Oxygen Sensor (O2S) Heating, Checking

Oxygen Sensor (O2S) Heating, Checking

Location of harness connectors for HO2S and HO2S 2 (banks 1 and 2).







Location of harness connector for O2S behind TWC (bank 1): under right front carpet.







Location of harness connector for O2S 2 behind TWC (bank 2): under left front carpet.


NOTE: Heated oxygen sensor signals are monitored by the On Board Diagnostic (OBD) system.


- Connect VAG1551 or VAG1552 Scan Tool (ST), and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (engine running at idle). Refer "Scan Tool Testing/Scan Tool Connecting and Initial Checks/Connecting VAG1551 or VAG1552 Scan Tool" Testing and Inspection


Indicated on display


Rapid data transfer HELP
Select function XX


- Press buttons -0- and -8- to select "Read Measuring Value Block" function 08, and press -Q- button to confirm input.

Indicated on display


Read Measuring Value Block
Input display group number XXX


- Press buttons -0-, -2- and -8- to input display group number 28 (028), and press -Q- button to confirm input.

Indicated on display


Read Measuring Value Block 28 ->
1 2 3 4


- Check specified values for O2S heating (display fields 1-4):







- Press -> button to advance program sequence.
- Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input.

If O2S heating circuit malfunction is indicated:
- Disconnect oxygen sensor harness connector.







- Connect multimeter US 1119 (Fluke 83 or equivalent) and check for continuity (resistance) between harness connector terminals 1 and 2.
Specified value at room temperature: 2-10 ohms


NOTE: Wire resistance increases significantly at higher temperatures.


If there is an open circuit:
- Replace oxygen sensor.
- Check readiness code. If DTC memory has been erased, generate new readiness code.
Refer to "Monitors, Trips and/or Drive Cycle (Readiness Code)/Checking, Readiness Code" Testing and Inspection
Refer to "Monitors, Trips and/or Drive Cycle (Readiness Code)/Generating, Readiness Code" Testing and Inspection

If there is continuity:
- Check O2S heater circuit as follows.
- Check oxygen sensor fuses 3 and 4 at blue fuse panel located on right-side A-pillar.

If fuses are OK:







- Connect VAG1527B LED voltage tester between oxygen sensor harness connector terminal 1 and engine Ground.
- Briefly operate starter. (Do not operate starter for more than 2 minutes, to avoid storing malfunction in DTC memory)
LED must light up.

If LED does not light:







- Check wiring for open or short circuit between oxygen sensor harness connector terminal 1 and fuel pump relay.

If wiring and fuses are OK, but LED still does not light up:
- Check fuel pump relay. Testing and Inspection

If voltage supply is OK:
- Connect VAG1598/19 test box to Engine Control Module (ECM) harness connector. Refer "Scan Tool Testing/Scan Tool Connecting and Initial Checks/VAG1598/19 Test Box, Connecting" Testing and Inspection







- Check wiring for open or short circuits:
- Heated Oxygen Sensor (HO2S) -G39-
- Oxygen Sensor (O2S) heater -Z19-
- Heated Oxygen Sensor (HO2S) 2 -G108-
- Oxygen Sensor (O2S) 2 heater -Z28-

HO2S or HO2S 2 VAG1598/19 test box socket (ECM terminal)
connector terminal
2 (O2S heater -Z19-) E10
2 (O2S 2 heater -Z28-) E9







- Check wiring for open or short circuits:
- Oxygen Sensor (O2S) behind Three Way Catalytic Converter (TWC) -G130-
- Oxygen Sensor (O2S) heater -Z29-
- Oxygen Sensor (O2S) 2 behind Three Way Catalytic Converter (TWC) -G131-
- Oxygen Sensor (O2S) 2 heater -Z30-

O2S behind TWC VAG1598/19 test box socket (ECM terminal)
connector terminal
2 (O2S heater -Z29-) E4
2 (O2S 2 heater -Z30-) E8







- If there are no open or short circuits, replace Engine Control Module (ECM).