Engine Coolant Temperature (ECT) sensor, checking
NOTE:
Use only gold-plated terminals when servicing terminals in harness connector.
Recommended special tools and equipment
- V.A.G 1526 multimeter or V.A.G 1715 multimeter
- V.A.G 1594 connector test kit
- Wiring diagram
Requirement
- The respective fuses of Diesel-Direct fuel injection system must be OK:
Refer to Electrical Wiring Diagrams, Troubleshooting & Component Locations
- Battery voltage must be at least 11.5 volts.
- Ground (GND) connections between engine and chassis must be OK.
- Parking brake must be engaged.
- For vehicles with automatic transmission, selector lever must be in -P-.
- Engine must be cold.
Function test
- Connect diagnostic tester. Refer to Diagnostic tester, connecting
- Switch ignition on.
- Under address word 33, select "Diagnostic mode 1: Check measured values."
- Select 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 not obtained:
- End diagnosis and switch ignition off.
- Check wires to Engine Control Module (ECM) according to wiring diagram. Refer to Engine Coolant Temperature (ECT) sensor, checking .
If specified value is obtained:
- Start engine and let run at idle.
- Check specified value of coolant temperature at idle:
| PID | Diagnostic text | Specified value: | ||||
| 05: | Coolant temperature | Temperature value must rise evenly | ||||
NOTE:
- The temperature increases in increments of 1.0 ° 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.
- End diagnosis and switch ignition off.
Check wires to control module
- Connect test box (1598/42) to Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) -J248- wiring harness using adapter cable (V.A.G 1598/39-1). Refer to Test box, connecting for wiring test
- Disconnect 4-pin connector -B- from Engine Coolant Temperature (ECT) Sensor -G62- with Engine Coolant Temperature (ECT) Sensor -G2-.
- Check wires between test box and 4-pin connector for open circuit according to wiring diagram.
Terminal 3 + socket 52
Terminal 4 + socket 53
Wire resistance: max. 1.5 Ω
- Check wires for short circuit to each other, to vehicle Ground (GND) and to B+.
Specified value: ∞ Ω
If no malfunctions are found in wires:
- Measure resistance between terminals C + D on sensor.
See diagram for specified value
Range A displays resistance values for the temperature range of 0 to 50 ° C, range B displays resistance values for the temperature range of 50 to 100 ° C.
Read-out examples:
- 30 ° C corresponds to a resistance of 1500 to 2000 Ω
- 80 ° C corresponds to a resistance of 275 to 375 Ω
If specified value is not obtained:
- Replace Engine Coolant Temperature (ECT) Sensor -G62- with Engine Coolant Temperature (ECT) Sensor -G2-.
WARNING:
- The cooling system is under pressure.
- Danger of scalding when opening!
- Erase DTC memory of Engine Control Module (ECM). Refer to Diagnostic mode 4: Reset/erase diagnostic data
- Generate readiness code. Refer to Readiness code, generating
If no malfunctions are detected in the wires and the resistance values are OK:
- Replace Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) -J248-. Refer to Engine Control Module (ECM), replacing .