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Category: Chevy
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Experience:  ASE certified tech ADVANCED LEVEL SPECIALIST. Wisconsin certified emissions state inspector
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2001 chevy malibu temperature gauge not working. engine check

Resolved Question:

2001 chevy malibu temperature gauge not working. engine check light is on. have changed senser still no temperture reading on gauge.
Submitted: 6 years ago.
Category: Chevy
Expert:  AMEDEE replied 6 years ago.



DO you know the code number in the computer?

Customer: replied 6 years ago.
Took the vehicle to auto zone for scan. Scan number came up as PO128. Cooliant temp is always low. Probable causes #1- check coolant level is fine. #2 Thermostat defective - heat from heater core is hot. #3 Engine cooliant temperature sensor defective- bought replacement, installed same problem with temp gauge readings. (tested old ECT with DVM and heat gun OHMS values would change when heated up) 5volts supply to ECT is present. After car is started (cold condition) 10 seconds later dual cooling fans for radiator turn on because of no feedback from ECT sensor. Testing coolant level sensor in coolant reserve bottle at this time time to verify working condition. Thanks for your reply
Expert:  AMEDEE replied 6 years ago.



YES... that is correct!


Codes: P0128

Problem: Faulty thermostat

Test & Fix: The default of a trouble code P0128 is to run the cooing fans and make the temperature gauge inoperative. This code indicates the engine did not warm up as fast as it should have. Check for the thermostat to be stuck open. Replace the thermostat and retest. Monitor the engine temperature. It should reach 195 degrees F within a few minutes.



1. Review the engine temperature through the scan tool to reach a warm engine in a reasonable amount of time.

2. Verify good coolant level and condition.

3. Replace the thermostat.


Potential Causes:

Cooling System

Tips: This code shows that the engine has not reached a predetermined temperature based on engine run time and airflow entering the engine. A stuck thermostat will cause this code. The temperature gauge may be inoperative with this code set.


P0128 Engine Coolant Temperature Below Thermostat Regulating Temperature - With Automatic Transmission


Possible Causes

Check the operation of the thermostat (it may be stuck open)
Coolant level is too low and the coolant mixture is incorrect
ECT sensor connector is damaged (inspect pins for damage and for moisture)
ECT sensor signal circuit has a high resistance condition
ECT sensor has failed

AMEDEE and other Chevy Specialists are ready to help you
Customer: replied 6 years ago.
Do I need to use a scan tool to reset this code PO128. Removing power from the vehicle battery has no turned off engine fault light. Because I get good heat from the heater core after a short drive with vehicle I would like to reset the system to see if it would set the error code again. Connecter at the ECT is dry and corrision free. ECT wires had continuity to the next connecter by the alternator. Coolant level sensor switch unplugged and a jumper put across the plug will cause low level indication on dash board,so that seems to be working as it should.
Expert:  AMEDEE replied 6 years ago.
Which sensor are you testing? Where is it located?

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