Engine Coolant Temperature (ECT) Sensor, Checking

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:
- 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. 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:







If specified value is not obtained:
- End diagnosis and switch ignition off.
- Check wires to Engine Control Module (ECM) according to wiring diagram.

If specified value is obtained:
- Start engine and let run at idle.
- Check specified value of coolant temperature at idle:







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.

- 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), connecting test box for wiring test. 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 Ohms

- Check wires for short circuit to each other, to vehicle Ground (GND) and to B+.
Specified value: Infinite Ohms

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 degrees C, range B displays resistance values for the temperature range of 50 to 100 degrees C.

Read-out examples:
- 30 degrees C corresponds to a resistance of 1500 to 2000 Ohms
- 80 degrees C corresponds to a resistance of 275 to 375

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), Diagnostic mode 4: Reset/erase diagnostic data. Diagnostic Mode 4: Reset/Erase Diagnostic Data
- generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

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-.