: Service soon engine light



nfakbc
11-11-09, 03:06 PM
I searched this forum/ looked in the FAQ section above and cannot find a answer to my question. My car is a 1984 coupe deville. I have a service soon light on but cannot pull any codes to try to figure out what is going on. I've tried a obd1 scanner tool which says it cannot connect to car, have jumped the 2 pins on the connector which just turns on a solid service now light (no flashes at all) and have tried through the climate control with no luck.

I've tried a different engine ecu which came out of a perfectly running car with no change. Anything else I should look for to fix my obd problem? Thank you in advance.

greencadillacmatt
11-11-09, 04:36 PM
Is the light on constantly, or is it on sometimes and off sometimes? I have heard that the service engine soon light comes on when there is an exhaust emissions problem that may or may not resolve itself. I actually have a 1984 Coupe DeVille, and the Service Engine Soon light would come on sometimes, and stay off others. What engine is in yours? Is it the HT4100, or is it the Oldsmobile 350 Diesel? Good luck with the 2-Door! :p

csbuckn
11-11-09, 07:14 PM
We had the same problem on an 84 Deville and a Suburban and it turned out to be the fuse to the computer. We replaced the fuse and was able to read codes after that. Maybe its the same issue for you. The fuse should be with the rest of them under the dash

nfakbc
11-11-09, 10:57 PM
I will definately check out the fuse. My motor is the 4100 gas.

drmenard
11-11-09, 11:35 PM
If my memory serves me right.... Press the off and warmer buttons at the same time on the CCM. and hold till... all segments should light up 88.... then it will flash the trouble codes... If you need help with the codes , post them here...

Slacker
11-13-09, 03:56 PM
If my memory serves me right.... Press the off and warmer buttons at the same time on the CCM. and hold till... all segments should light up 88.... then it will flash the trouble codes... If you need help with the codes , post them here...

This.

Just adding that on my '82 the buttons are pretty worn so getting a good contact with the "off" and "warmer" while holding took a few tries. I didn't believe that this was the way to do it for a few weeks when I first got the car. :)