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
- VAG1526 multimeter or VAG1715 multimeter
- VAG1594 connector test kit
- Wiring diagram

Test requirements







- Fuses in E-box (in plenum chamber, left) must be OK:
- Motronic Engine Control Module (ECM) Power Supply Relay -J271- -position A3- must be OK, check:
- Battery voltage must be at least 11.5 volts.
- All electrical consumers such as, for example, 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- position.
- 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 -2-,
- Heated Oxygen Sensor (HO2S) 2 -G108-, bank 2, 6-pin harness connector -4-.

NOTE:
- Bank 1 = Cylinder bank 1, in direction of travel, right.
- Bank 2 = Cylinder bank 2, in direction of travel, left.

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 7.0 V

If specified value is obtained:
- Switch ignition off.
- Erase DTC memory of Engine Control Module (ECM). Diagnostic Mode 04 - Erase DTC Memory
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

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 voltage supply at 6-pin connector terminal 3 to Motronic Engine Control Module (ECM) Power Supply Relay -J271- according to wiring diagram:
- Erase DTC memory of Engine Control Module (ECM). Diagnostic Mode 04 - Erase DTC Memory
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

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. Connecting Test Box 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 ohms.

- Erase DTC memory of Engine Control Module (ECM). Diagnostic Mode 04 - Erase DTC Memory
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

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