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1990 Cadillac Eldorado 4.5 PFI
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63 Posts
Discussion Starter #1
Hello all. I just purchased my 90 Eldorado with 101K on the clock. I feel very lucky as the Caddy is in excellent shape. I will post pics soon. I am a service manager for a large used car chain. My experience is mainly with Fords so I am learning a little about these Eldo's. I previously owned a 91 Coupe DeVille that I did a little work on so I know a *little* about the 4.x engines. Okay, onto my questions.
First, I flushed the cooling system, added the seal tabs,(see, I know a little) cleaned out the throttle body and egr tubes(extremely carboned up) and did a little de-greasing in preperation for new intake gaskets in a couple of weeks. So my first issue/question is this. I need to clear the check engine light that is on now. The code is E048, EGR system fault. I cleaned the EGR tubes and repaired a vaccum line in an effort to correct the condition. I entered diagnostics via the off and warmer buttons, then proceeded to clear the memory after the computer displayed the coded by pushing the OFF and HI buttons at the same time. I held them down for a solid minute and all I ended up doing was re-starting the diag process. How do I reset the memory through the on-board diagnostics with this Eldo?
Second issue/question. This is only meant to be asked as a possible common problem/solution. My drivers side rear lower stop/taillight is bright as if the brake pedal were depressed. All other lights work as designed. The rear indicator for the taillamps also shows the drivers side light bright like the brake pedal is depressed constantly and the arrow in the instrument panel almost stays on constant like a bulb is burned out(I replaced the problem bulb with a new one because one of the filaments was burned out, but same problem). I am guessing that I may have a bad pigtail for this bulb, but I am wanting to see if this is a common problem with a simple solution.
The car is great other than these two niggling issues. The aformentioned intake gaskets are leaking a little and I am going to address this concern in a couple of weeks. I will probably replace the water pump, thermostat, plugs, wires, etc. while I have it all apart, just to freshen things up and take care of future issues before they become issues. My 91 was great and I regretted selling it pretty soon after it left, so I decided that another Caddy was in order. I really like the older Eldo body style with the 4.5PFI or the 4.9PFI and was lucky enough to come across the one I bought in amazing condition. This site is great and I am happy to be apart of it. Thanks in advance for all replies/help that you may provide.
 

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94 Eldorado, and a 99 ETC
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3,887 Posts
First of all :welcome: :wave:

To clear the codes you enter diagnostics mode like you did. Then when it says "ECM?" press the fan up button once. It should enter the submenu for that module. then you press the fan down button until you reach "ECM CLEAR CODES?". Press the fan up button to clear the codes. It should display "ECM CODES CLEAR" before taking you to the next option in that submenu. You can turn the key off to exit diagnostics mode.

In diagnostics mode:
fan up = yes
fan down = no/next
off = back
key off or reset button = exit diagnostics mode

I'm not sure about the other stuff you mentioned. Maybe someone else will chime in for that.
 

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2000 Polo Green Metallic Cadillac STS 60K
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787 Posts
As far as your taillights go, try replacing your tail lamp harness. I had a 94 Deville that had crazy taillights like you described and turned out the wire harness was shorted out. You should be able to pull one from any caddy within a few years of yours if you cant find the harness new. The harness is plug n play so installation is a breeze. You can also check your brake switch under the drivers side dash and see if its functioning correctly. The brake switch is very inexpensive so your ok in that department.:thumbsup:
 

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1990 Cadillac Eldorado 4.5 PFI
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63 Posts
Discussion Starter #4
Thanks for the replies.:thumbsup: Through trial and error this morning, I figured out how to clear the codes. I was thinking much along the same line as far as the wiring harness. The more I though about it a bad pigtail or harness seemed to be the likely culprit. I'll check out a couple of the local yards this weekend for a harness. I'm guessing anything out of a 86-91 would work, right? Thanks again for all of the help/suggestions.
 

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eldorado
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125 Posts
Also on the bulb issue pull it out and look at it to dee if someone jame it in and screwed up socket and try switching bad bulb with a good one to see if filament isn't bad , Sometimes they will blow and filament will weld itself to the wrong place in the bulb..i had a vett that the alt power surged and screwed almost every bulb and all lits in rear did the same prob you are haveing ..
 

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1990 Cadillac Eldorado 4.5 PFI
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63 Posts
Discussion Starter #6
Thanks for the tip EldoDave. I did just that last night when I was doing a little light troubleshooting. Didn't solve the issue, though. I am leaning towards the harness/pigtail issue at this point, but I am going to look at it again tonight to verify that is the problem. Thanks for the help.
 

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1990 Cadillac Eldorado 4.5 PFI
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63 Posts
Discussion Starter #7
Ok, so last night my dome/courtesy lamps were all working fine. Today, no lamps. They will turn on with the thumbwheel on the dash. No dice when opening either front door. I find it hard to believe that both door jamb switches went bad at the same time. Are these wired to only come on when the twilight sentinal sences it is dark outside? One more thing to figure out now.:bigroll:
 

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1990 Cadillac Eldorado 4.5 PFI
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63 Posts
Discussion Starter #8
Just an update for any following along. Dome/courtesy lights started working last night when it got dark out. Didn't work this morning with plenty of light. My guess is that they don't come on unless the twilight sentinal senses it is dark outside? Anyway, I can live with that. Now to get the rear taillamp working right! Thanks for all of the help.
 

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1926 Model T street rod, 2000 Jaguar XJ8, 1999 Corvette.
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6,738 Posts
Common problem with the bright bulb is the socket itself. They corrode or the ground side wire becomes ill fitting within the socket causing feed back thru the wiring. This would cause a dimmly lit arrow in the dash cluster because of a weak or non existing ground to this socket. Interior lights only work when needed. Daytime no lights, dark outside, dome lights. Be careful with the intake gasket job. The intake manifold mates with the cyl head under the valve covers, much like an old 460 Ford. You MUST retorque these bolts EXACTLY like the service manual directs or you will warp the engine block or damage threads in the block.
 

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1990 Cadillac Eldorado 4.5 PFI
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63 Posts
Discussion Starter #10
Thanks for the tip carnut. I run a service department so I have an account for alldata. I looked up the intake gasket job to get an idea of what I am up against. I am definately going to make sure that the bolts are torqued exactly the way that GM says to do it. I did the intake gaskets on my 93 Explorer 4.0 and they are a similiar design with having to pull the valve covers off to get access to the lower intake. The intake is only leaking oil externally right now, so I will probably wait for a couple more weeks to do the work. Don't want to be knee deep in intake gaskets on memorial day weekend:alchi:. Thanks to all for all of the tips/help so far.
 

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1926 Model T street rod, 2000 Jaguar XJ8, 1999 Corvette.
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6,738 Posts
Common for oil to seep at the ends. I've had luck on a couple by cleaning this area with brakekleen then applying black silicone where it seeps. Leave it alone overnight. As you know this is only a nuisence leak
 
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