Oxygen Sensor Heater After Catalytic Converter, Checking
Diagnostic Procedures
Oxygen Sensor Heater after Catalytic Converter, Checking
• When servicing terminals 3 and 4 in harness connector of oxygen sensors, use only gold-plated terminals.
Special tools, testers and auxiliary items required
• Multimeter (VAG1526) or multimeter (VAG1715)
• Connector test kit (VAG1594)
• Wiring diagram
Test requirements
• Fuses in E-box (in plenum chamber, left) must be OK:
• Motronic Engine Control Module (ECM) Power Supply Relay (J271) 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 4-pin harness connector to the respective oxygen sensor:
• Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) (G130), bank 1, 4-pin harness connector 1-,
• Oxygen Sensor (O2S) 2 Behind Three Way Catalytic Converter (TWC) (G131), bank 2, 4-pin harness connector 3-,
• 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 1 +2 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 4: Reset/erase diagnostic data.
- Generate readiness code.
If specified value is not obtained:
- Connect multimeter to terminal 1 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 4-pin connector terminal 1 to Motronic Engine Control Module (ECM) Power Supply Relay (J271) according to wiring diagram:
- Erase DTC memory of Engine Control Module (ECM) , Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code.
If specified value is obtained:
- Check Ground (GND) activation of the respective oxygen sensor heater.
Checking Ground (GND) activation
- Connect test box to control module wiring harness , connect test box for wiring test.
- 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+ or Ground (GND).
Specified value: infinite ohms
- Erase DTC memory of Engine Control Module (ECM) , Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code.
If no malfunctions are found in wires:
- Replace Motronic Engine Control Module (ECM) (J220).