With Generic Scan Tool
Oxygen Sensor (O2S) and oxygen sensor control before Three Way Catalytic Converter (TWC), checking
NOTE: When servicing terminals in harness connector of Heated Oxygen Sensor (HO2S), use only goldplated terminals.
Recommended special tools and equipment
- V.A.G 1526 multimeter or V.A.G 1715 multimeter
- V.A.G 1594 Connector test set
- Wiring diagram
Test requirements
- The respective fuses of Heated Oxygen Sensor (HO2S) -G39- and Heated Oxygen Sensor (HO2S) 2 -G108- must be OK:
- Battery voltage must be at least 11.5 volts.
- All electrical consumers like, for example, lights and rear window heating must be switched off.
- Parking brake must be engaged or else daylight driving lights will be switched on.
- If vehicle is equipped with an A/C system, it must be switched off.
- Ground (GND) connections between engine and chassis must be OK.
- Exhaust system must be properly sealed between catalytic converter and cylinder head.
- Coolant temperature must be at least 80°C, Diagnostic mode 1: Check measuring values; PID 5, Coolant temperature. Refer to "Scan Tool Testing/Diagnostic Mode 1: Check Measuring Values". Diagnostic Mode 1: Check Measuring Values
- Oxygen sensor heaters for oxygen sensors before catalytic converter must be OK, Oxygen Sensor Heater For Oxygen Sensors Before Catalytic Converter, Checking
Function test
- Select the following output of oxygen sensor signals and check whether the specified values are being reached, Diagnostic mode 5: Check output of oxygen sensor signals. Refer to "Scan Tool Testing/Diagnostic Mode 5: Check Output of Oxygen Sensor Signals" Diagnostic Mode 5: Check Output of Oxygen Sensor Signals
- Check the specified values of the output of oxygen sensor signals at idle:
*) V = Voltage in Volts (oxygen sensor signal)
**) t = Time in seconds
Vehicles with engine code AHA
Vehicles with engine code ATQ
Continuation for all vehicles
NOTE:
- Cylinder bank 1 = in driving direction, right
- Cylinder bank 2 = in driving direction, left
If specified values are obtained:
- End diagnosis and switch ignition off.
If specified values are not obtained:
- End diagnosis and let engine continue to run at idle.
- Check primary voltage.
Checking primary voltage
- Disconnect 4-pin harness connector to the respective oxygen sensor:
- Heated Oxygen Sensor (HO2S) -G39-, bank 1 4-pin harness connector (black, arrow).
- Heated Oxygen Sensor (HO2S) 2 -G108-, bank 2 4-pin harness connector (black, arrow).
NOTE: To reach this harness connector, remove coolant reservoir attachment screws and tilt coolant reservoir to the side. The coolant hoses remain connected.
- Connect multimeter for voltage measurement to terminals 3 + 4 of the respective connector to Engine Control Module (ECM) and measure primary voltage.
Specified value: 0.40 to 0.50 volts
- Switch ignition off.
If specified value is not obtained on one or both Heated Oxygen Sensors (HO2S):
- Test oxygen sensor wires.
If specified values are obtained:
- Replace the respective oxygen sensor:
- Heated Oxygen Sensor (HO2S) -G39-, bank 1, item 1
- Heated Oxygen Sensor (HO2S) 2 -G108-, bank 2, item 15
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code. Refer to "Monitors, Trips and/or Drive Cycle/Readiness Code, Generating". Monitors, Trips, Drive Cycles and Readiness Codes
Checking oxygen sensor wires
- Connect test box to control module wiring harness, connect test box for wiring test. Refer to "Scan Tool Connecting/Test Box, Connecting For Wiring Test". Test Box, Connecting For Wiring Test
- Check wires between test box and 4-pin connector to Engine Control Module (ECM) for open circuit according to wiring diagram.
Wire resistance: max: 1.5 Ohms
Vehicles with engine code AHA
Vehicles with engine code ATQ
Continuation for all vehicles
- Also check wires for short circuit to B+ or Ground (GND).
Specified value: Infinity Ohms
If no malfunctions are found in wires:
- Replace Motronic Engine Control Module (ECM) -J220-.