Engine Coolant Temperature (ECT) Sensor, Checking

Engine Coolant Temperature (ECT) Sensor, Checking

NOTE: Use only gold-plated terminals when servicing terminals in harness connector of sensor.

Recommended special tools and equipment
- VAG1526 multimeter or VAG1715 multimeter
- VAG1594 connector test kit
- Wiring diagram

Test requirements







- Fuses in E-box (in plenum chamber, left) must be OK:
- Ground (GND) connections between engine and chassis must be OK.
- Parking brake must be engaged or else daylight driving lights will be switched on.
- For vehicles with automatic transmission, selector lever must be in - P - position.
- 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:







If specified value is not obtained:
- Continue test according to the following table:







If specified value is obtained:
- Start engine and let run at idle. The temperature must climb uniformly

NOTE:
- The temperature climbs in increments of 1.0 degrees 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.

- Switch ignition off.

Continuation of test if indication is approx. -40 degrees C:







- Disconnect 2-pin connector from Engine Coolant Temperature (ECT) Sensor - G62 - (arrow).







- Bridge terminals 1 + 2 of connector using the respective adapter cables and observe the indication on display.

If indication jumps to approx. 140 degrees C:
- End diagnosis and switch ignition off.
- Replace Engine Coolant Temperature (ECT) Sensor - G62 -.

WARNING:
- The cooling system is under pressure.
- Danger of scalding when opening.

- Erase DTC memory of Engine Control Module (ECM). Diagnostic Mode 04 - Erase DTC Memory
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

If indication remains at approx. -40 degrees C:
- End diagnosis and switch ignition off.
- Check wires according to wiring diagram.

Continuation of test if indication is approx. 140 degrees C:







- Disconnect 2-pin connector from Engine Coolant Temperature (ECT) Sensor - G62 - (arrow).

If indication jumps to approx. -40 degrees C:
- End diagnosis and switch ignition off.
- Replace Engine Coolant Temperature (ECT) Sensor - G62 -.

WARNING:
- The cooling system is under pressure.
- Danger of scalding when opening.

- Erase DTC memory of Engine Control Module (ECM). Diagnostic Mode 04 - Erase DTC Memory
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

If indication remains at approx. 140 degrees C:
- End diagnosis and switch ignition off.
- Check wires according to wiring diagram.

Checking wiring
- Connect test box to control module wiring harness. Connecting Test Box For Wiring Test







- Check wires between test box and 2-pin connector for open circuit according to wiring diagram.
Terminal 1+socket 93
Terminal 2+socket 108

Wire resistance: max. 1.5 ohms.

- Also check wires for short circuit to each other, to vehicle Ground (GND) and to B+.

Specified value: infinity ohms.

- Erase DTC memory of Engine Control Module (ECM). Diagnostic Mode 04 - Erase DTC Memory
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

If no malfunctions are found in wires:
- Replace Engine Coolant Temperature (ECT) Sensor - G62 -.

WARNING:
- The cooling system is under pressure.
- Danger of scalding when opening.

- Erase DTC memory of Engine Control Module (ECM). Diagnostic Mode 04 - Erase DTC Memory
- 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 Motronic Engine Control Module (ECM) - J220 -.