Coolant temperature sensor always fails

MARTINCOBALT

MEMBER
2010 CHEVROLET COBALT
2.2L
4 CYL
2WD
AUTOMATIC
160,000 MILES

After an overheating I change the radiator fan, the thermostat and that resolve the problem, but few days later the coolant temperature sensor fail and the A/C compressor doesn't turn on because the temperature sensor didn't read the motor temperature. So I replace it with a new wiring harness for this sensor. Works fine for a week, but the same problem with this temperature sensor continue.I changed it four times, some times with a replacement from AutoZone and finally the last two times I use the AC Delco original, but I still have the same problem (work fine for a week). Then the CBM fail and I replace it with a re-manufactured CBM programmed to my VIN number of the car. Work perfect for one month, then the coolant temperature sensor failed again and the A/C did not turn on. When this happen I decide to check the sensor ground, the voltage and all looks okay, good ground and 4.8 volt from CBM. So I disconnect the battery for two minute and connected again and then the car star reading the coolant temperature and the A/C work fine. That situation still happen once a week. So I don't know how to fix that problem. My question is, could be the CBM? Because everything else is working fine. Or could be any other problem? By the way the car does not show the check engine light. But I know that that the check engine light work fine because after I change the CBM I get the camshaft code, so I replace it and the light goes off. Please help.
Thanks,
Martin

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,755 POSTS

Hi:

I'm not sure what you mean by CBM. Do you mean PCM or ECM?

When this happens and the light turns on, what happens if you disconnect the sensor and then reconnect it? Also, you checked voltage. Was it when the light was on or off?

Let me know.

Joe

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Tuesday, November 12th, 2019 AT 6:54 PM

MARTINCOBALT

MEMBER
4 POSTS

Hi Joe,
Sorry, yes I refer to the ECM (the computer). Also when the car stop reading the coolant temperature sensor with this new computer (re-manufactured) the dashboard don't gave me any check engine light (don't turn on); just the A/C compressor turn off and no reading of the coolant temperature on dashboard. Before disconnect the battery I disconnect the temp sensor and check the ground and the voltage on the wire harness that is at 4.8 volts, so I reconnected the sensor again and nothing happen (no reading), then I disconnect the battery few second, reconnect and then star reading the coolant temperature and the A/C star working fine. I think the temp sensor cables are okay because when I tested I get the voltage and good ground, Also I test the sensor and work fine (beside that, I change this sensor four times). So I think my next step is to change the hole cables from the computer plug to the temperature sensor to be sure that is not the problem, beside that I don't know what else to do. Could be the new computer? Because I bought a re-manufactured computer. Please let me know what else I can do.
I really appreciate your time and help on my problem.
Thanks,
Martin

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Wednesday, November 13th, 2019 AT 5:40 AM

JACOBANDNICKOLAS

MECHANIC
109,755 POSTS

Hi:

I have to be honest, since this issue didn't begin until after replacing the ECM, that is my first suspect. Rather than replacing the wires between the ECM and the sensor, disconnect each side and check resistance in the wire (continuity). Move the wire around to see if there are changes. But, I suspect there won't be. A wire doesn't care if the battery is disconnected and then reconnected again to start working. However, the ECM may reset.

Let me know what you find.

Joe

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Wednesday, November 13th, 2019 AT 5:53 PM