I've got a 04 LLY. I've been having a issue with the temp gauge. When up to temp the gauge would bottom out like the engine was cold. At that time the truck would start running rough and go into like a high idle. This would go back and forth. When the gauge was reading correctly it would run ok. So I replaced the temp sensor. Now the gauge won't read at all but the truck runs ok. Any ideas on what this could be? Thanks
Weird coolant temp issue
- Thread starter Summitlly
- Start date
Are the rest of the gauges functioning ok to your knowledge? You have an edge monitor or efilive to monitor coolant temp? Or even a tech 2?
Sent from my XT1585 using Tapatalk
Sent from my XT1585 using Tapatalk
The temp gauge works off of the same temp sensor as the ECM(the 2 wire sensor next to the t-stats). When it goes open circuit, it goes full cold and the ECM thinks the engine is -40 degrees, and the gauge goes all the way down, when it reads it will go back up. If you put a jumper wire across the 2 terminals in the CTS plug, it should go full hot, ding hot engine, and all kinds of other things as well as run pretty poorly(but you can do it for a quick wiring check to verify the wiring to the CTS is good). I will ONLY use GM coolant temp sensors because of all the bad out of the box aftermarkets I've gotten. But check the wiring real close where it goes by the FICM as that is a known wear point.
Well I found the issue. After digging through the harness and finding nothing. Put all back together. I started it and all was fine. So I figured it was probably a broken wire that I missed. While it was running I started wiggling things around and it went out again. It was the plug end that goes on the sensor. Not sure why I didn't start there. I like to make things rough on myself. Thanks again guys.