Service engine soon light

Caprice estate 1990 olds 403/700. My service engine soon light has a life of its own! as soon as i turn the ignition on the light comes on like it is supposed to, but it is still on when the engine is running, and it is still on even if i disconnect the ecm with the engine stopped, I tried to do the paperclip trick to get the codes but the light is not flashing, its just on.

Does anybody know witch of the wires at the ecm that goes to the ses light , i need to cut it and connect a testlight to see if the problem is in the light/cluster.


Thank´s Sigge!

Did you put the 403 in it? I would suspect that the conversion may have deleted the function of the CEL.

It has all the emission parts from the 307 and the previous owner drove it for a couple of years without any problems with the f-----g service engin soon light

The 403 and the 307 are the same enginefamily. this 403 has a 0,30 overbore, forged pistons shaved heads, a hotter cam, headders, and a modified rochester carb but it still cleared the emission test every year.

Sigge!