Check the ECT and thermostat. Some are rusted out, and never close. test system as in this table.
1. Check the coolant level in the radiator and coolant recovery reservoir. 2. With the key in the "off" position, proceed as follows: a. Remove the engine coolant temperature (ECT) sensor harness connector. b. Attach the Rotunda Service Coolant Temperature Monitor Harness 007-00064 as a jumper between the PCM and the ECT. c. Attach the Rotunda 73 Digital Voltmeter 105-00051 or equivalent to the thermostat monitor harness. Voltage values (0-5vdc) may now be monitored while the sensor retains its connection to the wiring harness. 3. Vehicles equipped with electric engine cooling fan(s) must have a fan running during this test (high or low speed may be used). Two methods may be used to turn the fan(s) on: a. Disconnect the A/C compressor clutch power supply and turn the climate control to A/C "ON", or ... b. Disconnect the power supply to the cooling fan and supply 12 volts direct to the fan connector from the battery. 4. Place transmission in "park" or "neutral". 5. Start the engine and allow to idle throughout this test: a. Allow engine to run for 2 minutes, then record ECT voltage. b. From now on, record ECT voltage every 60 seconds. c. When the ECT voltage trend changes direction or changes only slightly (0.03 volts or less) from the previous reading, record this as the thermostat opening voltage. d. Use the "Voltage and Corresponding Temperature Chart" shown below to obtain actual coolant temperatures. 6. If the opening voltage is GREATER then 0.75 volts (less than 180 °F / 82 ° C), or 0.85 volts (170 °F / 77 ° C) for 2.3L HSC engine only, replace the thermostat. Refer to the dealer Master Parts Catalog for correct thermostat usage. 7. If the thermostat opening voltage is LESS than 0.75 volts (greater than 180 °F / 82 ° C), or 0.85 volts (170 °F / 77 ° C) for 2.3L HSC engine only, the thermostat is good and should NOT be replaced. The "Cooling System Diagnosis Chart" should be referenced for further instructions. NOTE: A Rotunda New Generation Star Tester (NGS) 007-00500 or the Rotunda Service Bay Diagnostic System (SBDS) 001- 00001 may be used to monitor the ECT on vehicles equipped with Data Communications Link (DCL). The SBDS sequence to use for the screen is "Toolbox Electronic Engine Control and DCL - item". NOTE: A ground may be required for some applications. NOTE: Running this test with the vehicle in gear or with the A/C compressor clutch engaged (running) will cause improper diagnosis.
NOTE: The 10 °F opening temperature difference for the 2.3L HSC engine is due to the ECT sensor location.
Sunday, July 5th, 2009 AT 4:53 PM
