View Full Version : 1990 Eldorado displays wrong diagnostic parameters in CCDIC

12-13-12, 05:55 PM
I have a 1990 Cadillac Eldorado, 4.5L PFI, Base model with mismatched ECM data and descriptions... I would like to know if that information comes from the ECM, EPROM, BCM, or the CCDIC itself? I know the ECM talks to the CCDIC via the BCM, but I don't know which one knows the information for diagnostics (ED00 to ED99 data parameters, descriptions, and values).

Most notable is the fact that the my car displays data as if it was TBI vehicle (EDxx readings for only one injector pulse width, one O2 sensor, one fuel trim, etc), however I should be seeing values for a PFI vehicle (Right and Left bank injector pulse width, Right and Left O2 sensors, Right and Left fuel trim, Right and Left O2 cross-counts, etc.)

I'm trying to troubleshoot via the console Information Center (Off + Warm buttons) which allows me to view the ECM data, inputs, outputs, and overrides. I have the red 1990 Eldorado/Seville Factory Service Manual with detailed information about troubleshooting steps however the data fields on the display of my car do not match those in the book. I have confirmed ECM, EPROM, and BCM model numbers and so far they all seem to match the specs but something is still wrong. Any information, especially about where the data originates would be helpful.

I have confirmed the following part numbers with Cadillac and I have verified they are correct in my car.
ECM: 88999176 (216-90 AC Delco) (16132240 Standard Auto).
ECM EPROM: 16147002 (7003ATTS) (PROM ID 1020?)
BCM: 88999224 (1228786 Standard Auto)
BCM EPROM: 16151314 (2342ANXX)

Interesting note, I'm guessing that the ECM EPROM should have an ED99 PROM ID of "7003", however ED99 PROM ID shows "1020" (physical EPROM shows DELCO/ATTS/7003)

Any help at all to point me in the right direction would be greatly appreciated!!

12-15-12, 07:47 PM
Halfway through your post, I was going to tell you your prom was wrong... However, the prom in my '90 is 1020 also and mine displays left and right banks like it should. Your part numbers appear to be correct also via Rockauto.com. This is very weird. Obviously if you have 8 injectors, TBI programs arent going to run it well, if at all.

There are codes that should set if you have mismatched electronics. The diags info and E-codes physically come from the ECM. Whether or not they go through the BCM first before displaying on the DIC, I dont know... It appears that the DIC simply reads from both units just like a computer accessing 2 separate hard drives. As far as I know it stores no information, only serving as a user interface.

Another thing to note is that an incorrect BCM prom has a 1 in 15 chance of matching your key chip and letting you start the car. I can also confirm through my own experience that the ECM, IPC, and CCDIC are compatible across both TBI and MPFI years so I doubt that the part lookups are wrong.

One problem that I have found in owning a 1990 is that because the engine is sort of a 'hybrid' being the only MPFI 4.5L in the lineup, many part lookups from different vendors list it like a TBI. (I had an Advance employee insist that my car did not have a cam sensor while I had the damn thing in my hand! So I just made him look up a '91...) Probably not an issue in your case, but is something to lookout for.

Since we know that the electronics are the same you can surmise that only the PROMS carry any specifics for your year, model, and engine. Maybe it has something to do with how the ECM is reading the PROM? Or the PROM was flashed incorrectly at some point? Just out of curiosity, you can go into the BCM and check the VIN displayed against the actual VIN.

Whats the history on the car, and how does it run? Unless you are some kind of super troll, this has got to be the weirdest problem I've seen on this forum.

12-16-12, 04:05 PM
Unless you are some kind of super troll, this has got to be the weirdest problem I've seen on this forum.

Sevillian273, thanks for the response....Not exactly the most promising though!

Little history: I picked the car up on Craigslist for $1000 "needing a tuneup", it had a misfire and was running rich but otherwise is in excellent shape (new tires, battery, shocks, brakes, very clean interior and exterior, etc). The previous owner picked it up from someone who had it sitting in his yard for years, they were trying to fix it up but gave up on it. I had them take it to their mechanic first for a "tuneup" of new plugs and wires, as well as a state inspection (exempt emissions test). I finally had it in my possession for the first time and it ran even worse... I had it towed to my mechanic after driving it for 6 miles! He found a blown injector bank fuse which made it run 80% better but still had a misfire. (If i hadn't been stranded on the side of the road I would have found this). My guy confirmed the distributor and internals are still in good condition but didn't check the spark plugs themselves. His plate was full so he didn't go beyond that.

I took it home, checked the injectors and 6 of 8 were below spec, 2 of those were nearly shorted, so I replaced all 8. Still had a misfire and is now running extremely rich (I could probably light a match and have a flamethrower out the tailpipe). I did a vacuum test and it's pulling good vacuum (pulling 19-20 psi with a 1-2 psi flutter b/c of misfire), did a fuel pressure/regulator test and it's good. I picked up the red Factory Service Manual for 1990 Eldorado/Seville on eBay and was about to perform an injector Override via the CCDIC to determine which cylinder was misfiring, that's when I noticed the problem that I'm posting about. Everything about the diagnostics says TBI!

I did many online searches, RockAuto, AutoPartsWarehouse, ACDelco.com, gmpartseast.com, and I emailed a Cadillac dealer who helped me track down the correct part and EPROM numbers. I even emailed TunerCat who specializes in programming EPROMs to see if they had any input...everyone is just as baffled as I am. I purchased a reman ECU from RockAuto but I still have the same issue. I think I found an identical 1990 red Eldorado in a junk yard nearby and I'm going to check it out next Saturday. I'm aware of the "uniqueness" of the 1990 4.5L MPFI being one-off year, which is making this hunt interesting.

I agree that the CCDIC is just an interface, and short of tapping into the serial data line with a PC and serial sniffer I think I'm just going to replace the BCM and/or both EPROMs just to make sure. I have a feeling that something is not labeled correctly or was reprogrammed as you mention.

I really wanted this as just a fun car to have around, not the project car it's proving to become. I'm now diagnosing the computer first in order to diagnose the misfire second!

12-22-12, 02:25 PM
Well I found a 1990 Eldorado in a junkyard today and took both the ECM and BCM (with chips). All of the part numbers (and PROM IDs) match what I already had. I still have the same problem of displaying TBI data and overrides rather than PFI. I first replaced the ECM MEMCAL only, then both ECM and MEMCAL from the junkyard car. Same as before. I then replaced the BCM (with EPROM). Same as before. I'm at a total loss. What is telling the DIC that it's a TBI car!? Should I replace the CCDIC next? Are there dipswitch settings somewhere? I now have the ECM and BCM from the junker and I'm still where I was before.

12-22-12, 04:54 PM
Another symptom is the lack of SIR diagnostics from the CCDIC. According to the FSM I should enter diagnostics and have 4 options: "ECM?", "BCM?", "IPC?", and "SIR?", then cycle back. Instead, I'm getting "ECM?", "BCM?", "IPC?", and "DUE TO". From my basic knowledge, airbags didn't exist on TBI cars did they? So more evidence (or symptom, or cause) that my car has identity issues! What the heck is going on here!?

12-23-12, 04:41 PM
You're right, airbags werent introduced until 1990.

This is crazy. I guess if I was in your shoes, my next leap of faith would be to replace the DIC even though I have no evidence for it being responsible or not. It's just the only thing left in the system. I know for a fact that it isnt the IPC since I have an 1989 unit in my car right now. Obviously it's only an info/display issue since everything functions as an MPFI system. Does the TBI info displayed look realistic when the car is running? Does the pulse with for the phantom TBI injectors widen accordingly as throttle increases? And the oxygen sensor?

01-13-13, 03:53 PM
It was the CCDIC. I grabbed nearly every computer from the junkyard car a few weeks ago but finally had a chance to replace the CCDIC today. The one originally in the car was manufactured in 7/88 and the new one was 4/90. As soon as I entered diagnostics and saw "NO SIR CODES" I knew it was better. Finally have all the right ECM DATA values I should have and finally know that the Left bank is running very rich. Now I can diagnose the original problem that got me down this track!!

01-27-14, 02:38 AM
I realize this thread is old and I did not mean to post here, my apologies. I am interestingly enough having this same problem with my '90 Deville giving me the wrong interface when I go into the diagnostics and was pointed here. I meant to reply to the person who pointed me here, so sorry.