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545i “overheating” glitch (a real mystery)

593 Views 5 Replies 4 Participants Last post by  Burning2nd
Hi y’all! I’m about at my wits end with my car currently! I have a 2004 545i with just under 60k on the odometer. I’ve been driving it for a year and put about 15 thousand miles on it and when I first got it I had an issue where an “over heated engine” warning would appear on the idrive then disappear. I went ahead and replaced the water pump (with an OEM), all the temp sensors, and did a coolant flush and that was that. I hadn’t seen the warning for about 6 months until yesterday when it appeared with the chime of death about 300 miles from my house. This is what is odd. The warning appears, the tachometer rolls back, then just as it goes into limp mode for about one second the odometer rolls back to normal and the warning goes away after 10 seconds. There is no hot engine warning, it just goes straight to the “overheated engine” warning. Granted I was going about 90mph up some steep mountain passes. It seemed to happen more so going up a hill than on the flat. However I had a OBD scanner in the car and it was sitting at 210-220 degrees F according to the scanner for most the flat stuff (which it chimes about some as well). Needless to say It kept chirping at me off and on for about 3 hours and I made it home just fine. Heat works fine, when I turn on the AC the fan kicks on immediately, it has plenty of coolant. I am wondering if anyone has had a similar issue, I’m thinking one of my wires may be shorting out or a sensor is going bad. I am hoping it is not the ECU. Anyhow, if anyone has experienced this or has an idea of what it may be let me know! I would appreciate it greatly!
1 - 2 of 6 Posts
scan tool... see what the actual temp is..

see what the status of the thermostat is

do you turn on the heat when this happens? Do you have heat?
I think thats a bad idea, You probably had a harness problem *what you need to do is view live data all the time while driving
confirm your acutal temp, and make sure you have heat when the event happens
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