Coolant Temperature Sensor/Switch (For Computer): Testing and Inspection
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
- 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 day time driving lights will be switched on.
- Ground (GND) connections between engine and chassis must be OK.
- 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 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 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.
Continuation of test if indication is approx. -40 degrees C:
- Disconnect 4-pin connector from Engine Coolant Temperature (ECT) Sensor -G62- with Engine Coolant Temperature (ECT) Sensor -G2- (arrow).
- Bridge terminals 3 + 4 of connector using the respective adapter cables and observe the indication on display.
If indication jumps to approx. 143 degrees 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. Diagnostic Mode 4: Reset/Erase Diagnostic Data
- 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 to control module according to wiring diagram.
Continuation of test if indication is approx. 143 degrees C:
- Disconnect 4-pin connector from Engine Coolant Temperature (ECT) Sensor -G62- with Engine Coolant Temperature (ECT) Sensor -G2- (arrow).
If indication jumps to approx. -40 degrees 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. Diagnostic Mode 4: Reset/Erase Diagnostic Data
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes
If indication remains at approx. 143 degrees C:
- End diagnosis and switch ignition off.
- Check wires to control module according to wiring diagram.
Check wires to control module
- Connect test box to control module wiring harness. connect test box for wiring test. Test Box, Connecting For Wiring Test
- Check wires between test box and 4-pin connector to Engine Control Module (ECM) for open circuit according to wiring diagram.
Terminal 3 + socket 93
Terminal 4 + socket 108
Wire resistance: max. 1.5 Ohms
- Check wires for short circuit to each other.
Specified value: Infinite Ohms
- 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 found in wire:
Checking resistance
- Measure resistance at Engine Coolant Temperature (ECT) Sensor -G62-, terminals C (signal) and D (Ground GND).
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 is in range A and corresponds to a resistance of 1.5 to 2.0 kohms
- 80 degrees 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. 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 Motronic Engine Control Module (ECM) -J220-.