With Generic Scan Tool

Engine Coolant Temperature (ECT) Sensor, Checking

Recommended special tools and equipment
- VAG1526 multimeter or VAG1715 multimeter
- VAG1594 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.
- Engine must be cold.

Function test
- Connect diagnostic tester. Diagnostic Tester, Connecting
- 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: Cooling fluid temperature approx. coolant temperature

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

Indicated1) Cause
approx. -40 degree C Open circuit or short circuit to B+
approx. 143 degree C Short circuit to Ground (GND)

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 should climb uniformly

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.

Continuation of test if indication is approx. -40 degree C:
- Disconnect connector at coolant temperature sensor.

Coolant temperature sensor with square connector:







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

Coolant temperature sensor with oval connector:







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

Continuation for all vehicles
If indication jumps to approx. 143 degree C:
- End diagnosis and switch ignition off.
- Replace Engine Coolant Temperature (ECT) Sensor -G62- with Engine Coolant Temperature (ECT) Sensor -G2-.
- 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. Readiness Code, Generating

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

Continuation of test if indication is approx. 143 degree C:
- Disconnect 4-pin connector -1- from Engine Coolant Temperature (ECT) Sensor -G62- (-2-).

If indication jumps to approx. -40 degree C:
- End diagnosis and switch ignition off.
- Replace Engine Coolant Temperature (ECT) Sensor -G62- with Engine Coolant Temperature (ECT) Sensor -G2-.
- 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. Readiness Code, Generating

If indication remains at approx. 143 degree 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. Test Box, Connecting For Wiring Test

Coolant temperature sensor with square connector:







- Check wires between test box and 4-pin connector for open circuit according to wiring diagram.
Terminal 1 + socket 108
Terminal 3 + socket 93
Wire resistance: max: 1.5 Ohm

Coolant temperature sensor with oval connector:







- Check wires between test box and 4-pin connector for open circuit according to wiring diagram.
Terminal 3 + socket 108
Terminal 4 + socket 93
Wire resistance: max: 1.5 Ohm

Continuation for all vehicles
- Also check wires for short circuit to each other, to vehicle Ground (GND) and to B+.
Specified value: Infinite Ohm

If no malfunctions are found in wires:

Coolant temperature sensor with square connector:







- Connect multimeter between terminal 1 and 3 of sensor for resistance measurement.

Coolant temperature sensor with oval connector:







- Connect multimeter between terminal 3 and 4 of sensor for resistance measurement.

Continuation for all vehicles
Range A displays resistance values for the temperature range of 0...50 degree C, range B displays resistance values for the temperature range of 50...100 degree C.







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

If specified value is not obtained:
- Replace Engine Coolant Temperature (ECT) Sensor -G62- with Engine Coolant Temperature (ECT) Sensor -G2-.
- 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. Readiness Code, Generating

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