Oxygen Sensor Heater For Oxygen Sensor Before Three Way Catalytic Converter (TWC), Checking

Oxygen Sensor Heater For Oxygen Sensor Before Three Way Catalytic Converter (TWC), Checking

NOTE: Use only gold-plated terminals when servicing terminals in the harness connector.

Recommended special tools and equipment
- V.A.G1526 multimeter or V.A.G1715 multimeter
- V.A.G1594 connector test kit
- Wiring diagram

Test requirements







- Corresponding fuses on E-box in engine compartment, left side, of Oxygen Sensor (O2S) Heater -Z19- for Heated Oxygen Sensor (HO2S) -G39- must be OK:

NOTE: Fuses on this fuse holder are labelled "SB" in the wiring diagram.

- Engine Component Power Supply Relay -J757-, relay position R3, must be OK, check:
- Ground (GND) connections between engine and chassis must be OK.
- Ignition switched off.

Test sequence
Observe safety precautions.
Observe rules for cleanliness.







- Disconnect black 6-pin harness connector -arrow- to Heated Oxygen Sensor (HO2S) G39-.

Checking resistance

NOTE: For resistance testing of sensor heating, oxygen sensor should be cooled to ambient temperature. High temperatures at oxygen sensor may lead to inaccurate measurements.







- Check resistance for sensor heater at connector to oxygen sensor terminal 3 and 4.

Specified value: smaller than 20.0 Ohms

If specified value is not obtained:
- Replace Heated Oxygen Sensor (HO2S) -G39- before catalytic converter, item 2.
- Erase DTC memory of Engine Control Module (ECM). Diagnostic Mode 04 - Erase DTC Memory
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

If specified value is obtained:
- Check wires to Engine Control Module (ECM) according to wiring diagram.

Checking wires to Engine Control Module (ECM)
- Connect test box to 94-pin connector of wiring harness. Test Box, Connecting For Wiring Test

Engine Control Module (ECM) is not connected.







- Check wire between test box and 6-pin connector to Engine Control Module (ECM) for open circuit according to wiring diagram.

Terminal 3 + socket 51

Wire resistance: max. 3.0 Ohms

- Check the wire for short circuit to B+ and to Ground (GND).

Specified value: Infinity Ohms

- Check wire between 6-pin connector terminal 4 and Engine Component Power Supply Relay -J757- for open circuit according to wiring diagram.

Wire resistance: max. 3.0 Ohms

- Erase DTC memory of Engine Control Module (ECM). Diagnostic Mode 04 - Erase DTC Memory
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

If no malfunctions are found in wires:
- Replace Engine Control Module (ECM) -J623-.