2008 CTS PCM Fuses blowing

[John May]

I am having a re occurring problem with my 2008 CTS Cadillac 3.6direct injection vehicle breaking down.

I have brought it to several shops , one shop just changed the PCM fuses in the fuse block under the hood, the second shop changed and reprogrammed the PCM , then the last just changed the same fuses they did in January . It seems like when i am going at higher speed 45-50 and traffic stops- i hit the brakes to stop and at that point it kicks the car offline and will not restart (fuses blow) . both shops checked continuity in the wiring and all good. The Trans was changed out last year by GM ,

Searching if anyone else has suggestions or has experienced the same issue .

 

[Bruce Nunnally]

Do you have any DTCs (diagnostic trouble codes)?

So you are driving normally, hit the brakes, and the car goes dead. Upon examination which fuses are blown?

When you apply the brakes NOT at speed are there any issues?

Did the dealer consider it could be an anti-lock brake system ABS fault / short and diagnose?  

 

[Logan]

Hmm.....sporadic, intermittent fuse blowing can be very difficult to find. Your better off if the fuse is blowing all the time. 

Is it the PCM or like Fuse1 or Fuse2 blowing? There are odd and even fuses for the injectors. 

Likely a wire harness is rubbed thru somewhere. Can be a very small spot near a bracket or the sharp corner edge of a cylinder head making intermittent contact. 

.....All it takes is one little wire strand or rub thru to make contact.... 

Being the trans was swapped out a year ago is a interesting clue. Related? Likely.... but who knows. 

You'll have better luck looking at every inch of the engine harness untouched. Look at brackets and the harness routing for any possible areas where the harness may be rubbed thru. Don't wiggle or move the harness at all until you look at every inch for any suspect areas.  

Can also be elsewhere.....parking brake levers....brake pedal arms.....anywhere where sharp edges can rub thru the harness. 

Don't know the details of the trans swap.....could be something in the internal trans harness. Kind of depends exactly which fuse is blowing. Not knowing what the exact fuse is.....your just guessing.  

 

Also....does the car have a sunroof? Sunroof leaks can wet the harness under the carpet and mat. 

Has the car ever been wrecked? Wrecks can cause unnoticed crush damage to the wires inside the harnesses.