Engine Coolant Temperature (ECT) Sensor, Checking

Engine Coolant Temperature (ECT) Sensor, Checking

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

Test requirements






- The respective fuses of Motronic Engine Control Module (ECM) -J220- 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-.
- Engine must be cold.

Function test

- Connect diagnostic tester.
- Switch ignition on.
- Under address word 33, select "Diagnostic mode 1: Check 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:






1) If a temperature is indicated which differs greatly from ambient temperature of sensor, check sensor wires for contact resistance.

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

Note: The temperature climbs in increments of 1.5°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.

Continuation of test if indication is approx. -46.5°C:

Vehicles > 08.99






- Disconnect 4-pin connector -1- from Engine Coolant Temperature (ECT) Sensor -G62- with Engine Coolant Temperature (ECT) Sensor -G2- (-2-).






- Bridge terminals 1 + 3 of connector using the respective adapter cables and observe the indication on display.

Vehicles 09.99 >






- Disconnect 4-pin connector -1- from Engine Coolant Temperature (ECT) Sensor -G62- with Engine Coolant Temperature (ECT) Sensor -G2- (-2-).






- Bridge terminals 3 + 4 of connector using the respective adapter cables and observe the indication on display.

Continue for all vehicles

If indication jumps to approx. 141.0°C:
- End diagnosis and switch ignition off.
- 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.
- Generate readiness code.

If indication remains at approx. -46.5°C:
- End diagnosis and switch ignition off.
- Check wires according to wiring diagram.

Continuation of test if indication is approx. 141.0°C:

Vehicles > 08.99






- Disconnect 4-pin connector -1- from Engine Coolant Temperature (ECT) Sensor -G62- with Engine Coolant Temperature (ECT) Sensor -G2- (-2-).

Vehicles 09.99 >






- Disconnect 4-pin connector -1- from Engine Coolant Temperature (ECT) Sensor -G62- with Engine Coolant Temperature (ECT) Sensor -G2- (-2-).

Continue for all vehicles

If indication jumps to approx. -46.5°C:
- End diagnosis and switch ignition off.
- 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.
- Generate readiness code.

If indication remains at approx. 141.0°C:
- End diagnosis and switch ignition off.
- Check wires according to wiring diagram.

Checking wiring

- Connect test box to control module wiring harness, connect test box for wiring test.

Vehicles > 08.99






- Check wires between test box and 4-pin connector to Engine Control Module (ECM) for open circuit according to wiring diagram.
Terminal 1 + socket 33
Terminal 3 + socket 14
Wire resistance: max. 1.5 ohms

Vehicles 09.99 >






- Check wires between test box and 4-pin connector to Engine Control Module (ECM) for open circuit according to wiring diagram.
Terminal 3 + socket 53
Terminal 4 + socket 67
Wire resistance: max. 1.5 ohms

Continue for all vehicles

- 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:

Vehicles > 08.99






- Perform a resistance measurement at Engine Coolant Temperature (ECT) Sensor -G62- terminal 1 (Ground (GND)) and 3 (signal).

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- Measure resistance at Engine Coolant Temperature (ECT) Sensor -G62-, terminals C (signal) and D (Ground -GND-).

Continue for all vehicles






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 is in range A and corresponds to a resistance of 1.5 to 2.0 k ohms
80°C is in range B and corresponds to a resistance of 275 to 375 ohms

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.
- Generate readiness code.

If no malfunctions are detected in the wires and the resistance values are OK:
- Replace Motronic Engine Control Module (ECM) -J220-.