ecm/ign fuse blowing - GN and T-Type Performance Enthusiasts (GNTTYPE) Forums

deadlois · #1 07-29-2005, 07:51 PM

Basically my battery died and after I replaced the old battery with a new one, my car wont start. I checked the fuses, and the ecm-ign was blown so I replaced it, and it ran for about 30 seconds and then it blew. I replaced the fuse again and I couldn't get the car to start. It turns over strong, but no start but the fuse hasnt blown yet. the ccc fuse was blown too and I replaced it but that had no effect. FYI, when the battery had died I tried a while to jump it, but the battery was just too old and basically had to be replaced, could jumpstarting my car have an adverse effect if done too long? Thanks for any help. BTW I bought my 87 grand national a few weeks ago and I am kind of new to these cars.

milehighGN · #2 07-29-2005, 09:04 PM

How did it run when it was blown? I'm getting a code 42 error and i think that could be it

deadlois · #3 07-30-2005, 12:06 AM

It stopped running when the fuse blew, I should have went a little further on what happened. I just recently replaced the ECM(fried the old one) and I suspected the chip may have been damaged when I fried it, but it started up fine after a jump(had it parked for a couple weeks). I let it run foir about 20-30 minutes, drove to the store, and when I came back battery was dead. When my buddy came over to give me a jump, it started one time and shut off after a high rev. I think that is when the fuse blew. After putting in a new battery couldn't get it to start, then I doublechecked it and found the ecm-ign fuse blown, along with the ccc one, I replaced it and it started on the first try. It ran for about 30 or so seconds real rough and then shut off. Couldn't get it to start again. Now I believe it is possibly the chip, would the vehicle not even start if the chip is bad? The only reason I think that is the problem is because I fried the old ECM with the chip in it, and maybe it just started when tried cause it was almost dead. Thanks for any help.

kenmosher · #4 07-30-2005, 09:38 AM

The vehicle will start even without an EPROM ... it'll set a SES light (usually a code in the 50s) and run off the CALPAK.

If the car wasn't throwing codes, there's a pretty good chance the EPROM is OK. They either work or they don't ... there's no degradation or partial failure.

deadlois · #5 07-30-2005, 05:19 PM

I found out that I can not get an error code reading off the ECM because the fuse keeps blowing(ECM-IGN). Is there anything that would be damaged from excessive jumpstarting that would effect this fuse? I will check the diagram on the site but it is hard to read even when magnified. Thanks for any help.

Keller · #6 07-30-2005, 06:02 PM

Your ECM and/or ignition module may be extra crispy...

I've toasted and ECM in the past by putting my T on a battery charger. It didn't fail immediately and started giving codes occasionaly. Chip was fine.

deadlois · #7 07-30-2005, 07:08 PM

correct me if I am wrong, I disconnected the ECM and put a new fuse in the ECM-IGN slot, and when I turned the key to the on position the fuse still blows. Then is this a possible ignition coil short? Thanks for the feedback.

deadlois · #8 07-31-2005, 07:08 AM

Just found some wiring diagrams that I can read a bit better, and was asking for some advice. I see that the fuse that is blowing(ECM-IGN) goes to ECM pin A6, ESC module, MAF sensor and it looks like it goes to the CCCI pin N. I was wondering to troubleshoot this if I were to disconnect the CCCI and turn the key to the start position with a good fuse in the ECM-IGN slot if that would be a good idea? I want to do this to try and isolate it to the CCCI if that is the actual problem, but I dont want to damage anything. Is this safe? I am pretty sure it is, but I dont want to do anything that maybe damaging. BTW I already had disconnected the ECM and it still blew a fuse, so unless there is a wiring short it rules that on out, right? Thanks again guys.

kenmosher · #9 07-31-2005, 10:06 AM

Disconnecting at the ignition module shouldn't hurt anything and would be a good trouble shooting step. My guess is that you'll find it is the module.

deadlois · #10 07-31-2005, 05:18 PM

Right you are, Ken. I didn't even have to look at anything else, once I got the connector off. The side of the connector where the wire from the ignition goes to was melted on the inside, so looks like I will have to replace the CCCI module and get a new connector at the very least. Do you think I will have to replace the coil on top too? Thanks, you have been a big help.