Coolant Temperature Sensor/Switch (For Computer): Testing and Inspection

Fig 1 Powertrain Control Module:

To perform a complete test of the engine coolant temperature sensor and its circuitry, refer to DRB scan tool and appropriate Powertrain Diagnostics Procedures. To test the sensor only, refer to the following:

1. Vehicles equipped with air conditioning:
a. Disconnect the negative battery cable at battery.
b. Remove Jeep/Truck Engine Controller (JTEC) mounting bolts and remove JTEC. Do not disconnect three 32-way connectors from JTEC.

Fig. 66 Engine Coolant Temperature Sensor:

2. Disconnect wire harness connector from coolant temperature sensor.
3. Engines with air conditioning:
- When removing the connector from sensor, do not pull directly on wiring harness.
- Fabricate an L-shaped hook tool from a coat hanger (approximately eight inches long).
- Place the hook part of tool under the connector for removal.
- The connector is snapped onto the sensor.
- It is not equipped with a lock type tab.

Sensor Resistance (OHMS) - Coolant Temperature Sensor/Intake Air Temperature Sensor:

4. Test the resistance of the sensor with a high input impedance (digital) volt-ohmmeter.
- The resistance (as measured across the sensor terminals) should be as shown in the chart.
- Replace the sensor if it is not within the range of resistance specified in the chart.
5. Test continuity of the wire harness between the JTEC wire harness connector and the coolant sensor connector terminals.
- Refer to Diagrams/connector Views.
- Repair the wire harness if an open circuit is indicated.
6. After tests are completed, connect electrical connector to sensor.
- The sensor connector is symmetrical (not indexed).
- It can be installed to the sensor in either direction.