With Manufacturer's Scan Tool

Oxygen Sensor Heater For Heated Oxygen Sensors (HO2S) Before Catalytic Converter, Checking

When servicing terminals in harness connector of Heated Oxygen Sensor (HO2S), use only gold-plated terminals.

Special tools and equipment
- V.A.G 1551 Scan Tool (or VAG 1552 mobile scan tool) with VAG 1551/3 cable
- VAG 1598/31 test box
- 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 working properly.

Test Sequence

- Connect V.A.G 1551 scan tool (VAG 1552). Start engine and select the Engine Control Module (ECM) using address word 01. Refer to Scan Tool Testing/Scan Tool Connecting and Initial Checks/Connecting V.A.G 1551 Scan Tool [1][2][3]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
Input display group number XXX

- Press 0, 3 and 0 for function "display group number 30", and then press Q to exit from input mode.

Indicated on display (1 - 4 = display fields)

Read Measuring Value Block 30 ->
1 2 3 4

- Check the status of oxygen sensor heater in display fields 1 and 3:
Specification: 111

011 also briefly, since the oxygen sensor heater is clocked. Evaluating measuring value blocks. Refer to Scan Tool Testing/Measuring Value Blocks (Function 08)/Evaluating Display Groups 30-44, 99 Display Groups 30-44, 99 (Oxygen Sensor Control)

If specified value is not obtained:
- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06. Press -Q- button to confirm input.
- Switch ignition off.
- Unplug 4-pin harness connector going to corresponding Heated Oxygen Sensor (HO2S):






Heated Oxygen Sensor (HO2S) (G39), bank 1 before catalytic converter 4-pin harness connector (black) (arrow).






Heated Oxygen Sensor (HO2S) 2 (G108), bank 2 before catalytic converter 4-pin harness connector (black) (arrow).






- Check oxygen sensor heater on connector to Heated Oxygen Sensor (HO2S) terminals 1 + 2 for continuity
Specification: max. 200 Ohms

If specified value is not obtained:
- Replace appropriate Heated Oxygen Sensor (HO2S).
- Cylinder bank 1 (G39) item 27
- Cylinder bank 2 (G108) item 18

If expected value is not obtained:
- Check Ground (GND) connection of the appropriate oxygen sensor heater.
- Switch ignition off.






- Connect VAG1598/31 test box to control module wiring harness. Engine Control Module (ECM) is not connected.






- Check wire connection of terminal 2 of appropriate connector of Heated Oxygen Sensor (HO2S) for continuity to test box.
Specification: max. 1.5 Ohms

Connector to Heated Oxygen Sensor VAG 1598/31 test box socket
(HO2S) -G39-, bank 1 before
catalytic converter terminal
2 5

Connector to Heated Oxygen Sensor VAG 1598/31 test box socket
(HO2S) 2 -G108-, bank 2 before
catalytic converter terminal
2 4

If expected value is not obtained:
- Switch ignition on.
- Bridge sockets 2 + 65 of test box using auxiliary wires from VAG 1594. Transfer Fuel Pump (FP) must be running.






- Connect multimeter to terminals 1 + 2 of appropriate connector to make voltage measurement.
Specification: at least 11.5 V

If there is no voltage:
- Switch ignition off.
- Check wire connection from terminal 1 to Fuel Pump (FP) relay (J17) (see wiring diagram).

If voltage supply and wires are in order:
- Replace Engine Control Module (ECM).
- Read readiness code. If DTC memory was erased or Engine Control Module (ECM) was disconnected from continuous B+ supply, readiness code must be re-generated. Monitors, Trips, Drive Cycles and Readiness Codes