just got my 4.9 out of a 92 eldo put in but hooked a scan tool to it and the scan tool says there is no communication to the ecm did i wire the aldl wrong or am i missing something for the diagnostics would be thakful for any help on this

Anyone have any input on this? I am at a loss on it too.

Are you sure your scan tool is able to communicate with an OBDI computer? Make sure its set to VIN 4th position C, 8th position B. If that doesn't work then recheck your wiring to the ALDL.

Yes, it will work on anything with a computer up to 2001. That is what I have the chips for anyway. It is a Snap On brick.

Did you wire it as such (viewed from the front side)?


Try scanning it as different year 91-93. Have you changed the chip in it? How did you wire it up (DeVille, SeVille, Fleetwood, etc)?

I know some people have had some problems with scanning thier 4.9 - but non eof them had actually gotten back saying if they figured the problem out or not. Could be that the scan tool is not compatiable with the 4.9 (it must be OBD1 compatiable - basically if it comes with the correct cable to fit the plug, then it is fine)?

Also in the Caddy diagrams, there is a jumper between 2 of the pins on the ALDL plug - it could be that this scanner is looking at the jumpered pin vs the 1 in the diagram I posted (I do know that diagram I posted works fine on a couple different scanners, but can not comment on them all).

Hope that helps and please keep us posted on what you find.

I believe Rockcrawl uses a snap-on scantool. That one should work. I use an Autoxray 3000. Picked it up for 100 shipped on e-bay.

I also added the jumper for the second pin in the aldl so I have no idea which one my scanner is using. Wired just as listed in the pinouts on bottom of this page. Ignore the DERM part. Its not necissary. I scan as a deville/fleetwood, 4th vin digit "C", 8th digit "B". If you wired as a seville/eldorado so a google search for "91 seville vin" and you will get the digits you need. Good luck to both of you.

[This message has been edited by Fieroseverywhere (edited 08-18-2008).]

will check my wiring and check it again thanks for the help will keep everyone up to date on this

thanks for the help guys jumping the wire from A8 to both aldl connectors M & L fixed the problem but you do have to use C as the 4th vin on the scanner