caper

the tach on my 97 while driving will just drop to nothing and then bounce back again , anyone have the same prob before????

pullmaxdude

My 96 will do the same thing, just tap the front of the gauge cluster and all is well!!

boostedte37

my 98 was doing that and I thought the crank sensor was going bad, turned out the rubber bushing in the harmonic balancer was comming out and the balancer was wobbling

1Rodeoguy

Check thae rubber bushing that boostedte37 mentioned if that is not the problem, it may be the crank sensor. I have replaced mine several times.

TxDiesel007

I did

one of two things, One the crank sensor was outta whack, take a business card and fold it in half, and reset it to about the thickness of that folded Business card, it might need readjustment from engine vibration, Two, check your batter connections, a bad battery connection could result in flickering lights and a bouncy jumpy tach, as i have learned the hard way, and the third one, of none of those do it, replace the tach sensor and u should be good to go..

Rick

gmctd

Tach sensor is the crank sensor - ECM reads the crank sensor, feeds the tach.

Make the adjustment, as suggested - if that doesn't heal it, replace the crank sensor

Dave D(SK)

Had the same problem with my 96, after spending a few hundred at the dealer and replacing the crank sensor problem still occurred. Finally got teed off enough to troubleshoot myself and found the signal wire from crank sensor to PCM had a bad spot in insulation (back near firewall) and was occasionally but regularily shorting to ground causing the tach to drop out as well as shut down charging and make a few other warning lights on the dash come on.

Replaced wire about 4 weeks ago and no problem since then.