Coolant Temperature Sensor/Switch (For Computer): Testing and Inspection
Engine Coolant Temperature (ECT) sensor -G62-, checking
Special tools and equipment
- VAG1526A
- VAG1594A
- VAG1598/31
- VAS5051 with VAG5051/1
or
- VAG1551 with VAG1551/3B
Test requirement:
- Engine cold
Test sequence
- Connect VAS5051 tester or VAG1551 scan tool and select the control module for engine electronics using "address word" 01. Connecting VAS 5051/VAG1551 Scan Tool
Engine must run at idle for this.
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.
Indicated on display:
Read Measuring Value Block Q
Input display group number XXX
- Press buttons -0-, -0- and -4- to select "display group number 004" and press -Q- button to confirm input.
Indicated on display
Read measuring value block 4 ->
1 2 3 4
- Check indication in display field 3.
NOTE: With cold engine, coolant temperature (in display field 3) must approximately match the Intake Air Temperature (in display field 4).
Display Group 004:
If display field 3 does not have a realistic indication:
- Disconnect connector at coolant temperature sensor.
Coolant temperature sensor with square connector:
- Connect multimeter between terminal 1 and 3 of connector for resistance measurement.
Coolant temperature sensor with oval connector:
- Connect multimeter between terminal 3 and 4 of connector for resistance measurement.
All models
Range A shows the resistance values for the temperature range from 0 to 50 degree C, and range B shows the values for the temperature range from 50-100 degree C.
Read-out examples:
- 30 degree C corresponds to a resistance of 1500 to 2000 ohms
- 80 degree C corresponds to a resistance of 275 to 375 ohms
If specified value is not obtained:
- Replace coolant temperature sensor.
If specified value is obtained:
- Connect VAG1598/31 test box at wiring harness to ECM, do not connect ECM. Wiring and Component Testing Using VAG1598/31 Test Box
Coolant temperature sensor with square connector:
- Check the following wire connections for open circuit and short circuit to Ground (GND) and B+:
Harness connector VAG1598/31 test box
Terminal Socket
1 (signal) 108
3 93
Coolant temperature sensor with oval connector:
- Check the following wire connections for open circuit and short circuit to Ground (GND) and B+:
Harness connector VAG1598/31 test box
Terminal Socket
3 93
4 (signal) 108
All models
- Check both wires to each other for short circuit.
- Repair open circuit or short circuit if necessary.
If no malfunctions are found in wires:
- Replace Engine Control Module (ECM).