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. Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks", 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-, -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.
If display field 3 does not have a realistic indication:
NOTE: Intake air hose between Mass Air Flow (MAF) sensor and intake air elbow must be removed in order to be able to reach the coolant temperature sensor
- 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 0-50 °C, and range B shows the values for the temperature range from 50-100 °C.
Read-out examples:
- 30°C corresponds to a resistance of 1500 to 2000 Ohms
- 80°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. Refer to "Scan Tool Testing/Wire And Component Test Using VAG1598/31 Test Box", Testing and Inspection
Coolant temperature sensor with square connector:
- Check the following wire connections for open circuit and short circuit to Ground (GND) and B+:
Harness connector Terminal VAG1598/31 test box Socket
1(signal) 93
3 108
Coolant temperature sensor with oval connector:
- Check the following wire connections for open circuit and short circuit to Ground (GND) and B+:
Harness connector Terminal VAG1598/31 test box Socket
3 108
4(signal) 93
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).