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With Manufacturer's Scan Tool



Oxygen Sensor (O2S) and oxygen sensor control behind Three Way Catalytic Converter (TWC), checking

NOTE: Only gold plated contacts must be used to repair terminals 3 and 4 in the oxygen sensor harness connectors.

Special tools and equipment






- VAG 1788/10 engine speed adjuster
- VAG 1551 Scan Tool (ST) or VAG 1552 mobile scan tool with VAG 1551/3 adapter cable
- VAG 1598/22 test box
- Multimeter (Fluke 83 or equivalent)
- VW1594 adapter set
- Wiring diagram

Test requirements





- Fuse 43 OK
- Exhaust system between Three Way Catalytic Converter (TWC) and cylinder head free of leaks
- Coolant temperature at least 85 °C. See display group 04, display field 3

Functional check

- Press buttons -0- and -1- to insert "Engine Electronics" address word 01. When performing this step, engine must be running at idle (connecting scan tool and selecting engine electronics control module. [1][2]Reading and Clearing Diagnostic Trouble Codes

Indicated on display

Rapid data transfer HELP
Select function XX

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

Indicated on display

Read Measuring Value Block
Input display group number

- Press buttons -0-, -3-, and -4- to input display group number 34 (034) and press -Q- button to confirm input.

Indicated on display: (1-4 = display fields)

Read Measuring Value Block 34 ->
1 2 3 4

- Set engine speed at 2800-3200 RPM using VAG1788/10 engine speed adjuster.
- Maintain engine speed at 2800-3200 RPM until Three Way Catalytic Converter (TWC) temperature in display field 2 increases to above 352°C.

NOTE: This process can take a few minutes.

Display Group 34:






If the specified values are obtained:
- Set engine speed at 1800-2200 RPM using VAG1788/10 engine speed adjuster.
- Press -C- button.

Indicated on display

Read Measuring Value Block
Input display group number XXX

- Press buttons -0-, -3- and -0- to input display group number 30 (030) and press -Q- button to confirm input.

Indicated on display: (1-2 = display fields)

Read Measuring Value Block 30 ->
1 2

- Check status of oxygen sensor control after Three Way Catalytic Converter (TWC) (display field 2).

NOTE: The numbers in display field 2 will not be set to 1 until the Three Way Catalytic Converter (TWC) temperature has risen to above 352°C (see display group 34, display field 2).

Display Group 30:






Explanation of 3 digit number block in display field 2





If the specified value is obtained:
- Change to display group 37 as follows:
- Press -C- button.
- Press buttons -0-, -3- and -7- to input display group number 37 (037) and press -Q- button to confirm input.

Indicated on display: (1-4 = display fields)

Read Measuring Value Block 37 ->
1 2 3 4

- Check oxygen sensor voltage in display field 2.
- Check oxygen sensor control delay before Three Way Catalytic Converter (TWC) in display field 3.
- Check diagnosis result in display field 4.

Display Group 37:






NOTE:
A - Oxygen sensor voltage
B - Oxygen sensor control (Lambda regulation)






- The oxygen sensor control after the Three Way Catalytic Converter (TWC) is superior to the oxygen sensor control before Three Way Catalytic Converter (TWC) and is the regulation which makes corrections.
- Slight changes in the mixture are corrected (e.g. enriching) via the oxygen sensor before the Three Way Catalytic Converter (TWC) by holding the oxygen sensor control before Three Way Catalytic Converter (TWC) for a certain period (delay period) at the upper or the lower point. If the time is in the positive range (e.g. 50 ms), the mixture will be enriched. If it is in the negative range (e.g. -50 ms), the mixture will be leaned.
- If the delay period of the O2S control before the Three Way Catalytic Converter (TWC) increases to above 200 ms it is an indication that the exhaust system is leaking.

If the specified values are obtained:
- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06 and press -Q- button to confirm input.
- Turn off ignition.

Continuation

If B1-P2 OK appears in display field 4 and the value displayed in display field 3 is above 200 ms:
- Check exhaust system for leaks.

If B1-P2 OK appears in display field 4 and the value displayed in display field 3 is above 1200 ms:
- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06 and press -Q- button to confirm input.
- Perform test drive to remove possible residue on oxygen sensor and repeat check.

Observe the safety precautions when performing a road test. Technician Safety Information

If the specified values are still not obtained:
- Replace oxygen sensor behind Three Way Catalytic Converter (TWC) -G130-. Refer to item 34, Locations
- Check DTC memory. If necessary, repair any malfunctions and erase DTC memory.
Reading Diagnostic Trouble Codes
Clearing Diagnostic Trouble Codes

- Display readiness code. Monitors, Trips, Drive Cycles and Readiness Codes
If DTC memory has been erased or the Engine Control Module (ECM) was disconnected from permanent battery (B+) voltage, generate the readiness code again. Monitors, Trips, Drive Cycles and Readiness Codes

NOTE: If the oxygen sensor voltage is OK and the delay period for the oxygen sensor control after the Three Way Catalytic Converter (TWC) is still above 1200 ms even after a test drive, this points to an aged oxygen sensor before Three Way Catalytic Converter (TWC).

Evaluating display group 37, display field 2: Oxygen sensor voltage oxygen sensor after Three Way Catalytic Converter (TWC)





Possible causes of malfunction if O2S sensor control frequency is too slow:
- The slots or holes in O2S sensor body are blocked.
- The O2S sensor vent hole in area of connecting wire is blocked.
- The O2S sensor has been overheated (glazed).
- The O2S sensor has been damaged by leaded fuel.

Checking basic voltage for oxygen sensor 2





- Remove protective cover (arrows) and disconnect 4-pin harness connector (brown) -1- to oxygen sensor after Three Way Catalytic Converter (TWC) -G130-.






- Connect multimeter using auxiliary cables from VW1594 to measure voltage at terminals 3 + 4 (harness connector to Motronic Engine Control Module (ECM)).
- Start engine and measure basic voltage.
Specified value: 0.400-0.500 V
- Turn off ignition.

If the specified value is not obtained:
- Check oxygen sensor wiring.

If the specified value is obtained:
- Replace oxygen sensor behind Three Way Catalytic Converter (TWC) -G130-. Refer to item 34, Locations
- Check DTC memory. If necessary, repair any malfunctions and erase DTC memory.
Reading Diagnostic Trouble Codes
Clearing Diagnostic Trouble Codes

- Display readiness code. Monitors, Trips, Drive Cycles and Readiness Codes
If DTC memory has been erased or the Engine Control Module (ECM) was disconnected from permanent battery (B+) voltage, generate the readiness code again. Monitors, Trips, Drive Cycles and Readiness Codes

Checking oxygen sensor wiring, oxygen sensor 2
- Remove wiper arms and plenum chamber cover.






- Connect VAG1598/22 test box to control module wiring harness.






- Check wiring for open circuit between test box and 4-pin harness connector to Motronic Engine Control Module (ECM) according to wiring diagram.
- Terminal -3- + socket 51
- Terminal -4- + socket 52
Wire resistance: max. 1.5 ohms

- Check wiring at harness connector terminals -3- + -4- for short circuit to terminals -1- + -2- according to wiring diagram.
Specified value: Infinity ohms

- If no malfunction is found in the wiring, replace Engine Control Module (ECM).
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