Engine Coolant Temperature Sensor: Notes
NOTE:
All voltage and continuity tests should be performed with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless specifically stated differently in testing procedures. For help with diagnostic testing. See WIRING DIAGRAMS .
Location of Engine Coolant Temperature (ECT) sensor and harness connection. See COMPONENT LOCATIONS .
- Allow engine to cool to room temperature approximately 68°F (20°C).
- Disconnect ECT sensor harness connector. Using DVOM switched to resistance range. Connect DVOM to ECT sensor terminals No. 1 and 2, using adapter cables from (VW 1594) connector test kit. See Fig 1.
- Resistance must be approximately 1500-3000 ohms. See ECT SENSOR RESISTANCE table. If resistance is incorrect, replace ECT sensor. If YES: Check wiring between sensor and Engine Control Module (ECM) as follows:
- Connect (VAG 1598) test box to ECM wiring harness using (VAG 1598/5) adaptor cable. See CONNECTING VAG 1598 TEST BOX . ECM is not connected.
- Check continuity between socket 45 of test box and terminal No. 1 of ECT sensor harness connector (Resistance must be 1.0 ohm maximum). See Fig 2.
- Check continuity between socket 30 of test box and terminal No. 2 of ECT sensor harness connector (Resistance must be 1.0 ohm maximum). See Fig 2.
- Check both wires for short circuit to each other.
- Check for a short or open circuit between sensor harness connector and ECM harness connector (terminal No. 30 and/or terminal No. 45). See Figure.
- If problem exist, repair as necessary.
- If circuit are okay, replace ECM. After replacement of ECM, see ECM IDENTIFICATION and ECM CODING under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS article. See WIRING DIAGRAMS .
ECT SENSOR RESISTANCE
| Temperature | Ohms |
|---|---|
| 68°F (20°C) | Approx. 2500 |
| 176°F (80°C) | Approx. 330 |