My 1993 SDV normally runs like a peach but all kinds of odd things have been happening ever since my wife accidently dropped a dime into an empty cigarette lighter slot (we usually just use it for running a cell phone charger). She picked me up from work with a non-functioning radio and all the other stuff thats run off of interior fuse 11 (I think that's what it was) and so I figured we could wait until we got home to deal with it. During the 25 mile drive, the engine was very subtly running rough and the SES light came on with a E39 TCC fault code. We'd had TCC problems in the distant past (only obvious signs were the SES lights coming on about once a month) but I replaced the TCC in late 2002 and never had a problem since.

I get home, yank the dime out, and replace the burnt out fuse and all is fine with the radio, et al, but when I start it up, now it is idling like crap. Dies on occassion at idle and I figure something must have goosed the system, causing the equivalent of a power surge / temporary power loss, and clearing out the PCM memory. So I run the standard "re-learn" mode of letting it idle 15 minutes, sit in drive with the climate control off for 5 minutes, and then sit in drive with the climate control on for 5 minutes. It idles better but when I take it out for a run, I get an E39 back up within minutes and at some point in the drive, I can feel noticable hesitations occassionaly. When I clear the codes, they pop right back up within five miles. No other codes are observed. Gas milage takes a noticable downturn.

So I take it to Aamco because I figure that it it's the TCC popping in and out which might explain the rough cruising at times (I can't, however, figure what effect the TCC would have on my car sitting motionless in my driveway). Well, the Cadillac Gods were having fun that day because not only are there no codes to be seen, the guys drive it around endlessly and pronounce it a sweet ride. That's wonderful, I guess, but the praise does me no good because with 15 minutes of leaving the shop, E39 is back in the house.

OK, maybe the damn PCM needs to be "rebooted" I figure and I disconnect the battery for the night. I reconnect the next morning, relearn the PCM with the 15/5/5 minute thing, and go driving around. Sure enough, the engine still idles rough on occassion and I get an E39 code.

So what's the deal? Could the shorted circuit from the dime incident possibly have done more damage than just blowing a fuse? (and it was running perfectly prior to the short) I can always bring it back to Aamco but I am wondering if this fault is really something being triggered by an internal failure in PCM and not something in the transmission. I hate the thought of taking it to a dealership because I suspect that they'll replace everything in sight without really diagnosing the problem. And regular mechanics with less of a greedy corporate mind set might not have the tools\training to get at this sort of non-obvious problem.

Any ideas welcome. Also, I live in West Los Angeles so if you have any suggestions of a nearby mechanic with the sorts of skills to deal with this, I'd appreciate learning their names.


Happy New Year!


Nick

Have you checked ALL the fuses and circuit breakers...???

Possibly the power feed to the VCC apply circuit was popped somehow in the process...

My first reaction is that there is no connection between the cigarette lighter circuit and any VCC or driveability issue....can't make a connection. We often use the cigar lighter port for instumentation power and I have seen lots of them overloaded and the fuses popped in development cars. Nothing in my recollection ever happened other than the obvious interior items going dead and recovery with a new fuse has always been fine.

If you are running into stalling and such it may be that the throttle body is very dirty and the idle speed control was at the maximum idle learn offsets which were lost when the PCM was reset. Ideally the idle learn process should have corrected for that but....??? I would recommend a simple throttle body and EGR tube cleaning. This is a quick DIY item. Just hold the throttle blades wide open and look down the bores. Clean the ID of the throttle bores and the backside of the throttle blades with carb cleaner and an old tooth brush. See the two tubes sticking up at you from the floor of the intake manifold...??...those are the EGR tubes and they are not supposed to be full of carbon and crud. Rod them out all the way thru to the manifold passage below with a piece of stiff wire. Disconnect the battery neg terminal again for 60 secnds and drive. Forget the idle learn. The values will reset to the "clean throttle body" default.


Lots in the archives on both of these subjects if you search using "EGR tubes" "VCC" "TCC" etc.

You can check operation of the VCC by lightly touching the brake pedal while driving normally with your left foot with the VCC applied. The brake interlock switch deactivates the VCC when the brake is depressed so you can feel the slight bump when it disables when you touch the brake while maintaining normal load on the drivetrain with your right foor on the accelerator.

Excellent advice. I did check fuse 5 on the right side block of interior relays and fuses (I think that one has something to do with the VCC) but I'll go over them all one by one. What else do I have to do with my time?

Interestingly, the rough idle issue seems to have gone away (it idles just fine) but there is a noticable though subtle roughness (I don't have any other way to describe it) at times when cruising between 40 and 50. The SES light hasn't come on yet but I'll bet that I'll see an E39 when I get home tonightand run the diagnostic. If so, I'm going to go down to Aamco and demand that they take a ride with me at normal operating temps and highway speeds.

Most importantly, thanks for the analysis that exonerates my wife from any blame ("My first reaction is that there is no connection between the cigarette lighter circuit and any VCC or driveability issue....can't make a connection."). This has made her day as it shifts blame from her fumbling fingers to my failure to maintain our car correctly. As a husband of 22 1/2 years, I know that utimately it's better that way.


Thanks again,

Nick