hey guys, first post and got a really urgent question...

I have a 2003 Yukon 5.3...
Recently I cleaned throttle body and then a few days later (not sure if these are related) the tachometer got way out of wack... reading 500rpm when i was clearly going around 2k rpm.. and 0 rpm or lower at idle and sticking at 1k, going way out of wack... Is this due to me cleaning throttle body? I couldnt find out if it had to be readjusted/relearned with the idle or whatnot. I'm pretty sure the tach is from PCM which gets signal from crank sensor.. and I dont have a check engine light so im pretty sure its not the sensor.. so im going to guess that since it wasnt directly after, the throttle body was cleaned that it is not what the problem is. I would have to assume that its the pcm or the cluster (insterment panel) which would be covered by extended warranty... Has anyone ever had this problem before? Or had any problems taking throttle body off and unplugging the sensors? Also, how can I reset the pcm?

Thank you so much in advance and nice to meet you guys :P
Buzzsaw

 

I would go with the simplest, its probably a loose connection. Have you recently washed the engin or has it been washed? an arcing plug wire will casue the tach to wierd stuff.
Cleaning the throttle body should not require any relearning and is a good thing to do, but make sure you didnt knock something loose or pinch a wire when removing/reinstalling the intake assembly.

 

Also might try disconnecting the battery for a couple of minutes.