector -1-,
- Heated Oxygen Sensor (HO2S) 2 -G108-, bank 2, 6-pin harness connector -4-.

Checking voltage supply and wiring to control module







- Connect multimeter to terminals 3 + 4 of connector to Engine Control Module (ECM) for voltage measurement.
- Start engine, and let run at idle.
Specified value: at least 8.0 V

If specified value is obtained:
- Switch ignition off.
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data. Diagnostic Mode 04 - Erase DTC Memory
- Generate readiness code. Readiness Code

If specified value is not obtained:







- Connect multimeter to terminal 3 of connector to Engine Control Module (ECM) + Ground (GND) for voltage measurement.

Specified value: at least 11.0 V

- Switch ignition off.

If specified value is not obtained:
- Check wire between 6-pin connector terminal 3 and Motronic Engine Control Module ECM) Power Supply Relay 2 -J670- for open circuit according to wiring diagram.

Wire resistance: max. 1.5 ohms

- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data. Diagnostic Mode 04 - Erase DTC Memory
- Generate readiness code. Readiness Code

If specified value is obtained:
- Check Ground (GND) activation of the respective oxygen sensor heater.

Checking Ground (GND) activation of oxygen sensor heating
- 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.
Wire resistance: max. 1.5 ohms







- Also check wires for short circuit to B+ or Ground (GND).
Specified value: infinity ohm
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data. Diagnostic Mode 04 - Erase DTC Memory
- Generate readiness code. Readiness Code

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