Engine Coolant Temperature (ECT) Sensor, Checking
Engine Coolant Temperature (ECT) Sensor, Checking
NOTE: Use only gold-plated terminals when servicing terminals in the 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
Test requirements
- Fuses on E-box in engine compartment, left side, must be OK.
NOTE: Fuses on this fuse holder are labelled "SB" in the wiring diagram.
- Fuses on fuse holder in instrument panel, left side, must be OK.
NOTE: Fuses on this fuse holder are labelled "SC" in the wiring diagram.
- Battery voltage must be at least 11.5 Volts.
- Ground (GND) connections between engine and chassis must be OK.
- All electrical consumers such as, for example, lights and rear window defroster must be switched off.
- For vehicles with automatic transmission, selector lever must be in -P-.
- Engine must be cold.
- Ignition switched off.
Function test
Observe safety precautions.
Observe rules for cleanliness.
- Connect diagnostic tester.
- Switch ignition on.
- Under address word 33, select "Diagnostic mode 1: Check measured values."
- Select the measuring value "PID 5 ($5): Coolant temperature".
- Check specified value of coolant temperature:
- 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.
If specified value is not obtained:
- Disconnect 2-pin connector -1- from Engine Coolant Temperature (ECT) Sensor -G62-.
Checking resistance
- check resistance of Engine Coolant Temperature (ECT) Sensor -G62- between terminals using adapter cables.
Range A displays resistance values for the temperature range of -10 to 45 degrees C, range B displays resistance values for the temperature range of 50 to 105 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 300 to 350 ohms
NOTE: Engine Coolant Temperature (ECT) Sensor -G62- has a negative temperature coefficient (NTC). This means: the higher the temperature the lower the resistance value.
If specified value is not obtained:
- Replace Engine Coolant Temperature (ECT) Sensor -G62-.
CAUTION:
- 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 04 - Erase DTC Memory
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes
If specified value is obtained:
- Check wires to Engine Control Module (ECM) according to wiring diagram.
Checking wires to Engine Control Module (ECM)
- Connect test box to 60-pin connector of wiring harness, connecting test box for wiring test. Test Box, Connecting For Wiring Test
Engine Control Module (ECM) is not connected.
- Check wires between test box and 2-pin connector to Engine Control Module (ECM) for open circuit according to wiring diagram.
Terminal 1 + socket 10
Terminal 2 + socket 14
Wire resistance: max. 3.0 ohms
- Also check wires for short circuit to each other.
Specified value: infinity ohms
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data. 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 value is OK:
- Replace Engine Control Module (ECM) -J623-.