With Generic Scan Tool
Oxygen sensor heater for oxygen sensors before Three Way Catalytic Converter (TWC), 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 see cylinder bank 1 in direction of travel, right; Bank 2 see cylinder bank 2 in direction of travel, left.
- When servicing terminals in harness connector of Heated Oxygen Sensor (HO2S), use only gold-plated terminals.
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 of the reservoir must be disconnected, and the bolt -arrow- of the coolant reservoir must be unscrewed and set 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 ... 10 Ohm
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 Measure to
Terminal
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 Measure to
Terminal
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. Text Box, Connecting For Wiring Test
- Check the following wire connections for open circuit according to wiring diagram:
- Oxygen Sensor (O2S) Heater -Z19- (bank 1, sensor 1):
Harness connector Test box
Terminal Socket
4 5
- Oxygen Sensor (O2S) Heater 2 -Z28- (bank 2, sensor 1):
Harness connector Test box
Terminal Socket
4 4
- Specified value: Wire resistance max 1.5 Ohm
- Also check wires for short circuit to B+ and 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, "Mode 3: Check DTC memory". Diagnostic Mode 3: Check DTC Memory
2 - If necessary, erase DTC memory, "Mode 4: Reset/erase diagnostic data". Diagnostic Mode 4: Check Reset/Erase Diagnostic Data
3 - Generate readiness code. Readiness Code, Generating
- End diagnosis and switch ignition off.