I have a 1998 Olds silhouette and the intake manifold gasket went out and leaked into the engine. We decided to replace the engine and since the ABS, Brake and TCS light come on and off. Also the Service Engine Light comes on and off. It doesn't usually come on or off while driving, it usually picks a way to act when you start it one, two or all four lights are on and then stay on until you turn it off and then the next time it may be different sometimes all of the lights are off too. The people that fixed the engine thought it might be a sensor of some sort with the antilock brake system and would cost 800.00! these lights were not a problem when the car broke down. Any ideas? Thanks. Also since we replaced the engine the transmission shifts hard from the first to second gear.

I've had simular problems, one with a 97 Silhouette and one with a 99, both of them had blown head gaskets. I replaced the gaskets and then the red brake warning light and the TSC light started coming on. I never did get to the bottom of the 97 and now I have the 99 I'm dealing with now. I'm doing all the research I can. Hopefully someone can enlighten us or I'll eventually get it figured out and l'll let you know what I find. Billn

very common problems on these vans: Speed sensor wires at the front wheels break. I have repaired wires if there is enough to get hold on.
Also, the rough shift and intermittant cel could be caused by a dirty maf sensor. I can get more specific if need be.

800 $ is some high priced thinking on a abs sensor!!!
That is what they make scanners for.
Get it put on a good engine/trans/ABS capable scanner and it should lead you to the problem.
If you get any codes post back codes.
MT