Oxygen Sensor Heater, Checking
Diagnostic Procedures
Oxygen Sensor Heater, Checking
• Cylinder bank 1 is located in direction of travel, right.
• Cylinder bank 2 is located in direction of travel, left.
• Use only gold-plated terminals when servicing terminals in harness connector.
Special tools, testers and auxiliary items required
• Multimeter (VAG1526) or Multimeter (VAG1715)
• Connector test kit (VAG1594)
• Wiring diagram
Test Prerequisites
• Fuses in E-box (plenum chamber, left) must be OK:
• Power Supply Relay (Terminal 30, B+) Relay 2 (J689), 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.
• 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.
• Coolant temperature must be at least 80 °C --> [ Diagnostic Mode 01 - Read Current System Data ] Diagnostic Modes 01 - 09.
• Ignition is switched off.
- Disconnect 6-pin harness connector - B - to Heated Oxygen Sensor (HO2S) (G39).
Sensor Heater, Checking Resistance
- Check resistance for sensor heater at connector to oxygen sensor terminal 3 +4.
Specified value: Max. 10 ohms (at room temperature)
If specified value is not obtained:
- Replace Heated Oxygen Sensor (HO2S) (G39).
- Erase DTC memory of Engine Control Module (ECM) --> [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09
- Generate readiness code --> [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.
If specified value is obtained:
- Check voltage supply and wiring to control module.
Checking Voltage Supply and Wiring
- Connect multimeter to terminal 3 (of connector to Engine Control Module -ECM-) + Ground (GND) for voltage measurement.
- Start engine, and let run at idle.
Specified value: at least 9.0 V
- Switch ignition off.
If specified value is not obtained:
- Check wire from 6-pin connector terminal 3 to Power Supply Relay (Terminal 30, B+) Relay 2 (J689) according to wiring diagram:
- Erase DTC memory of Engine Control Module (ECM) --> [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09
- Generate readiness code --> [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.
If specified value is obtained:
- Check Ground (GND) activation of oxygen sensor heater.
Checking Ground Activation
- Connect test box ((VAG1598/42)) to Engine Control Module (ECM) (J623) wiring harness using adapter cable ((VAG1598/39-2)) , 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.
Terminal 4 + socket 51
Wire resistance: max. 1.5ohms
- Also check the wire for short circuit to B+ and Ground (GND).
Specified value: infinite ohms
If no malfunctions are found in wires:
- Replace Engine Control Module (ECM) (J623) --> [ Engine Control Modules, Replacing ] Engine Control Modules, Replacing.
Oxygen Sensor Heater 2 (Z28) Test Sequence
- Disconnect 6-pin harness connector - A - to Heated Oxygen Sensor (HO2S) 2 (G108).
Checking Resistance
- Check resistance for sensor heater at connector to oxygen sensor terminal 3 +4.
Specified value: Max. 10 ohms (at room temperature)
If specified value is not obtained:
- Replace Heated Oxygen Sensor (HO2S) 2 (G108).
- Erase DTC memory of Engine Control Module (ECM) --> [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09.
- Generate readiness code --> [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.
If specified value is obtained:
- Check voltage supply and wiring to control module.
Checking Voltage Supply and Wiring
- Connect multimeter to terminal 3 (of connector to Engine Control Module -ECM-) + Ground (GND) for voltage measurement.
- Start engine, and let run at idle.
Specified value: at least 9.0 V
- Switch ignition off.
If specified value is not obtained:
- Check wire from 6-pin connector terminal 3 to Power Supply Relay (Terminal 30, B+) Relay 2 (J689) according to wiring diagram:
- Erase DTC memory of Engine Control Module (ECM) --> [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09.
- Generate readiness code --> [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.
If specified value is obtained:
- Check Ground (GND) activation of oxygen sensor heater.
Checking Ground Activation
- Connect test box ((VAG1598/42)) to Engine Control Module 2 (J624) wiring harness using adapter cable ((VAG1598/39-2)) , 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.
Terminal 4 + socket 51
Wire resistance: max. 1.5ohms
- Also check the wire for short circuit to B+ and Ground (GND).
Specified value: infinite ohms
If no malfunctions are found in wires:
- Replace Engine Control Module 2 (J624).