Starts and then dies

This is a new one for me. Car starts fine but then immediately dies after one or two seconds. 90 g-body with vnt electronics and a fwd 3 bar cal. Codes 12 , 66 (yes I checked it twice), 53, 41 and 55. I am not concerned about the 12 or the 55. The 53 as I understand it is ok to have on a redone cal. the 66 is not in the in the 90 FSM so I have no idea as to what that is all about. the 41 is alternator related, but would that shut down the car? I tried a new ASD with no change. I do have an MSD 6al2 box in the car, but to my knowledge that should either work or not, and not cause this issue (but I could be wrong - may need to bypass the box to see what happens). What might be the symptoms with a bad coil?

Thanks in advance for any leads on this.

Has the car ever run on this SBEC before?

Does the car have a factory alarm system?

I ask because the trouble you are having is exactly what happens when an SBEC for a car with factory alarm is used on a car that does not have it. I think it also may act this way if there was a factory alarm and it has not been properly deactivated (by unlocking the driver's door with the key).


Barry

I found a reference to code 66 over on TD. It's no ccd messages. If your car doesn't have the bus, it will set the code if the ECU you have is looking for it. Like you said, 53 is typical of redone cals.

Are you running a VNT turbo? The VNT codes are 64, 65, & 67. So I'm not sure what to tell you...

I have been running this cal for 4 or 5 years with no issues (till now). The car had no alarm (90 Daytona CS AGS - vnt car). No vnt on it anymore and all the vnt selinoids are still intact (just not doing anything). The cal was set up for manual boost control. I am running a super 50 hybrid.

There was another member who's VNT SBEC was throwing crazy codes and not running right. I believe it was determined to be the result of a failing ECU most likely a chip in there somewhere not functioning correctly any longer.

The SBEC was bad. I tired a new ASD with no change, Same with a different HEP and Coil. Even bypassed the MSD with no change. The car is all set up for 3 bar with +40's etc. but I threw in a 2 bar SBEC and the can ran (not well but at least beyond the 1 or 2 seconds. So I removed the 3 bar chip out of the bad SBEC and put into the other SBEC and I appear to be fixed. I just have to re-set the chip in whatever goop they use and I should be back to where I left off before all this. What is normally used to reset the chip? I had read hot glue and silicone but not sure which to use.

Well, I am too late to be helpful i suppose but i have had this issue from failing SMEC/SBEC as well. I have also seen a cal chip go bad and cause a cal that worked perfectly to work badly all of a sudden and changing just the chip fixed the problem. So it could be either the chip or something on the board. Sounds like yours was something on the board.

As far as the 'potting compound', i've never reinstalled anything over any of the chips i've replaced.

I still think the 'bad' SBEC has the security bits set in EEPROM somehow...

I had two SMECs do this after i cranked a 3.0 with the main ground disconnected.. I hurt something in the harness which then hurt the SMEC. It would start and then die after a second. I replaced the SMEC and new one ran ok for maybe a minute and then did the same thing. I ended up replacing the whole harness out of a junkyard for $30 rather than spend the time diagnosing it and replacing the damaged computer AGAIN. So clearly there is something in the computer that has a failure mode of 'works for a second then stops'.

That was many years ago. If the same thing happened today i would probably beat myself up about diagnosing it until i could tell you EXACTLY what happened.

I agree that the bad sbec can likely be reset. I will pm you on a possible fix.

Back from the dead thread. Just an update. In 2016 my socketed 3 bar SBEC with a cal quit working. As noted above it would start and then quit after a second or two. I put the stock 2 bar SBEC back in and the car would start and run. So I figured that the 3 bar sbec was dead and ordered another. The car ran fine after that with the new to me socketed 3 bar so I figured the original 3 bar sbec was dead and I had the proper fix. Fast forward three years and the same thing happened again. Car would start and then quit but start and run with the stock SBEC. So after some knowledgeable folks pointed to the BCM in my 90 g-body, I sourced another BCM from someone with a big pile of parts and knowledge and now the car runs again on the 3 bar SBEC I thought was dead. Still not sure what the real issue is, but it looks like the BCM was the culprit or at least was part of the propblem. The car was behaving like it had the alarm system, but the car did not have one.