TowGMC
Full Access Member
Had a very strange overheating problem when towing the race car trailer a week ago.
First let me say that I've hauled the same trailer and race car all over the country and the water temp has never strayed from the 210 mark on the gauge. For the past several years I've also had a second trans cooler that has kept trans temps below 195 in all heat and traffic conditions. So nothing has changed for the towing and towed setups.
This past weekend after driving 30 or 40 minutes, on long upgrades in 4th or 5th gear the water temp would climb up to what appears to be about 225 on the gauge. Trans temps never went above 190. Ambient air temp was in the mid 80's. And in the morning part of the trip the temps were in the 70's and I wasn't running A/C. Later I was running A/C and it did exactly the same thing. As soon as I'd crest the hill (running 65-70) and down the other side the temp dropped right back down.
What's also odd is that the ambient air temp on the car would then read +10 degrees from actual temp (verified by the others I was towing with), and at one point the display said that both front TPMS air pressure sensors failed. And when I stopped for fuel, the battery was dead and I needed my jump box to get started.
But since I've been back everything is working properly- TPMS, ambient temp, battery etc. This happened towing east 400 miles on Thursday, and 400 miles back Sunday.
Called my dealer tech from the track (yes I have a great tech that works on my Denali) and he suggested disconnecting the battery for 10 minutes to reboot the Body Control Module. And to replace the coolant temp sensor. Did both and made no difference. He's now stumped too. I'm going to drop it off with him as soon as I get a chance but there are no fault codes stored or otherwise any indications that anything went wrong.
So does anyone have any ideas, or experienced the same thing?
(I put this in general because I don't know if the problem is engine, electronics, interior (BCM) or what)
First let me say that I've hauled the same trailer and race car all over the country and the water temp has never strayed from the 210 mark on the gauge. For the past several years I've also had a second trans cooler that has kept trans temps below 195 in all heat and traffic conditions. So nothing has changed for the towing and towed setups.
This past weekend after driving 30 or 40 minutes, on long upgrades in 4th or 5th gear the water temp would climb up to what appears to be about 225 on the gauge. Trans temps never went above 190. Ambient air temp was in the mid 80's. And in the morning part of the trip the temps were in the 70's and I wasn't running A/C. Later I was running A/C and it did exactly the same thing. As soon as I'd crest the hill (running 65-70) and down the other side the temp dropped right back down.
What's also odd is that the ambient air temp on the car would then read +10 degrees from actual temp (verified by the others I was towing with), and at one point the display said that both front TPMS air pressure sensors failed. And when I stopped for fuel, the battery was dead and I needed my jump box to get started.
But since I've been back everything is working properly- TPMS, ambient temp, battery etc. This happened towing east 400 miles on Thursday, and 400 miles back Sunday.
Called my dealer tech from the track (yes I have a great tech that works on my Denali) and he suggested disconnecting the battery for 10 minutes to reboot the Body Control Module. And to replace the coolant temp sensor. Did both and made no difference. He's now stumped too. I'm going to drop it off with him as soon as I get a chance but there are no fault codes stored or otherwise any indications that anything went wrong.
So does anyone have any ideas, or experienced the same thing?
(I put this in general because I don't know if the problem is engine, electronics, interior (BCM) or what)
