Oxygen Sensor Heating, Checking
Oxygen sensor heater for oxygen sensor, checking
NOTE:
The oxygen sensor heating circuit is monitored by the On Board Diagnostic (OBD). Check DTC memory.
- Connect Vehicle Diagnostic, Testing and Information System VAS5051 or VAG 1551 Scan Tool and select engine electronics control module by entering address word "01", [1][2]Scan Tool Connecting and Initial Checks . When doing this the engine must be at idle.
Indicated on display
Rapid data transfer HELP
Select function XX
- Press buttons -0- and -8- to select function "Read Measuring Value Block" and confirm entry with -Q- button.
Indicated on display
Read Measuring Value Block
Input display group number XXX
- Press buttons -0-, -4- and -1- to select "display group number 041" and confirm entry with -Q- button.
Indicated on display
Read Measuring Value Block 41 ->
1 2 3 4
- Check resistance of oxygen sensor heater.
- Press -C- button.
- Press buttons -0-, -4- and -2- to select "display group number 042" and confirm entry with -Q- button.
If the specification is not attained:
- Check voltage supply for oxygen sensor heater.
- Check oxygen sensor signal wire and activation, Oxygen Sensor Signal Wiring and Actuation, Checking
Checking voltage supply for oxygen sensor heater
Component location of 4-pin harness connector of oxygen sensors.
- Check fuse for oxygen sensor heater.
- Disconnect 4-pin harness connector of particular oxygen sensor.
- Connect multimeter (voltage measurement range) between sockets 1 (B+) and 2 (Ground (GND)) using test leads from VAG1594 connector test kit.
- Operate starter briefly.
Specification: approx. battery voltage
If there is no voltage reading:
- Connect multimeter (voltage measurement range) between socket 1 (B+) and vehicle Ground (GND) using test leads from VAG 1594 connector test kit.
- Operate starter briefly.
Specification: approx. battery voltage
If there is still no voltage reading:
- Check for open circuit and/or short circuit in wiring between fuel pump relay and socket 1 on the relevant oxygen sensor connector (on wiring harness) via fuse.
If the voltage supply is OK:
- Connect multimeter (voltage measurement range) between socket 2 (switched Ground (GND) connection from engine control module) and B+ terminal using test leads from VAG 1594 connector test kit.
- Start engine.
Specification: approx. battery voltage (fluctuating)
NOTE:
At certain points in the operating range the engine control module "switches" (cycles) the Ground (GND) connection to the oxygen sensor heater. That means, it repeatedly connects and disconnects the Ground (GND) connection at these points. For this reason the voltage reading on the tester may fluctuate.
- Switch ignition off.
If there is no voltage reading:
- Connect VAG 1598/31 test box to wiring harness for engine control module. DO NOT connect to engine control module itself, Connecting VAG 1598/31 Test Box
- Check for open circuits in the following wiring connection:
Heated Oxygen Sensor (HO2S) -G39
Connector on wiring VAG 1598/31 test
harness, socket box socket
2 5 (Ground (GND))
Heated Oxygen Sensor (HO2S) 2 -G108
Connector on wiring VAG 1598/31 test
harness, socket box socket
2 4 (Ground (GND))
Oxygen Sensor (O2S) after Three Way Catalytic Converter (TWC) -G130
Connector on wiring VAG 1598/31 test
harness, socket box socket
2 63 (Ground (GND))
Oxygen Sensor (O2S) 2 after Three Way Catalytic Converter (TWC) -G131
Connector on wiring VAG 1598/31 test
harness, socket box socket
2 6 (Ground (GND))
Resistance in wiring: max. 1.5 Ohm
If the wiring is OK but the oxygen sensor heater still has no Ground (GND) connection:
- Replace particular oxygen sensor.
- Display readiness code, Readiness Code Reading. Readiness code must be generated if DTC memory was erased, Readiness Code, Generating