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I have 2004 Wrangler Rubicon, 5-speed Manual with 4.0. On several different occasions I have had the speedometer register over 100mph before I could get to 3rd gear - prob going 20mph. All the other gauges in the cluster were operating fine. I bought the rig salvaged from front axle damage. the original cluster was swapped out as the seller said the odometer would not display. When I put the cluster in, I had this problem. I was told it was a cluster problem, so I bought one on-line, installed it and all was well for about 800 miles, then all gauges fine except the speedometer - which is way over reading the speed. Well, I bought another cluster and same problem. My mechanic said mostly likely the vehicle speed sensor, but none to be found for 3 to 5 days.
I am headed to the Moab Easter Jeep Safari tomorrow with Wrangler in tow. Will be picking up a speed sensor that a dealer in Denver has in stock.
What are the odds that this will correct my problem? I'd really like to drive my Jeep on the trails, after spending the better part of a year working out the bugs!
Thanks for any help!
 

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If you have it it was added on and could have been placed under the hood or inside the jeep best look at harness plug on speed sensor at rear of transfer case and see if there are splices or extra wires or a double plug and if there is trace where the extra wires go to find the tiny box
 

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The sensor has three wires a ground that to insure is common ground also runs back to PCM ground

A 5 volt power wire from PCM

A signal wire that runs back to PCM

If I was frustrated enough I would cut signal wire near PCM harness plug and run a new shielded wire to speed sensor signal wire grounding shield to sensor ground at sensor end and to PCM ground at PCM end but I might try swapping out sensor first
 

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Have you tried a pcm reset? This happens to my 2004 Ruby every time I disconect the battery. Do a search on a pcm reset. It may take 10 times to get it to take.
 

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Thanks for the info on the PCM reset, that did the trick for my rebuilt 2004 TJ. Previously it was acting like the original poster's--it would hit the 100mph governor at about 30 mph.

After the PCM reset it's about 12% off at 50 mph, definitely something I can live with.

The vehicle was originally a 1997, but completely rebuilt using a salvaged 2004 internals. Guess they forgot to reset the PCM. Glad it was a simple fix!
 

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I have the Yellow Box and it is plug and play. I did not splice or cut anything. I installed it, plugged it in and made several drives to set in the speed correction. That was a long time ago, no issues. Well spent money. And it does make the auto transmission behave much better. My speedometer responds crisply and is steady.
 
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