Coolant Temperature Sensor/Switch (For Computer): Testing and Inspection
Engine Coolant Temperature (ECT) Sensor -G62-, Checking
Special tools and equipment
- VAG1551 scan tool or VAG1552 mobile scan tool with VAG1551/3B cable
- VAG1598/31 test box
- VAG1526 hand multimeter or VAG1715 multimeter
- VAG1594 adapter set
- Wiring diagram
Test conditions
- Engine must be cold.
Test sequence
- Connect VAG1551 scan tool (VAG1552). Switch ignition on and select engine control module with the "Address word" 01 (Connecting scan tool and selecting engine control module). Refer to "VAG1551 Scan Tool Tools and Equipment
Indicated on display:
Rapid data transfer HELP
Select function XX
- Press keys 0 and 8 for the function "Read measured value block" and confirm entry with Q key.
Indicated on display:
Read measured value block HELP
Input display group number XX
- Press keys 0, 0 and 4 for "Display group number 4" and confirm entry with Q key.
Indicated on display: (1 to 4 = Display zones)
Read measured value block 4 ->
1 2 3 4
- Read off coolant temperature value in display zone 3.
Specification: approx. coolant temperature
If the specification is not obtained:
- Perform check according to following table:
If the specification is obtained:
- Start engine and run at idling speed.
The temperature value must increase uniformly
NOTE:
- Temperature increases in steps of 1.0 °C.
- If irregular engine running occurs in certain temperature ranges and the temperature figure does not increase without interruption, the temperature signal is temporarily interrupted and the sender must be replaced.
- Press -> key.
- Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.
Continuation of check when display approx. -48 °C:
- Pull the 4 pin connector off Engine Coolant Temperature (ECT) sensor (G62) with coolant temperature gauge sender (G2) - arrow-.
- Bridge connector contacts 3+4 using adapter cables from VAG1594 and observe display.
If display jumps to approx. 143 °C:
- Press -> key.
- Press keys 0 and 6 for "End data transfer" function and confirm input with Q key.
- Switch ignition off.
- Replace Engine Coolant Temperature (ECT) sensor (G62).
- Check DTC Memory, if necessary, repair any malfunctions and then Erase DTC Memory,Checking and Erasing DTC Memory. Refer to "Displaying and Reading Trouble Codes/With Manufacture Scan Tool/Check DTC Memory (Function 02)" Testing and Inspection
- Read readiness code. If DTC memory has been erased or engine control module was disconnected from permanent positive, readiness code must be generated again: Refer to "Monitors, Trips and/or Drive Cycle/ Reading Readiness Code" Testing and Inspection
Engine code AWW, Refer to "Monitors, Trips and/or Drive Cycle/Generating Readiness Code" Testing and Inspection
Engine code AWP, Refer to "Monitors, Trips and/or Drive Cycle/Generating Readiness Code" Testing and Inspection
If display remains at approx. -48 °C:
- Press -> key.
- Press keys 0 and 6 for the "End data transfer" function and confirm input with the Q key.
- Switch ignition off.
- Check wiring using wiring diagram.
Continuation of check when display approx. 143 °C:
- Pull the 4 pin connector off Engine Coolant Temperature (ECT) sensor (G62) with coolant temperature gauge sender (G2) - arrow-.
If display jumps to approx. -48 °C:
- Press -> key.
- Press keys 0 and 6 for the "End data transfer" function and confirm input with the Q key.
- Switch ignition off.
- Replace Engine Coolant Temperature (ECT) sensor (G62).
- Check DTC Memory, if necessary, repair any malfunctions and then Erase DTC Memory,Checking and Erasing DTC Memory. Refer to "Displaying and Reading Trouble Codes/With Manufacture Scan Tool/Check DTC Memory (Function 02)" Testing and Inspection
- Read readiness code. If DTC memory has been erased or engine control module was disconnected from permanent positive, readiness code must be generated again: Refer to "Monitors, Trips and/or Drive Cycle/ Reading Readiness Code" Testing and Inspection
Engine code AWW, Refer to "Monitors, Trips and/or Drive Cycle/Generating Readiness Code" Testing and Inspection
Engine code AWP, Refer to "Monitors, Trips and/or Drive Cycle/Generating Readiness Code" Testing and Inspection
If display remains at approx. 143 °C:
- Press -> key.
- Press keys 0 and 6 for the "End data transfer" function and confirm input with Q key.
- Switch ignition off.
- Check wiring using wiring diagram.
Checking wiring
- Connect VAG1598/31 test box to control module wiring harness. The engine control module remains disconnected.
- Pull 4 pin connector off Engine Coolant Temperature (ECT) sensor (G62) with coolant temperature gauge sender (G2) -arrow-.
- Check wiring between test box and 4-pin connector for open circuit using wiring diagram.
Contact 3+socket 93
Contact 4+socket 108
Wire resistance: Max. 1.5 Ohm
- Check wiring between test box and 4-pin connector contact 3 for short circuit to wire contact 4 and to vehicle Ground (GND) using wiring diagram.
Contact 3+socket 108
Contact 3+vehicle Ground (GND)
Specification: Infinity Ohm
- Additionally check both wires for short to battery positive.
If no fault in wire is detected:
- Perform resistance measurement on Engine Coolant Temperature (ECT) sensor (G62) contact C (signal) and D (Ground (GND)).
Scale A shows resistance values for temperature range 0 to 50 °C and scale B the values for temperature range 50 to 100 °C.
Examples:
- 30 °C is in range A and corresponds to a resistance of 1.5 to 2.0 kOhm
- 80 °C is in range B and corresponds to a resistance of 275 to 375 kOhm
If the specification is not obtained:
- Replace Engine Coolant Temperature (ECT) sensor (G62).
- Check DTC Memory, if necessary, repair any malfunctions and then Erase DTC Memory,Checking and Erasing DTC Memory. Refer to "Displaying and Reading Trouble Codes/With Manufacture Scan Tool/Check DTC Memory (Function 02)" Testing and Inspection
- Read readiness code. If DTC memory has been erased or engine control module was disconnected from permanent positive, readiness code must be generated again: Refer to "Monitors, Trips and/or Drive Cycle/ Reading Readiness Code" Testing and Inspection
Engine code AWW, Refer to "Monitors, Trips and/or Drive Cycle/Generating Readiness Code" Testing and Inspection
Engine code AWP, Refer to "Monitors, Trips and/or Drive Cycle/Generating Readiness Code" Testing and Inspection
If there is no fault in the wiring and the resistance measurement values are OK.:
- Replace engine control module.