With Generic Scan Tool

Oxygen Sensor (O2S) Heater -Z19- Before Catalytic Converter, Checking

Recommended special tools and equipment







- VAG1526A hand multimeter
- VAG1594A connector test kit
- VAG1598/31 test box

Test requirements:
- Fuse for oxygen sensor heater OK
- Ground (GND) connections at engine and transmission OK
- Fuel Pump (FP) Relay OK; checking. Testing and Inspection
- Ignition switched off.


NOTE:
- Voltage is supplied to Oxygen Sensor (O2S) Heater -Z19- via the Fuel Pump (FP) relay.
- When servicing terminals in harness connector of Heated Oxygen Sensor (HO2S), use only gold-plated terminals.


Work procedure







- Disconnect 6-pin harness connector (black) -5- to Heated Oxygen Sensor (HO2S) -G39- before catalytic converter.







NOTE: Coolant reservoir screw (arrow) must be removed and coolant reservoir must be placed to the side in order to access harness connector. The coolant hoses remain connected.







- Connect multimeter between terminal 3 and 4 for resistance measurement.
- Specified value at room temperature: 2,5 ... 10 Ohm

If specified value is not obtained:
- Replace Heated Oxygen Sensor (HO2S) -G39-.

Checking internal resistance







- Connect multimeter between terminal 3 and 4 for resistance measurement.
- Specified value at room temperature: 2,5 ... 10 Ohm

If specified value is not obtained:
- Replace oxygen sensor before catalytic converter.

If specified value is obtained:

Checking voltage supply







- Connect multimeter between terminal 3 and 4 for voltage measurement.
- Operate starter briefly.
- Specified value: approx. battery voltage

- Switch ignition off.

If there is no voltage:
- Connect multimeter for voltage measurement as follows:

Harness connector Terminal Measure to
3 Engine Ground (GND)

- Operate starter briefly.
- Specified value: approx. battery voltage

- Switch ignition off.

If there is no voltage again:
- Check wire connection from harness connector terminal 3 to Fuel Pump (FP) Relay -J17- via fuse for open circuit according to wiring diagram.
- Specified value: Wire resistance max 1.5 Ohm

- If necessary, repair wire connection.

If voltage supply is OK:

Check Ground (GND) activation







- Connect multimeter for voltage measurement as follows:


Harness connector Terminal Measure to
4 B+

- Operate starter briefly.
- Specified value: approx. battery voltage

- Switch ignition off.

If specified value is not obtained:
- Connect test box to wiring harness of Engine Control Module (ECM); ECM is not connected. Test Box, Connecting For Wiring Test







- Check the following wire connections for open circuit according to wiring diagram:

Harness connector Terminal Test box Socket
4 5

- Specified value: Wire resistance max 1.5 Ohm

- Also check wires for short circuit to B+ and Ground (GND).
- Specified value: Infinite Ohm (no continuity)

- If necessary, repair wire connection.

If no malfunctions are detected:
- Replace Engine Control Module (ECM).

Final procedures
After repair work, the following work steps must be performed in the mentioned sequence:
1 - Check DTC memory, see "Mode 3: Check DTC memory". Diagnostic Mode 3: Check DTC Memory
2 - If necessary, erase DTC memory, see "Mode 4: Reset/erase diagnostic data". Diagnostic Mode 4: Reset/Erase Diagnostic Data
3 - Generate readiness code. Readiness Code, Generating

- End diagnosis and switch ignition off.