Oxygen Sensor Heater before Catalytic Converter, Checking
Oxygen Sensor Heater before Catalytic Converter, Checking
• The Oxygen Sensor (O2S) Heater is part of Heated Oxygen Sensor (HO2S) and cannot be replaced separately.
• When servicing electrical harness connector terminals for the Heated Oxygen Sensor (HO2S), use only gold-plated terminals.
Special tools, testers and auxiliary items required
• Multimeter.
• Wiring diagram.
Test requirements
• Fuse (in fuse panel) (SA16) OK.
• Engine Control Module (ECM) Power Supply Relay (J363) OK.
• Battery voltage at least 12.5 V.
• All electrical consumers such as, lights and rear window defroster, switched off.
• Vehicles with automatic transmission, shift selector lever into position "P" or "N".
• A/C switched off.
• Ground (GND) connections between engine/transmission/chassis OK.
• Ignition switched off.
Test procedure
- Perform a preliminary check to verify the customer's complaint. Refer to => [ Preliminary Check ] Preliminary Check.
• Voltage for Oxygen Sensor (O2S) Heater (-Z19-) (bank 1, sensor 1) and Oxygen Sensor (O2S) Heater (-Z28-) (bank 2, sensor 1) is supplied through the the Engine Control Module (ECM) Power Supply Relay (J363).
Start diagnosis
- Disconnect the 6-pin electrical harness connector - 1 - from the Heated Oxygen Sensor (HO2S) (-G39-) and Oxygen Sensor (O2S) Heater (-Z19-) (bank 1, sensor 1).
To test the Oxygen Sensor (O2S) Heater (-Z28-) (bank 2, sensor 1), perform the following steps:
- Remove the screw - arrow - retaining the coolant reservoir.
- Disconnect the electrical connector from Engine Coolant Level (ECL) Warning Switch (F66) at the bottom of the coolant reservoir and set aside the coolant reservoir with the coolant hoses - 1 - and - 2 - connected.
- Disconnect the 6-pin electrical harness connector - 1 - from the Heated Oxygen Sensor (HO2S) (-G108-) and Oxygen Sensor (O2S) Heater (-Z28-) (bank 2, sensor 1).
Checking internal resistance
- Using a multimeter, check the Heated Oxygen Sensor (HO2S) terminals 3 to 5 for an open circuit.
Specification: 2.5 to 10 ohms (at room temperature).
If the specification is not obtained:
- Replace the Heated Oxygen Sensor (HO2S) (-G39-) (bank 1, sensor 1) or Heated Oxygen Sensor (HO2S) (-G108-) (bank 2, sensor 1) before catalytic converter.
If the specified value is obtained:
Checking voltage supply
- Using a Multimeter , check the electrical harness connector terminals for voltage.
- Operate the starter briefly.
Specified value: battery voltage.
- Switch the ignition off.
If no voltage is present:
- Using a multimeter, check the Heated Oxygen Sensor (HO2S) electrical harness connector terminal 5 to ground (GND) for voltage.
- Turn key on.
- Operate the starter briefly.
Specified value: Battery voltage.
- Switch the ignition off.
If there is no voltage again:
- Using a multimeter, check the wiring connection from the Heated Oxygen Sensor (HO2S)electrical harness connector terminal to the Engine Control Module (ECM) Power Supply Relay (J363) terminal through the fuse for resistance.
Wiring resistance: 1.5 ohms max.
- If necessary, repair the wiring connection.
- If the wiring is OK:
Check Ground (GND) activation
- Using a Multimeter , check the Heated Oxygen Sensor (HO2S) electrical harness connector terminal to Ground (GND) for voltage.
- Operate the starter briefly (engine can also start)
Specified value: Battery voltage, possibly fluctuating.
- Switch the ignition off.
If the specification is not obtained:
If the manufacturers test box is being used, perform the following step.
- Install the test box (VAG1598/42).
If the manufacturers test box is not being used, perform the following step.
- Remove the Engine Control Module (ECM) (J623). Refer to=> [ Engine Control Module, Replacing ] Engine Control Module, Replacing.
- Using a multimeter, check the Heated Oxygen Sensor (HO2S) electrical harness connector to the Engine Control Module (ECM) (J623) electrical harness connector for resistance.
Oxygen Sensor (O2S) Heater (-Z19-) (bank 1, sensor 1):
Oxygen Sensor (O2S) Heater (-Z28-) (bank 2, sensor 1):
Specified value: 1.5 ohms max.
If the specification is not obtained:
- Check the wiring for a short circuit to Battery positive (+) or an open circuit.
- If necessary, repair the wiring connection.
If no malfunctions are detected:
- Replace the Engine Control Module (ECM) (J623). Refer to => [ Engine Control Module, Replacing ] Engine Control Module, Replacing
- Assembly is performed in the reverse of the removal.
After repair work, the following work steps must be performed in the following sequence:
1. Check the DTC memory. Refer to => [ Diagnostic Mode 03 - Read DTC Memory ] Diagnostic Mode 03 - Read DTC Memory.
2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Mode 04 - Erase DTC Memory.
3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.