Heater Check

Oxygen Sensor Heater For Heated Oxygen Sensor (HO2S) -G39-, Checking

Special tools and equipment

- V.A.G 1551 scan tool (or VAG 1552 mobile scan tool) with VAG 1551/3B cable
- VAG 1598/31 adapter cable
- VAG 1526 multimeter or VAG 1715 multimeter
- VAG 1594 connector test kit
- Wiring diagram

Test requirements







- Fuse no. 34 must be OK.
- Battery voltage must be at least 11.5 volts.
- Fuel Pump (FP) relay must be OK.

Test sequence
- Connect V.A.G 1551 scan tool (VAG 1552). Start engine and select the Engine Control Module (ECM) using address word 01 (connecting scan tool and selecting ECM). Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks/Connecting VAG 1551 Scan Tool", Connecting VAG 1551 Scan Tool

Indicated on display:


Rapid data transfer HELP
Select function XX


- Press buttons -0- and -8- to select "Read measuring value block" function 08. Press - Q- button to confirm input.

Indicated on display:


Read measuring value block HELP
Enter display group number XXX


- Press buttons -0-, -4- and -1- to select "Display group number 41". Press -Q- button to confirm input.

Indicated on display: (1 to 4 - display fields)


Read measuring value block 41 ->
1 2 3 4


- Check the status of the oxygen sensor heater in display field 2: Display: Htng.bef.Cat.ON/OFF

If the indication remains constant at OFF:







- Disconnect 6-pin harness connector (black) to Heated Oxygen Sensor (HO2S) - G39- (item no. 2).







- Set multimeter for resistance measurement and connect it to terminals 3 + 4 at connector for oxygen sensor. Check oxygen sensor heater for continuity.
Specification: 2.5 to 10 Ohms (at room temperature)

If a short circuit is found in the oxygen sensor heater:
- Replace Heated Oxygen Sensor (HO2S) - G39-.

If oxygen sensor heater has continuity:
- heck voltage supply and wiring.

Checking voltage supply and wiring







- Set multimeter for voltage measurement and connect it to terminals 3 + 4 at connector to control module.
- Start engine, and let run at idle.
- Measure voltage supply and observe display group 41, display field 2.
Htng.bef.cat.ON indicated: Specification: 11.0 to 14.5V
Htng.bef.cat.ON/Htng.bef.cat.OFF (alternating) indicated: Specification: oscillating between 0.0 and 12.0 V

If there is no voltage:
- Connect the multimeter to terminal 1 (engine ATW) terminal 3 (engines AUG, AWM) of the connector and to the engine Ground (GND) for a voltage measurement.
Specification: 11 to 15 V

If there is no voltage again:
- Check the wire connection from terminal 1 (engine ATW) terminal 3 (engines AUG, AWM) to Fuel Pump (FP) relay -J17- according to wiring diagram.

If voltage was approximately same as battery voltage:
- Switch ignition off.







- Connect VAG 1598/31 adapter cable to control module wiring harness. Engine Control Module (ECM) is not connected.







- Check wire between test box and 6-pin connector for open circuit according to wiring diagram. Terminal 4 + socket 5, wire resistance: max: 1.5 Ohms

If no malfunctions are found in wires:
- Replace Engine Control Module (ECM).