Sensor and Control Check
Heated Oxygen Sensor (HO2S) and oxygen sensor control behind Three Way Catalytic Converter (TWC), checking
- V.A.G 1551 scan tool (or VAG 1552 mobile scan tool) with VAG 1551/3B cable
- VAG 1598/31 adapter cable
- VAG 1788/10 RPM adjuster
- VAG 1526 multimeter or VAG 1715 multimeter
- VAG 1594 connector test kit
- Wiring diagram
Test requirements
- Exhaust system must be properly sealed between catalytic converter and cylinder head.
- Coolant temperature must be at least 85 °C, See display group 04, display field 3
Function test
- Connect V.A.G 1551 scan tool (VAG 1552). Start engine and select the Engine Control Module (ECM) using address word 01. (connecting scan tool and selecting ECM). Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks", Testing and Inspection
Indicated on display:
Rapid data transfer HELP
Select function XX
- Press buttons -0- and -8- to select "Read measuring value block" function 08. Press -Q- button to confirm input.
Indicated on display:
Read measuring value block
Enter display group number XXX
- Press buttons -0-, -3- and -4- to select "Display group number 34". Press -Q- button to confirm input.
Indicated on display: (1 to 4 - display fields)
Read measuring value block 34 ->
1 2 3 4
- Use VAG 1788/10 RPM adjuster to adjust engine RPM to between 1800 and 2200 RPM:
- Hold engine speed between 1800 and 2200 RPM until catalytic converter temperature in display field 2 rises to between 350 and 500 °C.
NOTE: This process can take a few minutes.
- Press -C- button.
Indicated on display:
Read measuring value block
Enter display group number XXX
- Press buttons -0-, -3- and -0- to select "Display group number 30". Press -Q- button to confirm input.
Indicated on display: (1 to 4 = display fields)
Read measuring value block 30 ->
1 2 3 4
- Check operational condition of oxygen sensor control behind catalytic converter (display field 2): Specification: x 1 x
NOTE: The bits in display fields 2 are only set to I after catalytic converter temperature has risen to above 350 °C (See display group 34, display field 2).
The sensor heater is pulsed by the Engine Control Module (ECM). This is why the indication for the sensor heater alternates between 0 and 1.
Explanation of 3-digit value in display field 2:
If oxygen sensor heater is not active:
- Test oxygen sensor heater after catalytic converter. Heater Check
If oxygen sensor or oxygen sensor control is not active:
- Check primary voltage.
NOTE: Oxygen sensor control is not active for engine code AWM.
If specified value is obtained:
- Press -C- button.
- Press buttons -0-, -3- and -6- to select "Display group number 36". Press -Q- button to confirm input.
Indicated on display: (1 to 4 = display fields)
Read measuring value block 36 ->
1 2 3 4
- Check oxygen sensor voltage behind catalytic converter in display field 1: Specification: 0.100 to 0.900 volts (may oscillate slightly)
If indication in display field 1 remains constant on one value:
- Continue testing according to the following table.
- Check diagnostic result in display field 2: Specification: B1-S2 OK
If "B1-S2 not OK" is displayed:
Checking primary voltage
- Disconnect 4-pin harness connector (brown) to Oxygen Sensor (O2S) behind Three Way Catalytic Converter (TWC) -G130- (item no.1).
- Use adapter cables from VAG 1594 to connect multimeter to terminals 3+4 (Motronic ECM connector) for voltage measurement.
- Start engine and measure primary voltage. Specification: 0.40 to 0.50 volts
- Switch ignition off.
If specified value is not obtained:
- Test oxygen sensor wires.
If specified value is obtained:
- Replace Oxygen Sensor (O2S) behind Three Way Catalytic Converter (TWC) -G130-.
Check oxygen sensor wiring for oxygen sensor 2
- Connect VAG 1598/31 adapter cable to control module wiring harness. Engine Control Module (ECM) is not connected.
- Check wires between test box and 4-pin connector to Motronic control module for open circuit according to wiring diagram.
Terminal 3 + socket 68
Terminal 4 + socket 69
Wire resistance: max: 1.5 Ohms
- Also check wires at 4-pin connector for short circuit to each other. Terminal 4 + socket 68, specification: Infinity Ohms
If no malfunctions are found in wires:
- Replace Engine Control Module (ECM).