Hey all,
I was cruising the archives about a quickly flickering SES light, and there seems to be two causes, one being some kind of connection problem, the other being "limp home" mode. Can anybody tell me some details about the "limp home" mode?
The reason I ask:
I've been having this intermittent problem with my SES light flickering fast and consistent like a strobe light on my completely stock 120k mi 86 GN(everything stock except the nice new radiator from Nick Micale and DirectScan). Is this "limp home" mode? It runs like total crap when the light flashes like this (unresponsive and rich as far as my nose can tell).
Also, although my DS and Compaq laptop sporadically act up, I am able to get a Code 51 (EPROM failure) on both DS and using the SES light while jumping the ALDL port. The previous O2 sensor code has disappeared, but all other settings seem OK on DS. Tonight when I get home I'm going to verify all connections as discussed in the archives, as well as pull the stock EPROM and investigate to see if these are the cause of the problems. I saw a post from Fast Freddie where it could even be the orange ECM "fuse" connection isn't making good contact.
Thanks for any info,
Fred
Yep, that's limp home mode. Things to check:
- EPROM loose in the socket ... reseat
- EPROM
- DirectScan cable too loose/too far on the edge connector causing it to crash the ECM
- Loose connection at ECM to wiring harness
I'm just going to ask to help understand this. If it is an intermittent problem, would the EPROM being loose be the obvious problem? IE hit a bump, SES starts the light show and car runs like crap because the EPROM may have been fine until the bump? I guess I'm just asking that if the problem is intermittent, then the answer is something is loose, not the EPROM itself?
It seems from past problems put out to the list with DS, the problems have always been(as far as I can remember) the cable was too far onto it's connection on the computer, I'd check that. Everybody always mentions making a spacer to keep the connector from going down too far.
The "bump theory" sounds reasonable. The chip sockets get loose over time due to all of us not being able to leave them alone (and plugging and unplugging chips dozens of times!)
The DS problems can crash the ECM if there's a bad connection, interference on the cable that goes to the edge connector, etc, etc, etc. It's plugged onto what amounts to the processor bus, so noise and bad connections can raise all sorts of nasty side effects. It's critical that this connection is solid.
Thanks for the responses, guys. I really appreciate it.
I forgot to mention, I had known about the DS cable position causing problems, so I actually disconnected it from the ECM, and I still had the 'flickering' problem. I think this was also after removing power to the ECM to clear it.
Also, I've never pulled the EPROM - knowledge, time, and money constraints as a grad student have me keeping the car stock... for now
So it could just be corrosion, because I doubt the socket is loose, unless the previous 2 owners messed with it (which could be likely). Unfortunately, I didn't have time to pull the ECM last evening, but the problem did not occur on the way home. So it really is an intermittent gremlin. I'll be sure to let you know as soon as I find out.
I forgot to post my un-eventful discoveries into my intermittent 'limp-home mode' problem. This weekend I pulled the ECM, and all the connections were straight, shiny, and fit tightly. There was a tiny hole on one wire, so I taped over it, but I doubt it was causing the problem. Also, I pulled the EPROM, and that looked good as well, so I cleaned the pins a bit and replaced it.
The only thing I figure is that the door on the ECM case over the EPROM wasn't all that tight, and maybe the EPROM moved (although its carrier was still in very tight). I put everything back together and the problem hasn't come back. (Although the SES lit up steadily today for a bit, I have to check on that *new* problem now...)