Coolant Temperature Sensor/Switch (For Computer): Testing and Inspection
Engine Coolant Temperature (ECT) Sensor -G62-, Checking
Recommended special tools and equipment
- VAG1526 multimeter or VAG1715 multimeter
- VAG1594 connector test kit
- Wiring diagram
Test requirements
- The respective fuses of Engine Control Module (ECM) -J623- must be OK
- Parking brake must be engaged or else daylight driving lights will be switched on.
- Engine must be cold.
Function test
- Connect diagnostic tester.
- Switch ignition on.
- Under address word 33, select "Diagnostic mode 1: Checking measured values."
- Select the measuring value "PID 05: Coolant temperature".
- Check specified value of coolant temperature:
PID Diagnostic text Specified value:
05: Coolant temperature approx. coolant temperature
If specified value is obtained:
- Start engine and let run at idle.
Specified value: Temperature value must rise evenly
NOTE:
- The temperature increases in increments of 1.0 degree C.
- If the engine shows problems in certain temperature ranges and if the temperature does not climb uniformly, the temperature signal is intermittent and the sensor should be replaced.
- Engine Coolant Temperature (ECT) Sensor -G62- is a temperature-dependent resistance. If e.g. moisture in a harness connector leads to a false sensor signal (effect is like resistance connected in parallel), this falsification can still be in a range that is not recognized by the control module.
- If a malfunction regarding Engine Coolant Temperature (ECT) Sensor is stored, control module operates with a calculated replacement value.
If no realistic indication follows:
- Disconnect connector from Engine Coolant Temperature (ECT) Sensor -G62-.
- Use adapter cables from V.A.G 1594 connector test kit to connect V.A.G 1526 portable multimeter to terminals 1 and 2 of sensor for resistance measurement.
Read-out examples:
Range A displays resistance values for the temperature range of 0 to 50 degree C, range B displays resistance values for the temperature range of 50 to 100 degree C.
- 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 engine coolant temperature sensor.
- Read readiness code. If DTC memory was erased, readiness code must be generated again.
If specified value is obtained:
- Connect V.A.G 1598/31 test box to wiring harness of Engine Control Module (ECM) Scan Tool Connecting.
- Disconnect connector from Engine Coolant Temperature (ECT) Sensor.
The following wire connections must be checked for short circuit to B+, Ground (GND) and for open circuit
2-pin connector at V.A.G 1598/31 test box or
wiring harness, terminal Engine Control Module (ECM)
1 (Ground -GND-) 108
2 (signal) 93
- Repair open circuit in wiring or short circuit if necessary.
- In addition, check both wires to each other for short circuit.
Specified value: Infinity Ohms (no continuity)
If no malfunction is found in wires:
- If no malfunction was recognized for the previous tests.
- Replace Engine Control Module (ECM)
- Read readiness code. If DTC memory was erased, readiness code must be generated again