My (new to me) 2000 Blazer speedometer seems to be reading about 50% speed. I have seen it read true speed a few times, but quite infrequently.
I took it to the local Chevy dealer recently for three issues: 1. Speedo as mentioned 2. ABS and Brake light come on sporatically 3. Air Bag light

The dealer claimed that the speedometer problem would require a replacement cluster. After reading posts in this forum and others, I ordered what I thought would be a simple fix: A used cluster. Unfortunately, the problem remains with the replacement cluster - Identically! - it leads me to believe the problem resides elsewhere.

Could a 50% reading on the speedo (and odometer) be caused by the VSS?

The ABS/Brake light issue was attributed to a faulty ABS "brain", which I also replaced to no avail . The one issue I did manage to fix, was the Air Bag light, which was the clock spring, and a fairly simple replacement.

 

That was going to be my suggestion , when the vehicle speed sencor goes bad wierd things happen . Sometimes my gauge wouldn't read at all ,sometimes it would do like your saying half speed and the transmission would shift right also .

 

*Moving thread to 2nd Gen Tech Help*

The New Member Area is for introductions only.

As far as your question goes, did you check your speed sensor? IIRC ABS takes information from there, and if it's faulty you'd be getting your speedo problem and possibly your ABS light... 2 Birds with one stone...

Good Luck

 

i agree, check the VSS.


i'd also check the wiring while you're @ it.

 

Thanks for the info, I have a friend with an identical Blazer, who is coming by tomorrow to pull his VSS, and try it in my Blazer before I order one.

As for the post in the "New Member" section, I tried to post in other sections, but was unable. Thank you for moving it.

 

really? The admins have bene playing with the new member restrictions to try and cut down on SPAM. You might have to post an intro in the new member section FIRST lol.

And hopefully you find your issue. Post up when you find out.

 

Well, I tried switching both VSS's with no luck. Mine worked fine in my friend's Blazer, and my speedo is still at half speed with his VSS's.

On to the wiring I suppose... does anyone know a proper resistance?

 

Still haven't found the problem. Even though I've replaced the instrument cluster, I'm planning to pull my buddy's cluster (knowing that it reads properly), and switch with mine as a test. If his reads half speed in my Blazer, at least I can narrow it down.

Any further suggestions would be greatly appreciated!

 

Is this truck 4wd? If so, you may have a problem with the 4LO input to the PCM which would cause the speedo reading to be dropped by the ratio of the transfer case (which for the s-series transfer cases is 2.72:1). So at 60mph actual ground speed, the speedo should read 22mph if properly calibrated to the gear ratios in the axles and the tire size.

 

I tried my buddy's instrument cluster to no avail, but I had to make sure that the replacement cluster I purchased didn't have the same issue I started with.
After confirming that's it's not the cluster, I called the dealer that initially diagnosed the problem, claiming that the cluster must be replaced. Their current claim is that the new (replacement) cluster must be reprogrammed to work properly - which they claim will cost up to $150. My question now is: why couldn't they just reprogram the original cluster?? Or is this just BS??