ECM fuse keeps burning ??

[Stormn712]

Darn. I had the most reliable XB9S for 7 years now. Not a single problem (except drive belts). Now all of a sudden the ECM pops after a 15 min ride ? What gives ?

 

[rchuff]

Take a good look at the ecm and see if is cracked anywhere . If that looks good than maybe fuse is going bad?

 

[Stormn712]

rchuff,

thanks so very much. I have the Race ecm. which has never failed in it's 10 years. Pulled it out to have a look, however everything looks like new. The ECM fuse has burnt twice now. once before changing the fuel pump and now just recently again? I'm stumped. It's running now, but wont travel far nor without spare 7.5 amp fuses.

 

[Stormn712]

Does any of my Bueller friends have any other thoughts of where to look ? [confused][confused]

 

[nicholas900]

Well in the wiring diagram for an 04 xb, the ecm fuse goes directly to the ecm. Its a yellow wire out of the fuse box, and a yellow wire on the grey connector at the ecm. Its labeled "keep alive memory".

Could be the wire shorting out somewhere between or a bad ecm I guess. Check for rubbed through wires, look in the grey ecm connector for damage.

 

[Stormn712]

Thanks nicholas900,
I removed ECM (Race), fuse block and looked at wires to and from and haven't found any chafed or rubbed wires anywhere. I'm thoroughly stumped. I have the actual "Official Factory Manual" for the '03 XB9S. But can't find anything covering burnt ECM fuse.
I hope you and our other Buellers have some thoughts for me.

 

[Cosworth]

Not having any charging issues or notice the head lamps getting bright then dim are you? Just a though but maybe a VR on the way out.

 

[Stormn712]

Thank you Cosworth,
No such voltage issues visually noticed. Though I did notice that when I removed the neg. batt. lead before removing the ECM and other; the Pos. lead was slightly lose. Can that result in burnt out ECM fuses ?

 

[Cosworth]

I wouldnt think that would cause it but the 7.5amp fuse is pretty small and somewhat susceptible to voltage spikes such as zero to full battery that could be cause by a loose terminal going out and in to contact.

Have you cleaned the battery cables and terminals and tested it?

 

[nicholas900]

When the fuse blows what are the symptoms? What exactley looses power?

 

[Stormn712]

everything seems to work except fuel pump and spark after fuse blows.

 

[nicholas900]

Odd... I can try to help more. But first a few questions.

Is this repeatable? Can you ride it so far and it will pop the fuse every time?

Do you have a test meter or test light?

Are you sure it's supposed to be a 7.5 amp? My 04 is marked on the cover 10 amp.


First test. Pull out the ecm fuse. Turn key on. Hook your test light clamp to battery ground. Check for power on grey wire (middle) at ignition coil or grey wire at the diagnostic link. Either one whatever is easier to get at.

What you got?

 

[Stormn712]

Thank you nicholas900 and all Buellers whom shared their knowledge. It is most appreciated.
I've gone through all your ideas and have only come to this temporary quasi inconclusion.[confused]
Both battery posts were slightly loose. After all the wiring, B.U.S., fuse box, ECM examination and re-installations of all. I snuggly tightened the battery leads and have had no fuse issues in the past month with approx 100 miles traveled. I can only hope that like Cosworth said..the possible spike/surges in amperages with loose leads may have caused the small 7.5 ECM fuse to trip the 5 times before diagnostics. Thanks to all again for your time and generousity of your knowledge. Crossing my fingers.

 

[ztied]

Thats what I was gonna say isnt it a 10 amp fuse?Hope you got it