Temperature Gauge Wont Clear car wont start

[amalyshev]

Hi guys,

Many searchs yielded no results.

2003 E85 z4, 70K miles.

Problem: when the temperature outside is over ~50+ F the car starts fine. When the temp is below and the key is turned to on position the temperature gauge jumps to hot and stays there, when this happens the engine cranks over but wont start.( normally it turns to hot and clears back to cold before start) Sometimes if i let it sit in the on position for 5-10 min and its between 40-50 outside it will clear, after which the cars starts as it should.

any ideas what is causing this?

Thank you! and happy new years!

 

[amalyshev]

Could it be the coolant temperature sending unit?
PS its not throwing any codes

 

[bcworkz]

I think that's plausible. If the engine's cold but the ECU thinks it's at operating temperature, it would probably fail to start. And if it thinks it's over temperature, it may refuse to start as a protective measure. (Guessing on that one) It may be worth simply replacing it on a guess, it's not expensive. However, I think it's hard to get to. Far rear intake side of head down near the head gasket.

 

[amalyshev]

thanks for the info bcworkz

 

[amalyshev]

are there any other sensors or sensitive wiring ( prone to damage) associated with the temp gauge ??

 

[bcworkz]

There's several temp sensors, none would affect the temp gauge in the dash other than the ECT sending unit. If it's a wiring issue, it would likely be right at the sending unit. The other end of the wire is at the ECU, which is well protected.