New owner of a 1998 Tahoe, 5.7lit with 270km.
The tachometer shows roughly ~15%-20% higher rpm, i.e. when idling at 600rpm indicates 800. Verified via computer while running. The Speedometer indicates 140Km/hr when i am actually traveling at 100Km. Verified via computer and GPS.

I even verified that the trip meter etc is correct.

I also verified that nothing is plugged inline to the computer, looks stock. It is only the 2 gauges that are out.

What could be the cause of this issue?

 

Anyone?

 

Sounds like maybe a prior owner changed the gears and/or tire size at one point and either did not get it re-tuned or used a handheld programmer and removed the tune prior to selling the truck.

 

From a computer point of view everything is correct. I have verified that by a third party.

 

I don't know if this style of truck is affected by the stepper motor issue, but if so, I would suspect that.

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