Trailblazer Control Unit Failure Causing Overheat Issues

Had a similar situation with my 2015 Equinox diesel last year. I've got decent experience with basic repairs, but control module issues aren't my strong suit. The symptoms matched yours exactly, overheating, CEL, and coolant problems. Turned out there was a loose connection at the engine control module causing communication faults between systems. The coolant pressure sensor wasn't communicating properly with the control unit due to a damaged wire harness connector. Workshop found the software glitch was actually stemming from this faulty connection. Total repair was 95 Euro to replace and reseal the connector plus clear the diagnostic codes. Quick question, have you scanned for specific error codes? Also, when exactly does the overheating typically occur (idle, highway speeds, etc.)? This info would help determine if you're dealing with the same car diagnostics issue I had. Sharing your specific codes and overheating patterns would help pinpoint whether it's a similar connector problem or something else in the control system.

Just had my 122917 KM service done last month, and wanted to add that I found the root cause of my issue. The control module was indeed getting faulty readings, but it wasn't just a connectivity issue. The CAN bus system was functioning normally, turns out the coolant temperature sensor itself was the culprit. It was sending incorrect data to the control unit, causing the system to malfunction. Had the sensor replaced and got the control module recalibrated. The software glitch cleared up right after, and the overheating warnings stopped. Temperature now stays steady at both idle and highway speeds. No more coolant leaks either since the system isn't building excessive pressure anymore. Total fix was about 4 hours of labor plus parts. The diagnostic scan showed P0118 and P0217 codes before the repair, which pointed directly to the temp sensor issue.

Thanks for sharing the outcome, really helpful to know the root cause was the temp sensor and not the wiring issue like in my case. These control unit problems can be tricky to diagnose since the symptoms often overlap. When my Equinox had similar issues, I initially thought it was just a faulty connection like I mentioned before. But after reading about your temp sensor fix, it makes me wonder if I should have had my shop do a more thorough check of the sensor array. The car diagnostics only showed the communication errors in my case, but maybe the sensors were starting to drift too. The CAN bus system on these models is pretty robust, but when sensors start sending bad data, it can definitely throw everything off. Your case is a perfect example of how a single faulty sensor can cascade into multiple systems showing errors. Good call getting the control module recalibrated after the sensor replacement. That's something I learned from my repair, even after fixing the physical problem, sometimes the software needs to be reset to clear any stored glitches from when the system was getting bad readings. Quick question, did you notice any change in fuel consumption while the sensor was faulty? My repair actually improved my fuel economy, which I wasn't expecting.

Thanks for asking about the fuel consumption, that's actually something I noticed but forgot to mention! While the sensor was acting up, I was definitely burning more fuel than usual. I'd estimate about 15-20% higher consumption, especially during city driving. After the repair, fuel economy went back to normal within two tanks. Makes sense when you think about it, the engine control module was getting incorrect temperature readings, so it was probably running a richer fuel mixture to compensate for what it thought was high engine temps. The data link between the temp sensor and control module is crucial for optimal fuel management. Your experience with the wiring seems pretty common from what I've learned through this whole process. The car diagnostics can sometimes point to CAN bus communication issues when really it's just garbage data from a bad sensor throwing everything off. Glad I got it sorted before any serious damage occurred. Really appreciate all the input from everyone. Hopefully this helps someone else troubleshoot similar control module issues down the road.