Oxygen Sensors and Control Before Catalytic Converter, Checking
Oxygen Sensors and Control before Catalytic Converter, Checking
Special tools, testers and auxiliary items required
• (VAG1526A)
• (VAG1594A)
• (VAG1598/31)
• (VAS5051) with (VAS5051/1)
Test requirements
• No leaks in exhaust system
• Engine coolant temperature at least 80 °C => display group 004, display zone 3.
Test sequence
- Connect vehicle diagnostic, testing and information system (VAS5051) and select vehicle system "01 -Engine electronics" in selection. Refer to => [ VAS 5051, Connecting and Select Functions ] VAS 5051, Connecting and Select Functions. 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):
- Check specifications in display zones - 1 - and - 3 -.
• By increasing the engine speed the specified values are achieved quickly.
• The "oxygen sensor status" indicates the condition of the oxygen sensor control and the oxygen sensors.
• The first digit of the 3-digit display (heating) fluctuates between 0 and 1.
Display on (VAS5051):
- Only continue with test if displays have reached "111" in display zones - 1 - and - 3 - at least once.
- Press arrow button.
Checking oxygen sensor learned values and oxygen sensor control
Display on (VAS5051):
1. Enter display group
- Enter "032" for "display group number 032" in zone - 2 - and confirm entry by pressing Q button.
- Check values in display zones - 1 - to - 4 -.
- Press arrow button.
Display on (VAS5051):
1. Enter display group
- Enter "033" for "display group number 033" in zone - 2 - and confirm entry by pressing Q button.
Display on (VAS5051):
- Activate basic setting by pressing - A - button.
- Check indication in display fields - 1 - to - 4 -.
Note on display zones 2 and 4:
Displayed is the oxygen sensor voltage signal which was prepared and smoothed in the engine control module. 1.5 V in the display corresponds to oxygen sensor 1 (with the engine at operating temperature without secondary air system influence).
- Exit function "04 - Basic setting" by pressing arrow button.
continuation
If specification is not obtained in display zone 1 or display zone 3, or if the value does not fluctuate by at least 2%:
- Perform drive test to free oxygen sensors from any possible residues and repeat test.
If the specified result is not achieved in display zones 1 or 3, or if the value does not fluctuate by at least 2%, even after the test drive:
- Check basic voltage.
- Check oxygen sensor heating before catalytic converter. Refer to => [ Oxygen Sensors before Catalytic Converter, Checking Heating ] Oxygen Sensors Before Catalytic Converter, Checking Heating.
- Check oxygen sensor before catalytic converter for aging. Refer to => [ Oxygen Sensors before Catalytic Converter, Checking Aging ] Oxygen Sensors Before Catalytic Converter, Checking Aging.
Evaluating display group 032
Evaluating display group 032
Evaluating display group 033
Checking basic voltage
Test requirements:
• Fuse for oxygen sensors OK. Refer to
- Disconnect 6-pin connector of relevant oxygen sensor before catalytic converter => [ Identification of connector bracket - right
side of vehicle ] Locations and => [ Identification of connector bracket - left side
of vehicle ] Locations
- Connect multimeter between terminals 1 and 5 to measure voltage.
- Switch ignition on.
• Specified value: 0.400 to 0.500 V
- Switch ignition off.
If specified value is not obtained:
- Check oxygen sensor wiring:
Bank 1 , or Bank 2
If specified value is obtained:
- Replace relevant oxygen sensor before catalytic converter.
Check oxygen sensor wiring, bank 1, sensor 1, Heated Oxygen Sensor
- Disconnect 6-pin connector of bank 1, Heated Oxygen Sensor (HO2S) (G39) => [ Identification of connector bracket - right
side of vehicle ] Locations
- Connect test box (VAG1598/31) to wiring harness for engine control module; engine control module must not be connected. Refer to => [ Wiring and Component Check with Test Box VAG 1598/31 ] Wiring and Component Check With Test Box VAG 1598/31.
- Test for open circuit in following wiring connections.
- Repair open circuit, if necessary.
- Check for shorts between two wires.
If no wiring malfunction is detected:
- Replace engine control module:
• With anti-theft housing. Refer to => [ Engine Control Module with Metal Anti-Theft Housing ] Engine Control Module With Metal Anti-Theft Housing.
• Without anti-theft housing. Refer to => [ Engine Control Module without Metal Anti-Theft Housing ] Engine Control Module Without Metal Anti-Theft Housing.
Check oxygen sensor wiring, bank 2, sensor 1, Heated Oxygen Sensor 2
- Disconnect 6-pin connector of bank 2, Heated Oxygen Sensor (HO2S) 2 (G108) => [ Identification of connector bracket - left side
of vehicle ] Locations.
- Connect test box (VAG1598/31) to wiring harness for engine control module; engine control module must not be connected. Refer to => [ Wiring and Component Check with Test Box VAG 1598/31 ] Wiring and Component Check With Test Box VAG 1598/31.
- Test for open circuit in following wiring connections.
- Repair open circuit, if necessary.
- Check for shorts between two wires.
If no wiring malfunction is detected:
- Replace engine control module:
• With anti-theft housing. Refer to => [ Engine Control Module with Metal Anti-Theft Housing ] Engine Control Module With Metal Anti-Theft Housing.
• Without anti-theft housing. Refer to => [ Engine Control Module without Metal Anti-Theft Housing ] Engine Control Module Without Metal Anti-Theft Housing.