Oxygen Sensor Heater For Oxygen Sensors Before Catalytic Converter, Checking

Oxygen Sensor Heater For Oxygen Sensors Before Catalytic Converter, Checking







Recommended special tools and equipment
- VAG1526A multimeter
- VAG1594A connector test kit
- VAG1598/31 test box

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

NOTE:
- Voltage for Oxygen Sensor (O2S) Heater -Z19- (bank 1, sensor 1) and Oxygen Sensor (O2S) 2 Heater 2 -Z28- (bank 2, sensor 1) is supplied via the Fuel Pump (FP) relay.
- Bank 1 = cylinder bank 1 in direction of travel, right; Bank 2 = cylinder bank 2 in direction of travel, left.
- When servicing terminals in harness connector of oxygen sensor, use only gold-plated terminals.

Work procedure







- Disconnect electrical 6-pin harness connector -1- from Heated Oxygen Sensor (HO2S) - G39- (before catalytic converter) and Oxygen Sensor (O2S) Heater -Z19- (bank 1, sensor 1).







- Disconnect electrical 6-pin harness connector -4- from Heated Oxygen Sensor (HO2S) - G108- (before catalytic converter) and Oxygen Sensor (O2S) 2 Heater 2 -Z28- (bank 2, sensor 1).







NOTE: To reach the harness connectors, the left cover in engine compartment must be removed, the line to Engine Coolant Level (ECL) Warning Switch at bottom on reservoir must be disconnected, bolt (arrow) of coolant reservoir must be removed and set it aside. Coolant hoses -1- to -3- remain connected.

Checking internal resistance







- Connect multimeter between terminal 3 and 4 for resistance measurement.
- Specified value at room temperature: 2.5 to 10 Ohms

If specified value is not obtained:
- Replace respective 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 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 Ohms
- 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.







- Check the following wire connections for open circuit according to wiring diagram:
- Oxygen Sensor (O2S) Heater -Z19- (bank 1, sensor 1):

Harness connector Terminal Test box Socket
4 5

- Oxygen Sensor (O2S) Heater 2 -Z28- (bank 2, sensor 1):

Harness connector Terminal Test box Socket
4 4

- Specified value: Wire resistance max 1.5 Ohms
- Check wires for short circuit to B+ and to Ground (GND).

- Specified value: Infinity 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. Diagnostic Mode 03 - Read DTC Memory
2. If necessary, erase DTC memory. Diagnostic Mode 04 - Erase DTC Memory
3. If DTC memory was erased, generate readiness code.

- End diagnosis and switch ignition off.