VSS and Speedometer

Archaic2021

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I have a 97 5.0 2wd. The speedometer is reading really fast. According to gps speed is 30 the speedo shows 55.

I check the vss with my scanner and the scan tool shows accurate with gps..so does that mean my cluster is gone or could that still be the vss.

The tires are the correct size, and to my knowledge the rear end is correct.
 
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kennythewelder

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How long have you had this truck? Is this something that just started out of the blue? It could be the air core stepper motor for the speedometer. You can order one on line, but who knows if you get the rite one for the options you have. Your next option would be to have the ECM recalibrated to read correctly.
 

Schurkey

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How long have you had this truck? Is this something that just started out of the blue?
Good questions.

It could be the air core stepper motor for the speedometer. You can order one on line, but who knows if you get the rite one for the options you have.
My limited experience with stepper-motor gauges is that they don't read a percentage of "correct"; they read way-out--and then die there. So, the speedo might read 55 instead of 30 one time, but it'll then die at 55 and be stuck there until you pull the dash apart and solder-in new steppers.

Does a '97 have a stepper-motor instrument cluster? I'm gonna have to find this out some day--I own a '97 K2500. I know that '88 is too early.

My '03 Trailblazer has steppers; I had to replace them over ten years ago.
 

Archaic2021

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I just got the truck from my Grandfather who just passed away. He has owned it for about 5 years and bought it from the original owner.

I'm not sure how long this has been going on as it has just been a yard work truck/driven very occasionally.

I plan on doing a new plugs, wires and give it a good drive
 

Archaic2021

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Just to update this the rpms is also reading way higher..i thing the cluster is shot.
 

PewterK1500

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I’m having the same issue with my 98 K1500 4wd VSS to the dash command app through elm 327 is accurate with gps reading. When I’m going 62 MPH the speedometer reads 70 MPH. Previous owner swapped in a GM Performance HT383 and had a fastchip tune done to the pcm at one point. I wonder if the vss sends the signal to both the pcm and the speedometer or if the pcm sends the signal to the speedometer after it receives it from the vss.
 

Schurkey

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I'd be looking in the service manual.

I wonder if the vss sends the signal to both the pcm and the speedometer or if the pcm sends the signal to the speedometer after it receives it from the vss.
Back in the '88 model year, the VSS fed the instrument cluster directly. The cluster modified the signal for use by the cruise, ABS, and engine computer; and also fed the speedo and odo.

But that may not be true for newer vehicles. The service manual will have the wiring diagram and description.
 

yevgenievich

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From what I was finding, the air core motors in the clusters start to fail giving wrong indicators. Last time just replaced the cluster, this time planning to replace motors only
 

stutaeng

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My 00 K3500 5.7 is the same way, but opposite: I need to drive 77 mph to the cluster to actually drive 70 mph. The ECU reports within 1-2 MPH of GPS.

I just drive it like that...I haven't tried swapping clusters, but I suspect that's the culprit.
 
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