89 b2200 check engine light

hey i dont know wuts up with the check engine light, it doesnt just stay on like alot of post ive read it only comes on while running at a constant rpm/speed. if i accelerate or decelerat at all it goes off. down the hywy or just doin 40 down street as long as it doesnt fluctuate its on. any one know or heard of this if so i just would like to know wut it is or could b so i can take care of the problem. few facts about the truck are its got 150k 5sp, no power anything, runs decent, not much uuuumph, dont burn oil or smoke, thats about the long and short of it, so any info will b appreciated

MIL lights can be transient. You need to get the error code from the computer. The light might be on while the error is happening, then the condition goes away, so the light goes off. As a point, for my 91 B2200, the closed loop running errors only occure at 1500rpm or higer. Thats the only time the FI computer looks at the O2 sensor for closed loop running and error reporting(my truck is FI). I don't know if the '89 is the same or if your truck is carburated(which may make it different).

RussC

thxs for the info rus now how do i go about getting the error code? I assume it is some letters and or #s (the error code) how do i find out wut they mean? but once again i appreciate your help.

Ground the green connector in the engine compartment near the fuel filter on the passenger side. It's one wire conn. that brown with colored dots(can't remeber the dot color). Then put ingition to the run position. The check engine light should illuminate, then turn off, then start flashing error codes(if any).

RussC