Okay recently I went to start my 1981 eldorado Biarritz and smoke started coming from under the glove box. I took apart the under dash cover and found the ECM was the issue. I removed it and purchased a replacement. Installed the PROM chips to the new unit and the new unit started to sizzle as well so I quickly shut the key. The issue happens when the car is in the “run†position. Can someone guide me through this issue? I cannot start the car without the ECM. The car has 70k miles and was running perfect with no issues before hand.
Hopefully the prom has not been damaged. If it is that may be difficult to replace these days. For 2 ECM's to have smoked you must have a really badly failed device or damaged wiring. Something that isn't protected is being overloaded or some external fault is sending voltage somewhere its not supposed to be.
I have the tool to start troubleshooting that issue. I will have to go out and find it and see what the model number is. I do remember its from OTC. Basically this tool is a box with some switches and readouts on it that plugs into a model specific ECM substitute board. You look at the model number of the ECM then find the corresponding note card and circuit board. You plug the board in in place of the ECU then follow the tests outlined on the note card. The card says which tests to run and what is a pass/fail for each test. It does basic tests of all the wiring and sensors. Its not the end all be all test for anything but I bet would narrow down where to look for your issue.
Without that or a similar tool you will either have to get the service manual and starting testing each circuit with a volt ohm meter or carefully inspect all the devices and harnesses till you find the problem one. It would be nice if you had a clue where to start looking. Maybe opening up the ECU's and looking for the damage you could get lucky and follow the traces to a connector and pins so you know which system to be looking at.
Was any work done recently ?
Hello, first post to this Forum. I have a 1981 triple red Biarittz with the V864 engine that will run in this mode if I turn it on from a small switch installed under the dash. I have been collecting information on the V864 system gradually for future reference on mine if ever the time comes. Came across this thread from another Cadillac Forum so I hope that it is OK to post here. It has some links to several Serviceman Bulletins about the ECM, PROMS and a troubleshooting ladder diagram for diagnosing repeated ECM failures. Hope it helps. Dave
https://www.cadillacforums.com/threads/cadillac-v864-proms-sharing.1017849/#post-17093257 (https://www.cadillacforums.com/threads/cadillac-v864-proms-sharing.1017849/#post-17093257)
Your dash switch most likely disconnects the 3d gear sensor from the transmission which is the 'right' way to disable the system. The system was only allowed to go into 6 or 4 mode when the transmission was in 3rd gear so if it never thinks its in 3rd it just stays in V8 mode. Most of the other methods would cause other issues because the computer didn't understand what was going on.
I don't think we have heard from the original poster for a while. His issue has to be external to the ECU since it happened to 2 different units. Newer stuff is better protected from external issues but this early in the game they were still learning.
I have also read of 8/6/4 cars smoking multiple ECMs, but not a
resolution of the problem. Yes it must be external to the ECM.
I suggest noting the area smoking on the original ECM. To cause
this damage I would expect some kind of power input/output
circuit. That could be the power supply. But more likely its drive
to outside components such as valve activators or solenoids,
which may have shorted out and now draw too much current.
Do not just keep burning up more ECMs, determine the fault. If
a power driver is the only failure, the ECM might be repairable.
The early proms were 2732A parts, which were very cheap for
many micro processors of that era, and we easily made duplicates
of them back then. good luck, Bruce Roe
Hello All,
I’m finally getting back to resolving this issue (car has been sitting since I originally posted this, I would like to send my original ECM to someone to test out which circuit fried does anyone know of someone that can test ECMs?
-Anthony
;D Yeah! Bruce Roe!
Coming in late here, but sounds like a quad driver in the ecu. These controlled high load solenoids, so a shorted component could fry the driver. As far as I know the ecu is not repairable.
Quote from: Dave Shepherd on February 18, 2020, 09:33:57 AM
Coming in late here, but sounds like a quad driver in the ecu. These controlled high load solenoids, so a shorted component could fry the driver. As far as I know the ecu is not repairable.
does anyone know the part numbers for the solenoids? and where they are located?
Quote from: Tonyv_73 on February 18, 2020, 09:13:43 AM
who is that?
See reply #5 in this thread. Send him a PM if he doesn't respond here again.
Quote from: 35-709 on February 18, 2020, 09:50:32 PM
See reply #5 in this thread. Send him a PM if he doesn't respond here again.
Thanks, Hopefully this forum can help resolve the issue before spring!
UPDATE:
Replaced the Air Diverter Valve Solenoids (there was a short in one of them) Plugged in replacement computer and the car starts up, however I am getting nothing on the display for the Fuel Economy readout, the check engine light is on, and I cannot check codes in climate control display. Does anyone know if the ECMs are different between years? (yes I used original PROMS) Im wondering if I have a HT-4100 ECM instead of a V-8-6-4 ECM. If that is the case does anyone have the correct ECM for sale?
Original ECM "KD" 1225120? anyone know which other part numbers will fit?
I'm have a problem to start my '80(368 engine),I need to checkfollowing the service manual if the Ecm is gone,Is really difficult to find and replace the prom un the Ecm?
Thank you.
If you get a remanufactured ECM for it, they used to include a small tool to remove and install the E-prom with. I don't know if it's still included, or even if the ECM is still available anymore. The last time I had to replace one was many years ago.
My question is, is the remanufactured ECM the correct one for 1981? or is it a "one size fits all" for 1979-1985. Ive heard that the ECM needs to be an 81 ECM because of the "Fuel Econonmy" display
Any listing that says 79-85 is for sure wrong. 79 was a completely different animal. No idea what else was the same. Its possible that 80 and 81 were the same but its also possible that 82 could be the same. The prom would tell it what sensors and outputs are needed and which are not.
So what ECM would you recommend if the original part number is “KD†“1225120â€
Tony, I also have an 81 Biarritz with the V864 in it. From the Cadillac Parts & Accessories Manual, Catalog 61A it looks like your ECM is likely the correct one and a reasonably late version as the attachment is the third and last page of the ECM documentation that is shown in it. If can help with anything else please let me know and I will see what I can find out as I have all the manuals that I think were available for this car. Dave
Dave,
It looks like the PN Anthony listed is a Service ECM then according to your chart. It's hard to believe they had so many different original versions. I did notice though there are a lot fewer service PNs. It looks like there are only 4 unique service PNs:
1224760
1224770
1224810
1225120 <<The number Anthony asked about
I pointed them out and captured it....
It sounds like if I had one of these cars I would be placing an inline fuse between each of the solenoids and the ECM. Scary stuff...
Scott
Quote from: Tonyv_73 on March 26, 2020, 10:37:01 AM
UPDATE:
Replaced the Air Diverter Valve Solenoids (there was a short in one of them) Plugged in replacement computer and the car starts up, however I am getting nothing on the display for the Fuel Economy readout, the check engine light is on, and I cannot check codes in climate control display. Does anyone know if the ECMs are different between years? (yes I used original PROMS) Im wondering if I have a HT-4100 ECM instead of a V-8-6-4 ECM. If that is the case does anyone have the correct ECM for sale?
From a small insert that I found in a "1981 Cadillac Digital Fuel Injection and Computer Command Control Diagnosis Manual Supplement" manual that I purchased for future use with my 81 Eldo it says you can get the Check Engine light to flash the trouble codes by jumpering pin D to pin E (ground) on the Assembly Line Diagnostic Link (ALDL) connector located below the dash on drivers side near the steering column (faces straight down). So if your Fuel Economy display won't work I would give this a try. I haven't tried it on mine but I did use the same connector to verify that my Check Engine light was working properly using a separate test from the manual. Only tricky thing is to use the correct pins as you need to view the connector from the floor upward and it can be confusing when the drawing shows it in a straight on view. It took me a couple of minutes to be sure that I had the right ones.
Hope this is helpful. Dave
Update; purchased a replacement computer and car is running great until today; got trouble codes 17 and 23, does anyone know what they could be from?
My 81 manual is still missing and those codes don't appear to have existed in 80 so I don't even know what they are. I just got one more idea where to look for the 81 manual. Silver cover right? I know the 80 is blue because I found that.
TJ,
Dave Dunlop posted a picture of at least the Electrical Troubleshooting manual on another thread (It does appear to be silver). He doesn't have a lot of posts but he also contributed to this thread. Maybe he will be able to find the trouble codes in the Troubleshooting manual?
Anyway this link should go to page 13 of Giuseppe's thread where he posted a cover photo of the 1981 manual (last 2 replies on page 13):
http://forums.cadillaclasalleclub.org/index.php?topic=156186.240
Scott
Hey tj Hopland, I just bought a 1981.eldorado 6.0....been sitting since 2002. Doesn't want to Start, cranks but won't start . I noticed the trunk has 2 ecms in it just laying there..and the ecm that's being used is just hanging down underthe glove box smh..can you help explain to me why you think this was like that? What were they trying to do? Any info would help thanks!
Jonathan,
Welcome to the forum.
If the car has been sitting for over 20 years you should probably start with the basics. My first thought is fresh gas. You could see if it fires with starting fluid. If it does not check spark. It could as well be timing.
Scott
If the 'running' one wasn't hanging loose you could maybe just hope that someone was collecting spare parts but with the running one hanging loose it seems more likely that someone was trying to solve a problem and apparently wasn't successful.
I too say start with the basics, many people blame the computer and ignore the basics it takes for any engine to run. Check for spark. With an electronic car you don't want to just yank off a wire and see if it jumps somewhere. You want to us a real spark tester or at least a spark plug and make sure its well grounded and stays grounded. An inductive timing light is also a reasonable way to check. If you got spark then we move to fuel. If no spark we can start looking deeper into that side of things.
If you have spark then look and see if you can see fuel squiring out the injectors. The injectors are in those 2 pods hanging above the throttle plates. If no try dumping a little in or some starting fluid and see if it fires a bit. If it does then we can go down the no fuel path. If there is something squirting out but no fire try and catch some and see if it is actually decent gas. You may be trying to invent a car that runs on water.
The first thing to do is get the old gas out of the fuel tank.
When you turn the ign to run, the fuel pump should run for about 2-3 seconds. If it does, that part of the ECM is working. If you don't hear it run, get out the manual and find the 12V B+ wire color at the connector in the rear for the fuel tank. Check if the ground for the fuel sender and pump is in the connector. Run a jumper from the battery B+ to the B+ fuel pump wire at the connector. Either back probe the connector or unplug it to make the connection. If the tank ground is in the connector, you will also need to provide a jumper to ground. When you make the connection, the fuel pump should run continously. If it does, pull off a rubber line and use the fuel pump to empty the tank. If it does not run, the fuel pump is bad and you will need to drop the tank and replace the fuel pump.
Once you have the old fuel out of the tank, install a new fuel filter, take the fuel line off of the throttle body, put a rubber hose on the line and run it into a gas can, and if the ECM is OK, turn on the ign key and it should pump fuel for 2-3 secs. Do this to flush out all the old fuel and varnish in the lines. Put some Chevron Techron in the fuel tank, reinstall the fuel line and cycle the ign key to prime the fuel system.
Have someone crank the engine and watch for fuel to spray from the 2 injectors in the throttle body. If it sprays fuel, the ECM is seeing a crank signal from the Crankshaft Position sensor and that circuit is OK. If it doesn't spray fuel, disconnect the inj connector and use a noid light plugged into the harness to check if the ECM is trying to fire the injectors. If the light flashes, the injectors are either plugged or windings are bad.
Take a DMM in the ohms setting and touch the leads together to get the resistance in the leads, usually 0.1-0.2 ohms. Now measure the resistance between the two pins on the injectors. I'm not sure of the exact resistance, memory fails, but I think these were around 0.7-0.9 ohms. If the reading is 0 the winding is open. If very high, winding is bad and you need a injector.
Once you have fuel delivered from the injectors, pull a plug wire off a spark plug and install a spark tester on the wire and crank the engine. If you have spark, great. If not, you need to check the ign. system. If you have spark, the engine should start.
If it still does not start, pull the plugs, check them and if not fouled, squirt a couple of shot of oil in each cylinder and crank the engine over with the plugs out. If it has been sitting as long as you stated, the rings may have dryed out and the oil will help seal the rings and build compression.
If you have fuel, spark, and compression and it still won't start, the timing chain may have jumped time and that's a more involved diagnostic.
I hope this helps in your trouble shooting. I know its long and involved, but I don't want you to put any more of the old fuel through the fuel system than possible, because it can damage your injectors and you are also verifying some of the ECM circuits and sensors. I know I missed some things, but get started on it and if you have any questions, just post and I will try to help you along.
Well done.
Hi Johnathan, the 81 V864 engine uses one of two different ECM's depending on when your car was built. Early models used PN 1224760 and later production cars (after Broadcast # 616866) used PN 1225120. The Cadillac Serviceman Gold Book indicates that they are not interchangeable due to "emissions and driveability requirements". They also use different EPROM chip versions that are also not supposed to be interchanged. This may be why you have more than one as most people wouldn't expect two different parts in the same model year. As these are a critical one year only part to have for this car anyone finding a parts car would likely grab whatever was on any 81 in the scrap yard. Also the chips are specific to the car model with the de Ville and Fleetwood models using a different version even though they have the same engine.
One thing you could test to see if it is working is the on board diagnostics that were built into these cars. If you don't already know you can press the Off and Warmer buttons on the climate control head at the same time and hold them down for a few seconds and then release them together (with the key in the Run position - car doesn't have to be running for this test) and the temperature display should go to ".." and then "88" then display any trouble codes (a number between 12 and 80) repeat these numbers (if any) and then go to "70" which is a decision point to move to other tests. You can then reset the display back to normal operation by pressing any single button on the climate control display. This would be a good test to see if the ECM, climate control and mileage display are working properly. There are other tests you can do with the diagnostics display to determine throttle position, MAP and BARO sensor readings, coolant temperature, O2 readings etc. but most of these are only useful once you have the car running. Let me know if you need more info and I can scan a few pages from the Manuals for you. Good luck. Dave
Dave do you have any other numbers that may help him guess which ECU or Prom may be the original/correct combo for his car?
Has your research lead to to believe that using the 'wrong one' will prevent the engine from running? On later models engine would usually run but other things may not work.
I'm just wondering if maybe this car had some issue not related to the ECM and someone blamed the ECM and swapped it so even if they eventually fixed the real issue it still won't work?
Hi TJ, I don't know for sure whether the different ECM Part # would prevent the car from running or not. Looking at the Electrical drawings or in the original Factory Service Manual I don't see any notes regarding the two versions, this is only shown in the Parts Manual that I have (July 86) and also in the Gold 1981-1983 Cadillac Serviceman Bulletins book from Mar 83. Given the way it is described I am guessing that it likely would run but maybe not meet emissions requirements or have the best engine driveability as seems to be described in the Serviceman bulletin.
The change was made after Broadcast Number 617927 for the Eldos and 691350 for the Sevilles which I believe is the last 6 digits of the VIN #. My guess is that the previous owner either collected the extra ECM's "just in case" or maybe was having issues with the car and was trying different ones to see if it would correct them. As you know the ECM controls the injectors, timing advance and fuel pump relay so if there was a major problem with it it could definitely prevent the car from running. I do think that the basic troubleshooting outlined earlier in the thread would be the first steps to take to see if the owner can even get it to fire. Dave
I was just thinking if this was an early car and there was a major difference like say they changed the pin numbers to the injectors early vs late and and there was a bad crank sensor preventing the injectors from working. Someone changed ECU's so now they had 2 problems, no crank signal and now no connection to the injectors. Even if they eventually found the crank sensor issue they now have a new issue that they swapped late vs early ECU.
This was just made up stuff to show an example of something that could have happened, not real specific issues or troubleshooting for this car. Its just the kind of thing you have to think of when you don't know the exact chain of events that lead to where you are now.
Yes I agree that the current process should be to just do a evaluation of the basics and see what is working and not. If there is spark and or the injectors can be heard clicking (or are actually squirting something) the computer probably is working enough that the engine should run as far as the computer is concerned and its going to be a more basic issues.
Dave,
Does your book give the PNs? This car apparently has one "hanging from under the dash" and two in the trunk. Maybe in parallel to checking the normal-car-stuff the PNs of the ECMs could be "sorted" meaning we could tell which version should have been in the car and if it's still one of the three. We could also tell what diversity of PNs exist within the three.
Something like TJ mentioned could have happened but my thought is start by trying to get what should have been in it back in it and then work through the issues. If there's only one of what should have been and it's bad that's a different story. At least then though we would know what the other ECM should be in and how far off they are.
There could have always been some normal car issue as well. Maybe the ECU was never the problem. I guess that's wishful thinking but one distinct possibility is something else is could also be preventing start after sitting as long as it did.
Scott
Edit: I think there was another topic a couple of years ago where ECMs were listed. I recall trying to go through the list to help someone. If that list didn't already come from Dave maybe I could find it. I think that was an ECM which was damaged by high current due to a sticking solenoid...
Hey thanks for all the help, I started a new forum the correct way under technical, it's titled 1981 eldorado 6.0 fuel issues, so any info over on that forum would be really helpful. So a couple quick things, I did get it running for a few seconds with starting fluid and it ran great! ( for those 8 seconds). I did get the old gas out and put a new rubber hose and replaced the fuel pump as well. I'm very confident in saying I don't think it's my spark or timing due to the fact I have zero fuel pressure. It almost seems like the computer isn't telling the relay to turn on or something along those lines. But I ordered a service manual and it should be here on the 1st of this coming month. But anymore info will help thanks everybody a bunch!