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1981 Eldorado 368 8-6-4 code 18 ECM FRIED

Started by Tonyv_73, June 13, 2017, 10:02:23 AM

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Tonyv_73

Okay so just to clear up my issue, my car runs pretty much perfect, I drive it with the 8-6-4 plugged in, almost every time I drive the car my check engine light will go on and code “18” will show up in the computer. I reset it and sometimes it will go away and sometimes the code will come back. What should I look at in reguards to the engine? I had a tune up done on the car which included cap, rotor, plugs, wires, etc.  I should also note the only other issue with the car is when I get gas the gas spits back up the neck. I assumed that the sending unit will most likely need to be replaced because the tank is not getting ventilated.  I am only mentioning this in case it has some connection to the code 18 issue.  Also I have not changed the injectors so if that helps let me know.
1963 Series 62 Convertible
1965 Eldorado
1966 Calais Sedan
1970 Fleetwood Brougham
1970 Wildcat
1970 Coupe Deville
1973 Eldorado Convertible
1974 Coupe Deville
1976 Coupe Deville
1981 Eldorado Biarritz
1985 Eldorado Commemorative Edition
1991 Brougham
1993 Eldorado 4.9
1996 Fleetwood Brougham
2006 XLR
2006 DTS
2014 XTS

smokuspollutus

Tony, as was mentioned this code has nothing to do with mechanical parts, so I would disregard the tune up as a possible cause. When you turn the key all the way forward to crank the engine, a reference signal goes to the ECM. Unlike a lot of the wiring going to it, GM thoughtfully included a fuse on this circuit. Check if you have 12 volts to this circuit while cranking, then check the fuse. My bet is they will both check out ok, and the problem lies in a bad connection on the ECM. Clean up the contacts and re-seat the it.

Dave Shepherd

Interesting about the stalling issue, at that time when I worked for Cadillac in NYC, we had multiple complaints about stalling, very hard to reproduce, but one common cause was the baffle in the gas tank that the pick up sat in broke loose and  would block the fuel flow under certain conditions.

jsanford

Tony,

Amazing how any time someone has any sort of trouble with a L62 equipped car the comments instantly go to what a disaster the engine was  ::)

I have attached the trouble tree from the SM so you can give it to your mechanic. Good luck getting it sorted out.

Jeremy
Jeremy
Sacramento, CA
1980 Seville
1981 Eldorado
2016 ELR

Eric DeVirgilis CLC# 8621

Quote from: e.mason on February 03, 2018, 10:13:36 PM
https://www.leagle.com/decision/198350593nj412184

http://caselaw.findlaw.com/ca-court-of-appeal/1770877.html

https://www.newspapers.com/newspage/6380730/

Thanks for the detective work. (I only said I have no recollection; not that it did not happen.)

If any car deserved having a lawsuit being filed over, it should've been the HT4100.  :o

Quote from: jsanford on February 04, 2018, 11:03:59 AM
Amazing how any time someone has any sort of trouble with a L62 equipped car the comments instantly go to what a disaster the engine was  ::)

Indeed. 
A Cadillac Motorcar is a Possession for which there is no Acceptable Substitute

TJ Hopland

Since there is a fuse in that circuit I would check that close.  Recently on a much newer vehicle with that style fuses I had intermittent issues that turned out to be what looked like tarnish on the fuse blades itself.   I say tarnish because it didn't clean off with a wire brush like normal corrosion.  Slapped in a new fuse and all was well.  The socket looked fine. 

Its interesting that they put that fuse where they did.   I wonder if that is maybe to protect the wire when it comes inside the car vs under the hood?   There isn't likely much of a load so it won't take much of a bad connection to screw it up.

Where is that '56 way' physically located?     
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Tonyv_73

Just drove my car to get lunch, when I finished and started my car I was idle for about 10 minutes and I got a bunch of codes

19
23
24
25
32
44
45

I looked them up and they’re all pretty much from a short, anyone have any suggestions as to where this short could be?
1963 Series 62 Convertible
1965 Eldorado
1966 Calais Sedan
1970 Fleetwood Brougham
1970 Wildcat
1970 Coupe Deville
1973 Eldorado Convertible
1974 Coupe Deville
1976 Coupe Deville
1981 Eldorado Biarritz
1985 Eldorado Commemorative Edition
1991 Brougham
1993 Eldorado 4.9
1996 Fleetwood Brougham
2006 XLR
2006 DTS
2014 XTS

TJ Hopland

Its really unlikely to have that many codes that are not related so you have to find out how they are related.  Start by finding what all those codes / sensors have in common.    Do they all have a common ground point perhaps?   All run into the same loom?   Same bulkhead connector?   Same connector at the ECU?   

I have not looked at them for a while but I remember the electrical parts of the service manuals in that era were pretty well written since at the time no one was used to dealing with the computer stuff.   They gave a very specific sequence to trouble shoot which if that doesn't solve the issue on its own would give you indications how the things relate to each other.   For instance the first like of say code 99 would be to make sure you don't have a code 77, if you have a 77 fix that first.  That would tell you that what ever sensor or module 99 is likely depends on 77 working correctly. 
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Glen

After troubleshooting multiple codes on the “02 Buick antilock brake system, I removed all the grounds, cleaned and replaced them.  No more trouble codes.   Maybe you could try that. 
Glen Houlton CLC #727 
CLCMRC benefactor #104

Tonyv_73

I am posting on this thread because i just realized there may be a connection.  I recently posted a thread about how my ECM fried, heres the original post...

"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."

can someone who has knowledge on these computers let me know if theres anything that can be done?

also, I recently found a post from 2008 where someone unplugged the "Air management Valve Solenoids" from the 81 6.0 enigne and the ECM stopped the smoking.  I did the same thing and had the same results, with the Air management Valve Solenoid unplugged the ECM did not smoke.
1963 Series 62 Convertible
1965 Eldorado
1966 Calais Sedan
1970 Fleetwood Brougham
1970 Wildcat
1970 Coupe Deville
1973 Eldorado Convertible
1974 Coupe Deville
1976 Coupe Deville
1981 Eldorado Biarritz
1985 Eldorado Commemorative Edition
1991 Brougham
1993 Eldorado 4.9
1996 Fleetwood Brougham
2006 XLR
2006 DTS
2014 XTS

Tonyv_73

Hey, Still trying to resolve this issue, ECM completely fried,  bought a new one and reseated connections, bought new PROM chips (same part number) . still cant find the short.  where do it start???
1963 Series 62 Convertible
1965 Eldorado
1966 Calais Sedan
1970 Fleetwood Brougham
1970 Wildcat
1970 Coupe Deville
1973 Eldorado Convertible
1974 Coupe Deville
1976 Coupe Deville
1981 Eldorado Biarritz
1985 Eldorado Commemorative Edition
1991 Brougham
1993 Eldorado 4.9
1996 Fleetwood Brougham
2006 XLR
2006 DTS
2014 XTS

TJ Hopland

I would open up the fried units and see if I can get any clues as to which system(s) have the issue.   Look for burnt stuff and see if you can tell which pins in the connector they go to.   Use the diagram to figure out what sensor or systems are connected to those pins.    If you can't tell then you may have to just go pin by pin.     

With the electrical service manual you will know what is hooked each pin and you should be able to do basic ohm meter tests to determine if what is connected to it is shorted to power or ground and often the general health of the system.

Again I would be looking for visual clues to save time by looking at the fried units and carefully inspecting all the wires and connectors I can see.   Look for places that don't look factory.  Look at places with heat like around exhaust.   Look for places that are more exposed to road grime like down to the starter.    Its pretty rare to have a wire or connector just fail for no reason at all.     
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Tonyv_73

Quote from: TJ Hopland on February 17, 2020, 01:15:47 PM
I would open up the fried units and see if I can get any clues as to which system(s) have the issue.   Look for burnt stuff and see if you can tell which pins in the connector they go to.   Use the diagram to figure out what sensor or systems are connected to those pins.    If you can't tell then you may have to just go pin by pin.     

With the electrical service manual you will know what is hooked each pin and you should be able to do basic ohm meter tests to determine if what is connected to it is shorted to power or ground and often the general health of the system.

Again I would be looking for visual clues to save time by looking at the fried units and carefully inspecting all the wires and connectors I can see.   Look for places that don't look factory.  Look at places with heat like around exhaust.   Look for places that are more exposed to road grime like down to the starter.    Its pretty rare to have a wire or connector just fail for no reason at all.   

I've opened up the unit and I saw where the burnt area is however I am not an expert at tracing circuts to get to the pin.  Ill do my best and update soon with anything I find
1963 Series 62 Convertible
1965 Eldorado
1966 Calais Sedan
1970 Fleetwood Brougham
1970 Wildcat
1970 Coupe Deville
1973 Eldorado Convertible
1974 Coupe Deville
1976 Coupe Deville
1981 Eldorado Biarritz
1985 Eldorado Commemorative Edition
1991 Brougham
1993 Eldorado 4.9
1996 Fleetwood Brougham
2006 XLR
2006 DTS
2014 XTS

Tonyv_73

1963 Series 62 Convertible
1965 Eldorado
1966 Calais Sedan
1970 Fleetwood Brougham
1970 Wildcat
1970 Coupe Deville
1973 Eldorado Convertible
1974 Coupe Deville
1976 Coupe Deville
1981 Eldorado Biarritz
1985 Eldorado Commemorative Edition
1991 Brougham
1993 Eldorado 4.9
1996 Fleetwood Brougham
2006 XLR
2006 DTS
2014 XTS

Tonyv_73

really need help with this: 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?
1963 Series 62 Convertible
1965 Eldorado
1966 Calais Sedan
1970 Fleetwood Brougham
1970 Wildcat
1970 Coupe Deville
1973 Eldorado Convertible
1974 Coupe Deville
1976 Coupe Deville
1981 Eldorado Biarritz
1985 Eldorado Commemorative Edition
1991 Brougham
1993 Eldorado 4.9
1996 Fleetwood Brougham
2006 XLR
2006 DTS
2014 XTS

Tonyv_73

Replaced the solenoids and ecm, car runs good now but I just got a code 17 and 23; anyone know what they mean?
1963 Series 62 Convertible
1965 Eldorado
1966 Calais Sedan
1970 Fleetwood Brougham
1970 Wildcat
1970 Coupe Deville
1973 Eldorado Convertible
1974 Coupe Deville
1976 Coupe Deville
1981 Eldorado Biarritz
1985 Eldorado Commemorative Edition
1991 Brougham
1993 Eldorado 4.9
1996 Fleetwood Brougham
2006 XLR
2006 DTS
2014 XTS

TJ Hopland

Wheew.....  I'm not loosing my mind,  there is more than one thread and many of the posts are duplicates.   I knew I was mixing this up with the Italy one which was confusing enough but now that I see there are 2 of these I feel a little better.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason