With Manufacturer's Scan Tool
Oxygen Sensor and Oxygen Sensor Control Before Catalyst, Checking
NOTE:
- Raise vehicle to reach Oxygen sensor connector.
- The Oxygen sensor (before catalyst) has constant regulation and can be distinguished by a 6-pin connector from the Oxygen sensor after catalyst.
- Only gold contacts may be used for servicing the contacts in the connector for the Oxygen sensor.
Special tools and equipment
- V.A.G 1551 scan tool or 1552 scan tool with cable VAG1551/3
- Test box VAG1598/31
- Hand multimeter VAG 1526 or multimeter VAG 1715
- Adapter set VAG 1594
- Wiring diagram
Check conditions
- All fuses must be OK.
- The battery voltage must be at least 11.5 V.
- 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 V.A.G 1551 scan tool ((VAG 1552). Start engine and select "Address word" 01 of engine control module. Engine must be running at idling speed. [1][2]Reading and Clearing Diagnostic Trouble Codes
Indicated on display:
Rapid data transfer HELP
Self function XX
- Press keys 0 and 8 for the function "Read measuring value block" and confirm entry with Q key.
Indicated on display:
Read measuring value block
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 to 2 = Display zones)
Read measuring value block 30 ->
1 2
- Check Oxygen sensor control status before catalyst (display zone 1):
Specification: 111
Significance of 3 digit number block in display zone 1:
NOTE: The first position of the 3 digit number block fluctuates between 0 and 1 (Oxygen sensor heating on and off).
If the specification is not obtained:
- Check the Oxygen sensor heating before catalyst. Oxygen Sensor Heater For Oxygen Sensor Before Three Way Catalytic Converter (TWC), Checking
If the specification is obtained:
- Change to display group 32 as follows:
- Press C key.
- Press keys 0, 3 and 2 for "Display group number 32" and confirm entry with Q key.
Indicated on display: (1 to 2 = Display zones)
Read measuring value block 32 ->
1 2
- Check Oxygen sensor learned values at idling speed (additive) in display zone 1.
Specification: -10.0 to 10.0%
- Check Oxygen sensor learned values at part load (multiplicative) in display zone 2.
Specification: -10.0 to 10.0%
If the specification is not obtained:
- Evaluating display group 32. Display Groups 30-49, 99, 107 (Oxygen Sensor Control)
If the specification is obtained:
- Change to display group 33 as follows:
V.A.G 1551: Press key 3
VAG 1552: Press key (up arrow)
Indicated on display: (1 to 2 = Display zones)
Read measuring value block 33 ->
1 2
- Observe Oxygen sensor control in display zone 1. The display must fluctuate at least 2 % in the range -10.0 to 10%.
If the Oxygen sensor control in display zone 1 does not fluctuate as stated:
- Press -> key.
- Press keys 0 and 6 for the "End data transfer" function and confirm input with the Q key.
- Switch off ignition.
- Road test vehicle to burn Oxygen sensors clean and repeat check.
Observe the valid safety precautions when carrying out a road test.
If the the specifications in display zone 1 are not obtained even after a test drive, or the value does not fluctuate by at least 2%:
- Replace the Oxygen sensor before catalyst -G39-.
- Check DTC memory, if necessary, repair any faults and then erase DTC memory.
Reading Diagnostic Trouble Codes
Clearing Diagnostic Trouble Codes
Checking Oxygen sensor wiring
- Remove wiper arms and cowl panel:
- Connect test box VAG1598/31 to control module wiring harness. The engine control module remains disconnected.
- Remove protective cover -arrows- and separate 6-pin connector (black) -1- to Oxygen sensor before catalyst -G39-.
- Check wiring for open circuit between test box and 6-pin connector (to control module) according to wiring diagram.
Contact 1 + socket 70
Contact 2 + socket 71
Contact 5 + socket 51
Contact 6 + socket 52
Wire resistance: Max 1.5 Ohms
- Additionally check wires all for short to one another.
Specification: Infinity Ohms
If no malfunction is detected in the pipes:
- Replace Heated Oxygen sensor (HO2S) -G39-.
- Check DTC memory, if necessary, repair any malfunctions and then erase DTC memory.
Reading Diagnostic Trouble Codes
Clearing Diagnostic Trouble Codes