Tach acting up

[sdeeter19555]

Tach has been acting up lately...did a weird hang up about a year ago, then was fine. This week it reads really high one day, then really low the next. Typically starts out in the morning and afternoon commute, but after about an hour it starts acting up.

 

I've got no codes either active or stored as far as I can tell...

 

I guess my question is what are probable causes, or is it likely the stepper motor is just going bad?

 

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[jake111]

Certainly sounds like a stepper motor.  While a more common problem in the older trucks (I replaced all of mine years ago), it seems like any stepper motor can go bad.

 

If you have something that plugs into the OBDII port and displays stuff, you could watch the speedometer speeds shown there.  If they look good there, then it suggests the stepper motor for sure.