Engine - Coolant Temperature Sensor/Switch: Testing and Inspection

NOTE: Perform the following test only when directed.

ECT Sensor Resistance Inspection
1. Drain the engine coolant. (See COOLING SYSTEM SERVICE WARNINGS.) (See ENGINE COOLANT REPLACEMENT.)
2. Remove the ECT sensor.




3. Place the ECT sensor in water with a thermometer, and heat the water gradually.




4. Measure the resistance between the ECT sensor terminals A and B using an ohmmeter.
- If not as specified, replace the ECT sensor.
- If the ECT sensor is okay, but PID value or PCM terminal 38 voltage are out of specification, carry out the "Circuit Open/Short Inspection".

Circuit Open/Short Inspection
1. Remove the PCM.




2. Connect the SST (104 Pin Breakout Box) to the PCM as shown.
3. Tighten the connector attaching screw.

Tightening torque:
16 - 23 N.m {1.6 - 2.4 kgf.m , 12 - 17 ft.lbf}




4. Inspect for an open or short circuit in the following wiring harnesses by probing the applicable sensor and SST (104 Pin Breakout Box) terminals with ohmmeter leads.
- If there is an open or short circuit, repair or replace wiring harnesses.
- If there is no open or short circuit, replace the ECT sensor.

Open circuit
- ECT signal circuit (ECT sensor connector terminal A and PCM connector terminal 38 through common connector)
- GND circuit (ECT sensor connector terminal B and PCM connector terminal 91)

Short circuit
- ECT signal circuit (ECT sensor connector terminal A and PCM connector terminal 38 to GND)
- GND circuit (ECT sensor connector terminal B and PCM connector terminal 91 to GND)

5. Install the ECT sensor.