Coolant Temperature Sensor/Switch (For Computer): Testing and Inspection
Engine Coolant Temperature (ECT) Sensor -G62-, Checking
Recommended special tools and equipment
- V.A.G 1526A multimeter
- V.A.G 1594A connector test kit
- V.A.G 1598/31 test box
Test requirements:
- Fuses for engine electronics OK
- Engine cold
Checking function
- Connect diagnostic tester.
- Switch ignition on.
- In diagnostic function "33 - OBD", select "Mode 1: Checking measured values."
- Select the desired measuring value "PID 05: Coolant temperature".
- Specified value: approx. ambient temperature
NOTE: If a temperature is indicated which differs greatly from ambient temperature of sensor, check sensor and sensor wires for contact resistances and open circuit.
- Start engine and let run at idle.
- Specified value: Temperature value must rise evenly
NOTE: The temperature increases 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.
- End diagnosis and switch ignition off.
If indications do not resemble description:
Checking internal resistance
- Disconnect electrical harness connector -2- from Engine Coolant Temperature (ECT) Sensor -G2-/-G62- at rear coolant pipe.
NOTE:
- The illustration depicts the engine removed from behind.
- Disregard -item 1-.
- Connect multimeter between terminal -C- and -D- of sensor for resistance measurement.
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 corresponds to a resistance of 1500 to 2000 ohm
- 80 degrees C corresponds to a resistance of 275 to 375 Ohms
If specified value is not obtained:
- Replace Engine Coolant Temperature (ECT) Sensor -G62-.
If specified value is obtained:
Checking wire connections
- Connect test box to wiring harness of Engine Control Module (ECM), ECM is not connected. Test Box, Connecting For Wiring and Component Test
- Check the following wire connections for open circuit according to wiring diagram:
Harness connector Terminal Test box Socket
3 108
4 (signal) 93
Specified value: Wire resistance max 1.5 Ohms
- Check wires for short circuit to each other as well as to B+ and Ground (GND).
- Specified value: Infinite Ohms (no continuity)
- If necessary, repair wire connection.
If no malfunctions are found in wires:
- Replace Engine Control Module (ECM).
Final procedures
After repair work, the following work steps must be performed in the mentioned sequence:
1. Check DTC memory see "Mode 3: Check DTC memory". Mode 3: Check DTC Memory
2. If necessary, erase DTC memory see "Mode 4: Reset/erase diagnostic data". Mode 4: Reset/Erase Diagnostic Data
3. Generate readiness code. Readiness Code, Generating
- End diagnosis and switch ignition off.