"Engine hot turn off AC" displayed on dash

TGEYER

MEMBER
2008 CHEVROLET EQUINOX
3.4L
V6
2WD
AUTOMATIC
150,000 MILES

The vehicle is not running hot, however when this happens both cooling fans come on, temperature gauge drops to 0. Replaced temperature sensor with "standard" brand sensor. Problem went away for about 3 weeks, then reappeared, replaced sensor again thinking it was defective. Vehicle operated okay for a week, then it happened again. Checked 5v ref voltage at sensor, checked for corroded terminals at engine harness to ECM connection. Replaced temperature sensor with Ac Delco sensor and replaced sensor connector pig tail, bled cooling system, no air found in system. Vehicle operated okay for 3 days then problem reappeared. Any ideas?

Saturday, December 11th, 2021 AT 7:23 AM

1 Reply

KASEKENNY

MECHANIC
18,907 POSTS

We need to start with a couple of things. First let's check for codes and make sure you have the P0128 which is pretty common with this issue.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

If you do have this code then based on what you did, the likely cause of this is the thermostat.

I am not sure why when you replace the sensor it is ok for a while other than that is a coincidence so to confirm this we should run through this info and make sure the scan tool is reading the sensor correct.

If the sensor is reading the temperature correctly then it should show on the gauge so if the gauge is not showing the engine getting hot, then we may be missing something on the sensor/wiring side, but this testing should help us find that.

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