Heater Check
Oxygen Sensor Heating For Oxygen Sensors Before And Behind Catalytic Converter, Checking
Special Tools and Equipment
- VAG1526A
- VAG1594A
- VAG1598/31
- VAG1788/10 RPM adjuster
- VAS5051 with VAG5051/1
- or
- VAG1551 with VAG1551/3B
NOTE: The heating circuit of the oxygen sensor is monitored by On Board Diagnostic (OBD),
Check DTC memory.
- Connect VAS5051 tester or VAG1551 scan tool and select the control module for engine electronics using "address word" 01. Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks/Connecting VAS5051/VAG1551 Scan Tool" Testing and Inspection
Engine must run at idle for this.
When indicated on display:
Rapid data transfer HELP
Select function XX
- Press buttons -0- and -8- to select "Read Measuring Value Block" and press -Q- button to confirm input.
When indicated on display:
Read Measuring Value Block Q
Input display group number XXX
- Press buttons -0-, -4- and -1- to select "display group number 041" and press -Q- button to confirm input.
When indicated on display:
Read Measuring Value Block 41 ->
1 2 3 4
- Check specified values in display fields 1 and 3.
NOTE: Increasing engine speed accelerates the obtaining of specified values.
Display group 041:
- Press -C- button.
When indicated on display:
Read Measuring Value Block Q
Input display group number XXX
- Press buttons -0-, -4- and -2- to select "display group number 042" and press -Q- button to confirm input.
When indicated on display:
Read Measuring Value Block 42 ->
1 2 3 4
- Check specified values in display fields 1 and 3.
Display group 042:
If specified value is not obtained:
- Check voltage supply of oxygen sensor heating.
- Check oxygen sensor signal wire and activation.
Checking voltage supply for oxygen sensor heating
Test requirement:
- Fuse for oxygen sensor heating OK
- Fuel Pump (FP) OK, checking. Testing and Inspection
- Disconnect 4-pin harness connector leading to respective oxygen sensor.
- Connect multimeter between terminal 1 and 2 for voltage measurement.
- Start engine.
- Specification: approx. possibly fluctuating battery voltage,
NOTE:
- At certain operating points, the ECM "pulses" the Ground (GND) for oxygen sensor heating. This means that the Ground (GND) is constantly switched on and off at these points. It is therefore possible that the voltage displayed on the tester will fluctuate.
- It is possible to observe the ECM switching oxygen sensor heating on and off within the function "read measuring value block", display group numbers 041 and 042.
If there is no voltage:
- Connect multimeter for voltage measurement as follows:
- Operate starter briefly.
- Specification: approx. battery voltage
If there is no voltage again:
- Check wire connection from terminal 1 to Fuel Pump (FP) relay via fuse for open circuit.
If voltage supply is OK:
- Connect multimeter for voltage measurement as follows:
- Start engine.
- Specification: approx. battery voltage, possibly fluctuating
- Switch ignition off.
If there is no voltage:
- Connect VAG1598/31 test box at wiring harness to ECM, do not connect ECM. Refer to Scan Tool Testing/Scan Tool Connecting and Initial Checks/Connecting VAG 1598/31 Test Box Testing and Inspection
- Check the following wire connection for open circuit:
- Oxygen Sensor (O2S) heater -Z19- bank 1 before catalytic converter:
- Oxygen Sensor (O2S) heater -Z28- bank 2 before catalytic converter:
- Oxygen Sensor (O2S) heater -Z29- bank 1 behind catalytic converter:
- Oxygen Sensor (O2S) heater -Z30- bank 2 behind catalytic converter:
If no malfunctions are found in wires:
- Replace appropriate Oxygen Sensor (O2S).
- Read readiness code. Refer to "Monitors, Trips and/or Drive Cycle (Readiness Code)/Reading, Readiness Code" Testing and Inspection
If DTC memory was erased, readiness code must be re-generated. Refer to "Monitors, Trips and/or Drive Cycle (Readiness Code)/Generating, Readiness Code" Testing and Inspection