Sensor and Control Check

Special tools and equipment
- Scan tool VAG 1551 or vehicle system tester VAG 1552 with cable VAG 1551/3
- Test box VAG 1598/31
- Hand multimeter VAG 1526 or multimeter VAG 1715
- Adapter set VAG 1594
- Wiring diagram

Check conditions
- Exhaust system between catalyst and cylinder head must be free of leaks
- Coolant temperature must be at least 80 °C, See display group 04, display zone 3.

Functional check
- Connect scan tool VAG 1551 (VAG 1552). Start engine and select "Address word" 01 of engine control module. When doing this the engine must be running at idling speed.

(Connecting scan tool and selecting engine control module). Refer to "VAG 1551 Scan Tool" [1][2][3][4][5]Connecting VAG 1551 Scan Tool

Indicated on display:


Rapid data transfer HELP
Select function XX


- Press keys 0 and 8 for the function "Read measured value block" and confirm entry with Q key.

Indicated on display:


Read measured value block HELP
Input display group number XXX


- Press keys 0, 3 and 0 for the "Display group number 30" and confirm entry with Q key.

Indicated on display: (1-4 = Display zones)


Read measured value block 30 ->
1 2 3 4


- Check Oxygen sensor control status after catalyst (display zone 2):
Specification: 1 1 0


NOTE:
- The first position of the 3 digit number block fluctuates between 0 and 1 (heated oxygen sensor on and off).
- The third position of the 3 digit number block will be set to 1 only at increased exhaust temperature and part load.

Significance of 3 digit number block in display zone 1:







If the specification is not obtained:
- Check the heated oxygen sensor after catalyst. Checking

If the specification is obtained:
- Press C key.
- Press keys 0, 3 and 6 for "Display group number 36" and confirm entry with Q key.

Indicated on display: (1-4 = Display zones)


Read measured value block 36 ->
1 2 3 4


- Check Oxygen sensor voltage after catalyst in display zone 1:
Specification: 0.500 - 0.800 V (can fluctuate slightly)







If the display in display zone 1 remains constant:
- Continue check according to following table.
- Check diagnostic result in display zone 2:
Specification: B1-P2 OK


NOTE: It can take a few minutes until display jumps from "Test ON" to "B1-P2 OK".


If "B1-P2 nOK" is displayed::
- Press -> key.
- Interrogate fault memory. Refer to "Displaying, Reading and Erasing Trouble Codes" Testing and Inspection
- Carry out a test drive to remove possible residue on Oxygen sensor and repeat check.

Observe the valid safety precautions when carrying out a road test. Technician Safety Information

If the specifications are again not attained:
- Replace Oxygen sensor after catalyst (G130).

Checking basic voltage







- Remove protective cover (arrows) and separate 4-pin connector (brown) to Oxygen sensor after catalyst (G130).







- Connect multimeter with aux. cables from VAG 1594 to measure voltage at contacts 3 + 4 (connector to Motronic control module).
- Start engine and measure the basic voltage.
Specification: 0.40 - 0.50 V
- Switch off ignition.

If the specification is not obtained:
- Check Oxygen sensor wiring

If the specification is obtained:
- Replace Oxygen sensor 2 (G130).

Checking Oxygen sensor wiring, Oxygen sensor 2







- Connect test box VAG 1598/31 to control module wiring harness. The engine control module remains disconnected.







- Check wiring between test box and 4-pin connector to Motronic control module for open circuit using wiring diagram.
Contact 3 and socket 68
Contact 4 and socket 69
Wire resistance: max. 1.5 ohms
- Additionally check wiring at 4-pin connector for short to one another.
Contact 4 and socket 68
Specification: Infinity ohms

If no wiring fault is detected:
- Replace engine electronics control module.