Oxygen Sensor Heater Before Catalytic Converter, Checking
Diagnostic Procedures
Oxygen Sensor Heaters Before Catalytic Converter, Checking
• When servicing terminals in harness connector of oxygen sensors, use only gold-plated terminals.
Special tools, testers and auxiliary items required
• Hand multimeter (V.A.G 1526) or Multimeter (V.A.G 1715)
• Test adapter kit (V.A.G 1594)
• Wiring diagram
Test conditions
• Motronic Engine Control Module (ECM) Power Supply Relay 2 (J670) must be OK, checking:
• Battery voltage (both batteries) must be at least 11.5 Volts.
• All electrical consumers such as, lights and rear window defroster must be switched off.
• For vehicles with automatic transmission, selector lever must be in " P".
• Parking brake must be engaged.
• The Ground (GND) connections between engine and body must be OK.
• Ignition switched off.
• Fuses in right instrument panel fuse holder must be OK:
Right instrument panel fuse holder
Voltage Supply and Wiring to Control Module, Checking
Test sequence
- Disconnect corresponding 6-pin harness connector to oxygen sensor to be tested: Component location
- Connect multimeter to terminals 3 +4 of connector to Engine Control Module for voltage measurement.
- Start engine and run at idle speed. Specification: at least 7.0 V
If specification is obtained:
- Switch ignition off.
- Erase DTC memory of Engine Control Module => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09, Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code => [ Readiness Code, Generating ] Monitors, Trips, Drive Cycles and Readiness Codes.
If specification is not obtained:
- Connect multimeter to terminal 3 of connector to Engine Control Module + Ground (GND) for voltage measurement. Specification: at least 11.0 V
- Switch ignition off.
If specification is not obtained:
- Check voltage supply at 6-pin connector terminal 3 to Motronic Engine Control Module (ECM) Power Supply Relay 2 (J670) according to wiring diagram:
- Erase DTC memory of Engine Control Module => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09, Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code => [ Readiness Code, Generating ] Monitors, Trips, Drive Cycles and Readiness Codes.
If specification is obtained:
- Check Ground (GND) activation of respective oxygen sensor heater.
Oxygen Sensor Heating Ground Activation, Checking
Test sequence
- Disconnect corresponding 6-pin harness connector to oxygen sensor to be tested: Component location
Cylinder bank 1
- Connect test box to Engine Control Module (ECM) (J623) wiring harness on connecting test box for wiring test, refer to Repair Manual,
Cylinder bank 2
- Connect test box to Engine Control Module (ECM) 2 (J624) wiring harness on connecting test box for wiring test, refer to Repair Manual,
Cylinder bank 1 and 2
- Check wires between test box and 6-pin connector to Engine Control Module (ECM) for open circuit according to wiring diagram. Wiring resistance: max. 1.5 ohms
- Check wires for short circuit to B+ and Ground (GND). Specification: infinite ohms
- Erase DTC memory of Engine Control Module => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09, Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code => [ Readiness Code, Generating ] Monitors, Trips, Drive Cycles and Readiness Codes.
If no malfunction is detected in the wiring replace the engine control module.