1991 GMC 1500 Pickup Q&A
1991 GMC 1500 Pickup Question: Wheres my tach. sensor located on my 91 gmc 1500 sierra?
what else is jumping besides your tach? Engine? In other words is tach a reflection of how engine is really running or is it doing it's own thang? That answer will determine what needs to be serviced/replaced. - ziptie12
would not necessarily call it a tach sensor, sounds like the instrument cluster is bad. the tach signal comes from whatever the vehicle uses for rpm, be it distributor, crank sensor. obviously since your vehicle is running ok, its going to be the cluster that needs to be checked. - Dealer Diagnostics