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Old 11-22-2003, 12:44 PM   #1
TB6587
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Question Code 24, VSS ??

Hi All! Newbie to the board here looking for help.
I'm getting a code 24. My Haynes manual says thats a Vehicle speed sensor but not much more. I only get this code when I'm putting around mountain roads in 4 wheel drive. The truck doesnt seem to be running any different when the code comes up. Where is the VSS? Could someone shine some light on what could be causing this code?

Thanks,
Tim

Oh yea, the truck is a 87 GMC 3/4 ton 4X4. 350/TBI, Manual tranny
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Old 11-22-2003, 01:01 PM   #2
Prerunner1982
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maybe a bad sensor... i dont know. unfortunately 95% of everyone here owns a pre-87 truck... you might consider posting in the 88+ board... just and idea... the gurus here might know....
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Old 11-22-2003, 01:38 PM   #3
mike reeh
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the VSS on your truck will be near the output shaft on the transfer case, where the speedo cable would normally hook up..

I dont know what year they started going to a complete electronic (cable-less) speedo system but thats how my 91 burb is. When you turn the key "ON" does the speedo goto 0 mph? (indicating an electronic guage)

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Old 11-22-2003, 02:48 PM   #4
toytruck
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From the book. VSS Vehicle Speed Sennsor. This sensor sends a frequency signal to the ECM. The frequency increases as the vehicle moves faster to give the ECM vehicle speed information. My 88 k20 sub with 400 turbo doesn't have one of these. I would try resetting the computer. You can clear it buy unhooking the battery cable for a few mins. I have noticed that anytime that I change something on the motor(like putting on a spacer) I needed to reset the computer to keep from getting a code. Hope this helps. Good luck.
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Old 11-22-2003, 11:20 PM   #5
Jason Spears
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I have the '87 GM manual. You're going to need a scan tool to find out if you have a problem with your VSS. The test involves comparing the VSS output to the actual speed. Hopefully you know somebody with one. Good luck.

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Old 11-23-2003, 01:04 AM   #6
Jonboy
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there is a good chance it is the buffer that pugs in to the back of the speedo head. It reads the revoultions of the speedometer cable.
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Old 11-23-2003, 12:57 PM   #7
TB6587
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Thanks everyone! My truck does still have the speedo cable. In fact, for a while now my speedo has been acting up. Especially at low speed it bounces around alot. It seems to settle down and act fine after I'm up to speed and heading down the highway so I havnt been to worried aout it.....Ok I'll admit it. I've been to dang lazy to replace it. lol Anyhow, now I wonder if it isnt the source of the problem after learning of the buffer plug that jonboy mentioned.
Thanks again everyone!!! Happy Holidays to all!!!

Tim
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