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Sensor and Sensor Control Check



Oxygen Sensors And Oxygen Sensor Control Behind Catalytic Converter, Checking


NOTE: The oxygen sensor before catalytic converter (bank 1, sensor 1 and bank 2, sensor 1) regulates to oxygen sensor 1. If this oxygen sensor is damaged, e.g. due to soiling or overheating, the regulation value may have shifted. Deviations from oxygen sensor 1 are detected by the oxygen sensor behind catalytic converter (bank 1, sensor 2 and bank 2, sensor 2). If it recognizes the deviations downward or upward, it influences the regulation before catalytic converter, generally increasing or decreasing it respectively.







Special tools and equipment
- VAG 1526A
- VAG 1594A
- VAG 1598/31
- VAS5051 with VAS5051/1

Test requirements:
- No leaks in exhaust system
- Coolant temperature at least 80 degree C, see display group 004, display zone 3.

Test sequence
- Connect vehicle diagnostic, testing and information system VAS5051 and select vehicle system "01 -Engine electronics". Connecting VAS 5051 Scan Tool
Engine must be running at idling speed.

Display on VAS5051:







- Under -1 - select diagnostic function "04 - Basic setting".

Display on VAS5051:







1 - Enter display group
- Enter "030" for "display group number 030" in zone -2- and confirm entry by pressing -Q- button.

Display on VAS5051:







- Activate basic setting by pressing -A- button.
- Check specifications in display zones -2- and -4-.

NOTE:
- By increasing the engine speed the specified values are achieved quickly.
- The "heated oxygen sensor (HO2S) status" indicates the condition of the oxygen sensor (O2S) control and the heated oxygen sensor (HO2S).


Display Group 030:






Significance of 3-digit readout of display group 030







NOTE:
- The first digit of the 3-digit display (heating) fluctuates between 0 and 1.
- The oxygen sensor (O2S) control for heated oxygen sensor (HO2S) after catalytic converter (bank 1, sensor 2 and bank 2, sensor 2) is not active without engine load, i.e. the last digit of the 3-digit display is 0.

Display on VAS5051:







- Continue with test if displays have reached "110" in display zones -2- and -4- at least once.
- Press <- button.

Checking oxygen sensor (O2S) control behind catalytic converter

Display on VAS5051:







1 - Enter display group max. input value = 255
- Enter "037" for "display group number 037" in zone -2- and confirm entry by pressing -Q- button.

Display on VAS5051:







- Activate basic setting by pressing -A- button.
- Check heated oxygen sensor (HO2S) voltage in display zone -2-.
- Check oxygen sensor (O2S) correction value in display zone-3- and diagnosis result in display zone -4-.


Display Group 037:






- Press <- button.

Display on VAS5051:







1 - Enter display group
- Enter "038" for "display group number 038" in zone -2- and confirm entry by pressing -Q- button.

Display on VAS5051:







- Activate basic setting by pressing -A- button.
- Check heated oxygen sensor (HO2S) voltage in display zone -2-.
- Check oxygen sensor correction value in display zone-3- and diagnosis result in display zone -4-.


Display Group 038:






- Exit function "04 - Basic setting" by pressing <- button.

Evaluation of display groups 037 and 038


Display Zone 2:






Continued

If specification in display zone 3 or 4 is not obtained:
- Perform test drive to free heated oxygen sensor (HO2S) from any possible residues and repeat test.

If specified value in display zone 3 or 4 is not obtained, even after a test drive has been performed:
- Replace relevant heated oxygen sensor (HO2S) 1 before catalytic converter.

NOTE: If the heated oxygen sensor (HO2S) voltage is OK and after a road test the oxygen sensor correction value is still outside the specification, this indicates aging of the heated oxygen sensor (HO2S) before the catalytic converter.

Checking basic voltage
- Disconnect 4-pin connector of relevant heated oxygen sensor (HO2S) behind catalytic converter.







- Connect multimeter between terminals 3 and 4 to measure voltage.
- Switch ignition on.
- Specified value: 0.400 to 0.500 V
- Switch ignition off.

If specified value is not obtained:
- Check heated oxygen sensor (HO2S) Bank 1 wiring or Bank 2.

If specified value is obtained:
- Replace relevant heated oxygen sensor (HO2S) behind catalytic converter.

Checking heated oxygen sensor (HO2S) wiring, bank 1 Oxygen Sensor (O2S) Behind Three Way Catalytic converter (TWC) -G130-

- Disconnect 4-pin connector, bank 1, oxygen sensor (O2S) behind three way catalytic converter (TWC) -G130-.
- Connect test box VAG 1598/31 to wiring harness for engine control module; do not connect engine control module. Wiring and Component Testing Using VAG1598/31 Test Box
- Test for open circuit in following wiring connections.

Connector Test box VAG 1598/31
terminal Socket
3 68
4 69

- Repair open circuit, if necessary.
- Check for shorts between two lines.

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

Checking heated oxygen sensor (HO2S) wiring, bank 2 Oxygen Sensor (O2S) 2 Behind Three Way Catalytic Converter (TWC) -G131-

- Disconnect 4-pin connector, bank 2, oxygen sensor (O2S) 2 behind three way catalytic converter (TWC) -G131-.
- Connect test box VAG 1598/31 to wiring harness for engine control module; do not connect engine control module. Wiring and Component Testing Using VAG1598/31 Test Box
- Test for open circuit in the following wiring connections.

Connector Test box VAG 1598/31
terminal Socket
3 10
4 11

- Repair open circuit, if necessary.
- Check for shorts between two lines.

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