OK. I searched for hours on here about vss issues. I swapped the engine about 6 months ago (y8 had 285,000...rip good friend). Got a z6 pretty cheap with 80,000. p28 ecu. All engine grounds are good. I put a new alternator in just because I am pretty sure the old one was stock.

My speedometer and odometer quit working about 4 years ago....well, it worked at times.....I would drive for 10 minutes and it would be on the whole time. Next day didnt work. Next day would work.

So, last night I put the new vss in, plug it in and take off down the road. Spedo doesn't work and the lights get dim and then bright, car ran rough....back and forth. I unhook plug everything is fine...except it throws a cel.

So I am assuming a short in the harness or something? Could it have anything to do with the swap?

I drive this car everyday and just want to make her a perfectly reliable car...not a bitchy bitch that gives me nothing but trouble.

 

Check the wiring and VSS connector, they often get oil in them and make bad connections and crack as well.

 

I cleaned everything with contact cleaner. No cel light....no speedo either. Now can a faulty vss cause the speedo itself to go out? The needle bounces sometimes like it wants to work. About ready to give up on the speedo.