90 allante no ecm data and lighting osm issues
 

hey all. i am a professional mechanic that specializes in Cadillacs and still cannot figure this car out. this is my personal car. so here is the beginning of my dilemma, i bought the car from a customer of mine because he was done with it. its in great shape. my issue is i have no ecm data. i have a factory 1991 service manual. i went through the trouble tree and everything checks out it told me to replace the ecm or calpak i did both twice! it was running great but now i have a runability issue and cant figure it out since i have no data. i cant even use my old snapon brick (old scanner for these) it doesnt give me data. so there is that. now i think its related to my lighting issue. the ccdic gives me the codes L202 and L203 which is osm#2 and osm#3 communication problems. looking at my manual it tells me where the osms are but its missing osm#2 there are no wires or osm for it. so i unpluged the supposedly osm #3 and i got a code for osm #6 so my book is totally wrong. the car tells me all the tail lights and turns lights are out but they all work. what i think is going on is osm #2 or 3 are pulling my data line down. i have tested for power in everything! i also replaced the bcm a while back because the trouble tree for the light issue told me too. im stuck here. does anyone have the factory 90 book? i used mitchell and alldata but all the same info from the 91 book was what they had. sorry for the long post but im going nuts here!! has anyone had a similar issue for the ecm data or osm issues?

You Could try to pm stealth He's a Allante' guy. Scanners don't do well with DFI. What isn't working beside no ecm data? What happens when you try to get into on-board diagnostic? Unless you actually have a lighting problem I would not worry about lighting codes...many have the intermittent lighting codes and no issues.

you do need a FSM for that yr .. i see them on ebay .. here are some under $40 ... click on the next line/link .. it should take you there ...

factory manual allante 1990 | eBay

as to the lights, you need to check each one for correct part number AND the cars do not like zinc coated bases on the bulbs .. get all brass base bulbs with correct part numbers .. see my 'xyz allante facts' ..

as to the on-board computers/OSMs, i have seen many many e-ghosts problems solved by simply disconnecting, cleaning, and applying dielectric grease to connectors...

is the onboard DIC operational? any codes?

good luck ...

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nice to see u here slowroll .. its been awhile ...