Why does my car think it's coolant is -39 degrees?

[blackbuick87]

My car is VERY hard to start. When it does start I get a code 15, and naturally the car is pig rich since the ScanMaster reads -39 degrees (the same every time)

Once the engine gets the coolant temp up to around 80 degrees the ScanMaster starts reading actual temp and the BLMs go back to normal.

Sensor problem or ECM problem?

 

[Jimn8or]

It sounds to me like the ECM isn't receiving the temp signal from the coolant sensor alright. Start easy, change out the coolant sensor, then throw in your spare ECM if that doesn't help...then start looking at the wiring/grounds, really carefully if the problem is still there.
HTH
Jim

 

[blackbuick87]

Thanks for the reply Jim. Is the TR coolant sensor specific to TR's, or did all Regals use the same sensor?

Just want to know before I talk to the knuckleheads at Autozone

 

[RBE17]

Another way to check (at least on my truck) is to disconnect the IAC sensor and jumper resistors across the connector. Find one that will give you close to normal operating temp. I did this on my truck and drove it like that until I got the sensor and changed it. Changed sensor and all was well.

HTH,


Steve.

 

[machinegun]

I will conlude that you ECM is not seeing proper coolant temp. However before changing the sensor here a a couple of things to check. First remove the plug to the coolant sensor. With a digital volt ohm meter set to volts, check both sides of the plug. I can not remmember which wire but one should be hot. The black one I beleive. You should have plus 5 volts here. If you do then using that five volts, use your meter and jump across the plug. See how many volts. If they are close then your ECM and the yellow wire going back to the ECM should be good, no guarantee but a good start. I would then replace the sensor. Hope this helps.

 

[Jimn8or]

Originally posted by blackbuick87
Is the TR coolant sensor specific to TR's, or did all Regals use the same sensor?

Just want to know before I talk to the knuckleheads at Autozone

Let the knuckleheads at the parts stores sell oil filters...buy the TR specific[?] CTS from GM. I guess I don't need to explain to you how important the right part, sending the right signal is to your ECM and overall running performance of your TR. Machinegun's description above, is a great way to trouble-shoot before you go to GM. gnttype.org has a great malfunction codes referrence that gives the specific voltages you will be looking for.
HTH
Jim