Oxygen Sensor Heating, Before TWC

Special tools, testers and auxiliary items:
- VAG 1551/1552 scan tool with VAG 1551/3 adapter cable.
- VAG 1598/18 test box.
- Multimeter (Fluke 83 or equivalent).
- Connector test kit VW 1594.
- Wiring diagram.

Test conditions:
- Fuse 18 OK.

Test sequence:
- Engine running at idle.
- Connect VAG 1551/1552 scan tool and select "Engine Electronics" address word 01. Testing and Inspection




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




Indicated on display
- Press buttons -1-, -2- and -0- to input display group 120 and press -Q- button to confirm input.




Indicated on display (1-4 = Display fields)
- Check the resistance value for O2S heating before three way catalytic converter (display field 3).





- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06 and press -Q- button to confirm input.
- Switch ignition off.

Relevance of values in 8-digit number block




Continuation:





- Disconnect 4-pin connector -1- (black) to HO2S -G39- (before three way catalytic converter).





- Connect multimeter with test leads from VW 1594 to measure resistance at HO2S connector terminals 1 and 2.
- Check the resistance value.
Specification: 0.0-24.2 ohms .

If the specification is not attained:
- Replace HO2S -G39- (before three way catalytic converter).

If the specification is attained:
Relevance of values in 8-digit number block




- Check relevance table for value of O2S control status, display group 120, display field 4, 1st position from left.
- Set multimeter to voltage measurement range.





- Connect multimeter using test leads from VW 1594 to measure voltage at ECM connector terminals 1 and 2.
- Measure the voltage supply.
When display = 1: specification is 11.0-14.5 volts.
When display = alternately 0 and 1: specification is fluctuating between 0.0-12.0 volts.

If no voltage is present:





- Connect multimeter with test leads from VW 1594 to measure voltage at ECM connector terminal 1 and vehicle Ground (GND).
Specification: 11.0-14.5 volts.

If again no voltage is present:
- Check wiring from terminal 1 to relay panel according to wiring diagram.

If voltage was present:
Relevance of values in 8-digit number block



- Check relevance table for value of O2S control status, display group 120, display field 4, 1st position from left.





- Connect multimeter using test leads from VW 1594 to ECM connector terminal 2 and battery positive (B+).
When display = 1: specification is 11.0-14.5 volts.
When display = alternately 0 and 1: specification is fluctuating between 0.0-12.0 volts.
- Switch ignition off.

If no voltage is present:





- Connect VAG 1598/18 test box to ECM wiring harness (arrow).





- Check wiring between test box and 4-pin connector for open circuit according to wiring diagram.
Terminal 2 and test box socket 12.
Resistance: max. 1.5 ohms.

If no wiring malfunction is detected:
- Replace Engine Control Module (ECM) -J220-.
- Read the readiness code. If DTC memory has been erased, verify repair via appropriate display group See Readiness code, creating. Testing and Inspection