98 Vert will not start until I unhook battery and reattach. Windows and radio do not work until I reattach battery. Horn, headlights, A/C do work before I reset battery. After I reset the battery, car starts fine but 5-10 minutes later after being turned off everything needs to be reset again.
I checked codes after starting up:

C1255 H
B0361 H
B0363 H
B0441 H C
U1064 H

All codes reset and do not reappear until I have another no start routine.

Battery voltage did decrease from 12.65 to 12.33 overnight. Battery is 10 months old.

Any ideas?

Thanks

 

I'll jump this up to the top of the page just in case anyone else can help him out with some other ideas.

Got your email Dan. Like I said, good luck with the repair. I was lucky enough to figure out it was my BCM with the help here on the forum. Looks like you are already at that point. I just do not post a lot on the C5 section since I have been trouble free since the fix.

If anyone else has any tips for him, just let him know.

 

I'm going to take a quick shot but your problem is probably going to require the help from 8Vette7 or Bill Curlee. The C1255 code is the EBCM and its showing an H for history. Might not be anything or it might be a biggie but the fact there's no C on it is a good sign. I have a 98 as well and the EBCM can be on the rear axle or on the drivers side firewall. The older ones are in the rear axle location, newer ones are on the firewall by the engine.

The next 3 codes B0361,363,441 are all related to your HVAC system and only one of them is current. You might have a short there causing that. The last one, the U1064 is loss of communication with the BCM which is being caused by you disconnecting the battery.

Here's what I'd do if I were you. I'd go ahead and disconnect the battery. Reconnect then clear all codes before starting. Start and drive the car for a short distance, then pull over and get your codes again. See what is current. If your car won't restart and you only have the one current code, it might be pulling the battery down to where it won't start. Also test the battery and alternator to make sure you're getting correct voltage when the car is running. Lastly, there are two big trouble spots on C5s and there are a ton of threads on them. Bill Curlee will vouch for this. The ignition switch and the starter solenoid connections. Make sure both of those are in good shape. Hope this gets you off on the right path. Pull those codes and report back please.

 

I had better luck. My vert's BCM would not wake up and I installed the normally closed switch in the place of the BCM power fuse. (I think it was fuse #26?) I Then purchased a used BCM on eBay which has the exact same service/part number. I think this is very important from what I have read. It was from a wrecked '98 coupe vett with 6-speed trany. My car is '98 vert with auto trany.

I installed the used BCM and it came on immediately. The lights, radio, and windows worked.

No problem waking it up. But No engine response. I had to do the 3 step learning process between the BCM & PCM to get the engine to turn over. I did install a 12 volt trickle charger during the learning process to be sure the battery voltage did not drop below 10.5 volts during the learning process.

After the learning process, the engine started and stopped 4 times. I waited 30 seconds and the engine started on the 5th try, and it has run great for over one day now. So far I have found nothing that needs to be programmed by the dealer. Everything works including traction control.