Checking ECT Sensor Signal
NOTE:
The Engine Coolant Temperature (ECT) sensor is a temperature dependent resistor. If, for example, humidity penetrates a connector (effect same as parallel switched resistor) the sensor signal will be false.
If a Diagnostic Trouble Code (DTC) is stored pertaining to the ECT, the test value block will indicate a replacement value from the intake air temperature over a specific time from the Engine Control Module (ECM). After the time has elapsed, a replacement value for the warm running engine will be included.
- Initiate check of DTC memory and erase. See RETRIEVING DIAGNOSTIC TROUBLE CODES in SELF-DIAGNOSTICS article.
- Select "READ, MEASURING VALUE BLOCK" function 08 using Scan Tool (VAG 1551) input display group number. See "READING/MEASURING VALUE BLOCK (FUNCTION 08)" under OUTPUT DIAGNOSTIC TEST MODES (DTM) in SELF-DIAGNOSTICS article.
- Check display in channel 2. "ENGINE COOLANT TEMPERATURE" displayed in degrees Celsius (°C).
- If an engine coolant temperature value is indicated that seems incorrect in comparison to the ambient temperature or to the beginning of engine warm-up, even though no code has been stored: Check the wiring for short circuit (shunt, e.g. through humidity in connectors). If Okay: Replace ECT sensor. If still NOT Okay: Replace ECM. After replacement of ECM, see ECM IDENTIFICATION and ECM CODING under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS article.