Heater For Oxygen Sensor Before Catalytic Converter, Checking
Heater for Oxygen Sensor before Catalytic Converter, Checking
• Oxygen sensor signals are monitored via On Board Diagnostic (OBD).
- Check DTC memory. If an oxygen sensor malfunction relating to heating circuit is displayed.
- Disconnect respective harness connector for oxygen sensor.
2 4-pin harness connector for Heated Oxygen Sensor (HO2S) 2 (G108) and Oxygen Sensor (O2S) 2 Heater (Z28) before catalytic converter, bank 2
3 4-pin harness connector for Heated Oxygen Sensor (HO2S) (G39) and Oxygen Sensor (O2S) Heater (Z19) before catalytic converter, bank 1
Test Prerequisites
• The respective fuses of Heated Oxygen Sensor (HO2S) (G39) and Heated Oxygen Sensor (HO2S) 2 (G108) must be OK:
- Coolant temperature must be at least 80 °C => [ Diagnostic Mode 01 - Read Current System Data ] Diagnostic Modes 01 - 09, Diagnostic mode 1: Check measured values; PID 5, Coolant temperature.
- Perform continuity test (resistance measurement) between terminals 3 and 4 of respective sensor connector using portable multimeter (VAG1526).
Specified value at room temperature: 2.5 to 4 ohms
• At higher temperatures, resistance climbs sharply.
If specified value is not reached, replace respective Heated Oxygen Sensor (HO2S) (G39)/Heated Oxygen Sensor (HO2S) 2 (G108).
If specified value is obtained, check voltage supply.
Voltage Supply, Checking
• The respective fuses of Heated Oxygen Sensor (HO2S) (G39) and Heated Oxygen Sensor (HO2S) 2 (G108) must be OK:
- Connect voltage test lamp (VAG1527) between terminal 3 of respective oxygen sensor connector and engine Ground (GND).
- Operate starter briefly.(Do not let engine run longer than 2 minutes, because of malfunction entry)
Voltage test lamp must light up.
- If voltage test lamp does not light up, check wire connection from terminal 3 of the respective oxygen sensor connector via fuse to Fuel Pump (FP) Relay (J17) for open circuit or short circuit.
- If fuses and wire connection are OK, but voltage test lamp does not light up anyway, check Fuel Pump (FP) relay => [ Fuel Pump Relay, Checking ].
- If voltage supply is OK, check wire connections.
Wire Connections, Checking
- Check the following wire connections using portable multimeter (VAG1526).
Heated Oxygen Sensor (HO2S) (G39) before catalytic converter bank 1, with Oxygen Sensor (O2S) Heater (Z19)
Heated Oxygen Sensor (HO2S) 2 (G108) before catalytic converter bank 2, with Oxygen Sensor (O2S) 2 Heater (Z28)
- Operate starter briefly. (Do not let engine run longer than 2 minutes, because of malfunction entry)
Specified value: approx. battery voltage
- Switch ignition off.
If specified value is not obtained, check wire connection.
- Connect test box (VAG1598/31) to wiring harness of Engine Control Module (ECM),
- Check the following wire connections for open circuit.
Heated Oxygen Sensor (HO2S) (G39) before catalytic converter bank 1, with Oxygen Sensor (O2S) Heater (Z19)
Heated Oxygen Sensor (HO2S) 2 (G108) before catalytic converter bank 2, with Oxygen Sensor (O2S) 2 Heater (Z28)
- Repair open circuit in wiring or short circuit if necessary.
- If wire connection is OK but there is no Ground (GND) activation present for oxygen sensor heater, replace Engine Control Module (ECM), refer to Repair Manual and generate readiness code again => [ Readiness Code, Generating ] Monitors, Trips, Drive Cycles and Readiness Codes.