RAM 1500 Truck 2WD V6-3.9L VIN X (1999)
Coolant Temperature Sensor/Switch (For Computer): Testing and Inspection
To perform a complete test of the Engine Coolant Temperature (ECT) sensor and its circuitry, refer to DRB scan tool and appropriate Powertrain
Diagnostics Procedures. To test the sensor only, refer to the following:
Engine Coolant Temperature Sensor
1. Disconnect wire harness connector from ECT sensor.
2. 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 Chart
3. 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 SENSOR RESISTANCE (OHMS)-COOLANT TEMPERATURE SENSOR/INTAKE AIR TEMPERATURE SENSOR
chart. Replace the sensor if it is not within the range of resistance specified in chart.
4. Test continuity of the wire harness between the PCM wire harness connector and ECT sensor connector terminals. Repair the wire harness if an
open circuit is indicated.
5. 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.
