With Manufacturer's Scan Tool
Oxygen Sensor And Oxygen Sensor Control Before Catalyst, Checking
NOTE: Only gold-plated contacts must be used to repair the contacts in the oxygen sensors connectors.
Special tools, test equipment and auxiliary items
- Scan tool VAG 1551 or vehicle system tester VAG 1552 with cable VAG 1551/3B
- Test box VAG 1598/31
- Multimeter (Fluke 83 or equivalent)
- Adapter set VAG 1594
- Wiring diagram
Check conditions
- Fuse 43 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 85 °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 idle speed. Connecting scan tool and selecting Engine Control Module (ECM). Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks/VAG 1551 Scan Tool", Testing and Inspection
Indicated on display
Rapid data transfer HELP
Select 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 (1-2 = Display zones)
Read measuring value block 30 ->
1 2
- Check the status of the oxygen sensor control before catalyst (display zone 1):
Display Group 30:
Significance of 3 digit number block in display zone 1
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 (1-2 = Display zones)
Read measuring value block 32 ->
1 2
- Check the oxygen sensor control learned value at idling (additive) in display zone 1.
- Check the oxygen sensor control learned value at part load (multiplicative) in display zone 2.
Display Group 32:
If the specification is obtained:
- Change to display group 33 as follows:
- VAG 1551: Press key 3
- VAG 1552: Press key (Up arrow)
Indicated on display (1-2 = Display zones)
Read measuring value block 33 ->
1 2
- Observe oxygen sensor control in display zone 1.
Display Group 33:
If the specification is obtained:
- Press -> key.
- Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.
- Switch off ignition.
Continuation
If the oxygen sensor control in display zone 1 does not fluctuate as stated:
- Press -> key.
- Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.
- 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.
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 %:
- Check the oxygen sensor before catalyst for aging. Oxygen Sensor Before Three-Way Catalytic Converter Aging, Check
Evaluating display zone 32, display zones 1 - oxygen sensor control learned values before catalyst
Possible causes of malfunction if probe control frequency is too slow:
- The slots or holes in probe body are blocked
- The probe vent hole in area of connecting wire is blocked
- The probe has been overheated (glazed)
- The probe has been damaged by leaded fuel
Checking oxygen sensor wiring for HO2S -G39-
- Remove inner plenum chamber cover, left:
- Connect test box VAG 1598/31 to control module wiring harness. The engine control module is not connected by this action.
- 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 wiring problem is detected:
- Replace oxygen sensor before catalyst (G39), item 13.
- Check DTC memory, if necessary, repair any malfunctions and then erase DTC memory, checking and erasing DTC memory. Refer to "Displaying, Reading and Erasing Trouble Codes/With Manufacturers Scan Tool/DTC Memory, Checking And Erasing", Testing and Inspection
- Read-out the readiness code. If the DTC memory has been erased or the engine control module was disconnected from permanent positive, the readiness code must be generated again.
Refer to "Monitors Trips and/or Drive Cycle/Displaying Readiness Code", Testing and Inspection
Refer to "Monitors Trips and/or Drive Cycle/Generating Readiness Code", Testing and Inspection