Erratic Speedo Bus Bb Panel Open HELP PLEASE - JeepForum.com
 
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post #1 of 5 Old 06-27-2020, 10:42 AM Thread Starter
Markeje74
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2004 LJ Wrangler 
 
Join Date: Jun 2017
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Erratic Speedo Bus Bb Panel Open HELP PLEASE

Any help here would be really appreciated. I don't know what else to try. When I start out down the road I have no speedo until I let foot my off the gas, then the speedo starts to function..then becomes erratic right away.
This is what I have done so far in order.

1. I ran the dash test. All gauges light up and move as they should.
2. Tested VSS output and have 5v.
3. Pulled #38 gear in SYE. It was worn. Thought this would fix my issue. I then replaced with #39 gear as I am running 35-36" tires. Erratic speedo still exist. Made double sure it is clocked right for #39 gear.
4. Replaced VSS added new #39 gear. Same issue. No change.
5. Disconnected grounds from right side of motor and cleaned. Same issue. No change.
6. I looked into the SYE and the blue Ring gear looks good...but ONLY what I can see. I took a picture of it and it looks good. The VSS #39 gear seems to mesh well with it. It does slide on the yoke and stays in place.

So, what he heck should I try now? Does the magnetic sensor on the front of the transfer case ever cause this issue or something?

I really need some direction to go. I have not removed the bezel and cleaned the connections, but that doesn't seem to be the issue with the testing being good.


04 LJ-White-Auto-4.88/33" KM2's-5.5"Lift
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post #2 of 5 Old 06-27-2020, 11:08 AM
CJ7-Tim
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The cluster self test only tests the cluster internals, and nothing beyond that. Cleaning the cluster contacts is a simple and quick job.

Clean and snug dashboard ground G300/G302 .

Are there any current or stored Check Engine Light trouble codes ?



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post #3 of 5 Old 06-27-2020, 11:43 AM
Rubi4MyMrs
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That sounds like a wiring issue.

Getting on or off the throttle or even turning one way or the other causes the engine/trans/TC to shift & if there is harness damage or a bare spot in any of several wires it may cause any number of weird things to happen. Follow the speed sensor wires from sensor to firewall. If they pass along the firewall behind the engine be sure to carefully check there. The clearance is tight & that is an area known to have the harness rub against a bolt sticking through from the cab &/or an engine bolt & damage wires.
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post #4 of 5 Old 06-27-2020, 03:59 PM Thread Starter
Markeje74
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OK. I'll clean the cluster connections and check the ground as well.

Then I'll start the process of checking the wires from the VSS back to the front. They're all still in the original wire wrap. Not fun job for sure. But I did the voltage check and checked ground and they seem good. If I am checking them right. I found a write up on here or somewhere on the procedure, but my wire colors did not match was in the write up.

So does the magnetic sensor on the front of the transfer case have anything to do with this issue?

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post #5 of 5 Old 07-02-2020, 12:22 AM
mukluk
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Quote:
Originally Posted by Markeje74 View Post
OK. I'll clean the cluster connections and check the ground as well.

Then I'll start the process of checking the wires from the VSS back to the front. They're all still in the original wire wrap. Not fun job for sure. But I did the voltage check and checked ground and they seem good. If I am checking them right. I found a write up on here or somewhere on the procedure, but my wire colors did not match was in the write up.

So does the magnetic sensor on the front of the transfer case have anything to do with this issue?
What magnetic sensor are you talking about? The only "sensor" on the front of the xfer case is the range mode switch/sender.

I had a similar speedometer display issue last year, it ended up being caused by a dirty connection at the throttle position sensor. Cleaning and reseating the connector cleared the issue. Keep in mind the VSS has its own dedicated 5v supply, but it shares the same ground/sensor return as the MAP, TPS, IAC, CKS, CPS, ECT, TCM, o2 sensors, battery temp sensor, and clockspring. A short or voltage leak at any of those can cause a problem with the signals from the others.

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2005 LJ Rubicon
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