Intermittent crank no start issue?

BERNADETT4

MEMBER
2008 CADILLAC STS
3.6L
6 CYL
2WD
AUTOMATIC
200,000 MILES

It all started when I kept running out of gas and I had to start getting jumps on my car. So, one day I parked my car, turned it off and after that I could not get it to start; it would crank over but it would not start. So, I changed out the crankshaft sensor and once again it would crank over but it just wouldn't start. So, now 4 months later, I changed out the ECM which was yesterday and now it's quiet it won't say anything the lights will come on and you know but it won't say anything. I need help.

1 Reply

AL514

MECHANIC
4,632 POSTS

Hello, so you had an intermittent starting issue with the old ECM, and now the new one won't even cranks the engine over. If that's incorrect let me know. Where did you get the new ECM and who did the programming for it? And if you were to put the old ECM back in do you still get the intermittent starting issues, or does it not crank it over either?
One last question, does the Check Engine light come on when you turn the key to just to on/run position?

Okay, just looking at the data network in this vehicle, the Instrument Panel Module (IPM) which is behind the glove box is in charge of sending out an ECM/TCM Serial Data Wake Up signal as well as a High Speed GMLAN Serial Data Wake Up signal to all the modules on every network in the vehicle. So, if the IPM does not send out that signal, none of the modules in the vehicle will power up. Usually with GM vehicles the Body Control Module does this, but your vehicle has an IPM instead of a BCM. So, it's taking the place of that module. But this could be the issue if the Check Engine light does not come on when you turn the key to on, and the Instrument Cluster lights up.
Module failures like this can be very difficult to diagnose.
But the IPM acts as a Gateway module where all the networks will communicate through it.
But let us know about the check engine light that comes on first.