2005 BMW 325i Repair Question
Engine turns over but won't start
Have you checked to see if there is any water ingress in the control unit box on the Dr. side of the engine compartment? Sometimes, the coolant temp sticking to red indicates a faulty DME. But not always. I think that is what you should focus on. You need to find out the actual input to the DME from the engine coolant temp sensor is. If it is correct then you have a faulty DME. If it is not correct then you have a faulty coolant temp sensor; which has a lot of functional input to the vehicle's actions and will result in various problems similar to what you have.
But beside all that, the basics should be checked to see what is being not being given to start the car. Fuel and Spark mostly, but don't forget EWS. You should have an input from the EWS control unit to the DME to enable start. That is one check that will be made easiest with a scan tool. But, if you don't have one you can monitor the input or output-which ever is easiest for you-and see if there is a change in status.
For a stepped process I would suggest you start with checking for water ingress(check input/output of the coolant temp sensor), then check EWS funtion(maybe try another key if you have one), check fuel psi to the rail, check spark with a spark tester(something you can get from any parts house).
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