My brother in law just purchased a 2004 crossfire. He brought it to my house and it wouldn't crank. The lights come on and after a bit the cooling fan revs up ( is this normal?) He pulled the rcb and we resoldered connections ( they still looked good but did it anyway) The ecm will not communicate with any of my scan tools ( also have Alex Peppers scan tool) Where can we start trouble shooting? I do not believe the ecm is working but I don't know an indication to look for. Any suggestions would be appreciated as I would love to take this car for a spin. Thanks

 

Would not crank means different things to different people.
To some it means the engine turns over but does not continue turning over without the use of the starter motor.
To others it means that it will not turn over because the starter motor does not operate.
I think you mean the later because you mention the RCM, but please confirm.

 

Found out that fooling with the key fob and unlocking the doors will sometimes enable the car to start. However, it will stop running and will again be dead( not turn over ) It also still does not communicate with scan tool.

 

It makes it hard if you don't answer the questions asked - we are not there with you and cannot see first hand what is going on.

In any event, if the starter wont engage, I'd turn the key to "ON", wiggle the RCM out, and measure the voltage on pins E 5 and E 6 of the RCM. These are the engine control relay output pins. Pin 6 goes to the PTCM (which you are referring to as the "CPU"). If that pin does not have clean, reliable, 12 volt power, the PTCM will not be fully powered up.

So, my first move would be to verify that. If the pin is dead, you've got to fix THAT first.

If the Starter engages but the car won't start or wont keep running - I'd consider the Crank Sensor or the relay on the RCM that powers the fuel pump. (Of course, you can usually HEAR the pump run when you turn the key to "ON" if you LISTEN.)

 

Thanks Pizza Guy for your reply. Actually, I did answer but due to my inexperience it wasn't readable. I meant that starter would not engage. Since then I found by reprogramming the key, I could get the car to start. I thought it was fixed but then alas, it wouldn't start again. Sometimes the starter will engage momentarily and then quit, the little screen beneath the odometer will say start error. Do I have a bad key fob or security computer? Apologies for not using the proper terminology for these components but I am rapidly learning their names. Thanks guys and Merry Christmas!

 

You can't reprogram the key - the RFID chip in the key is coded to the SKREEM and you cannot alter it. You CAN program the key to lock and unlock the doors, but that's it.

If the starter won't engage, I'd be looking, again, at the "Engine COntrol Relay" output of the RCM. That is, once I assured myself that the battery is healthy and the battery posts and terminals are clean and tight.

I must say, never in six years have I heard of "START ERROR" being displayed. THAT is a new one.

If the SKREEM is bad, the car will crank three times, then you get nothing. Disconnecting the battery and reconnectiong it will get you three more cranks then nothing. You are describing either a flaky engine control relay output from the RCM or a weak/marginal battery or really bad battery posts/terminal corrosion. Be sure and check the battery ground cable where it attaches to the chassi - mine was so bad I changed the battery ground cable ($11 at AutoZone). If the battery voltage falls below (I think it is 9.6 volts) during cranking, the pulse module will drop out and the starter will stop turning.

 

Again, this is the hard part of electronic troubleshooting - you got off on a wild goose chase here. You THOUGHT you reprogrammed the key - what you did was fuss with it and coincidentally, the car started.

Your issue is not the key programming, it's that you have an intermittent start issue and intermittent issues are VERY hard to nail down - even for experienced electronics technicians - often they are IMPOSSIBLE for a "mechanic" to nail down, as mechanics never intended to learn electronic diagnostics or theory.




WHen you get a minute, if you are on Facebook - search and join "Crossfires in the South" on Facebook - the local Atlanta/North Georgia people tend to hang out there. We are getting together in ALpharetta on the 30th at Bonefish Grill.

 

this happen to me at a stop sign 2 weeks ago,everything on the car was working,but would not start,the odd thing was the cooling fan would come on,looked at the rcm,looked brand new,it would start up 24 hrs later, run about a min.,then nothing,tried it again 24 hrs later,started up and ran for a minute,so i put a new rcm in,no more problems,it also got rid of the slight miss i had at idle

 

I'm going over Tuesday with all my spares to have a look.
Most likely the RCM, but we'll see.
I'll report back what I find on this thread.

 

And if YOU are on Facebook, Join "Crossfires in the South" and join the fun as well!

 

I have to come clean and give better info. Yesterday I discovered that the LCD has a bad segment and so what looked like Start error was actually SERrt error, whatever that means.
A kind gentleman is coming over and he has some spare parts and knowledge. Very grateful for the help guys.