Speedo is freaking out

EROCK

EROCK

TJ Enthusiast
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Dec 1, 2018
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188
Location
Arkansas
Went off roading in a heavy brush area today and now my speedo is flipping out. Also getting an intermittent Airbag light that may or may not be related. Speedo wire looks good coming out of the transfer case. Any ideas.

Video attached: notice the airbag light coming on at the end as well.

Gonna make another post but rev limiter has started kicking in a 3.8k to 4.1k. It will go threw 4k, kill power and then continue up to 5k before it kicks in again. This was also noticed the 1st time today. Usually dont get it above 4k. With the exceptions of getting on onramps occasionally.

 
I found some wires pulled out about 5 inches out of some loom tubing. I checked them for any damage and put them back in. No damage. Drove it to work this morning and all problems have ceased. I'm guessing that further down the loom, a wire may have some damage and putting it back in caused it to stop grounding out. Gonna give it a few more days to make sure no problems continue and I will put some extra loom and zip-tie it to frame real secure and high as possible. The loom does T off of the speedo gear wire loom.
 
Teeth look great on the speedo gear. It is simi-new. I changed it out about 5 years ago to match my 33s. Back to the drawing board. I have no idea what is causing it.

20240413_193855.jpg
 
macleanflood said:
Is it clocked correctly? You can rotate the assembly 90 degrees at time. Certain positions for amounts of teeth.

-Mac
Click to expand...

I forgot to clock it when I put it back in. Guess I'll do that in the morning. It's been 5 years since I messed with the speedo gear. Thanks for reminding me. E
 
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EROCK said:
I forgot to clock it when I put it back in. Guess I'll do that in the morning. It's been 5 years since I messed with the speedo gear. Thanks for reminding me. E
Click to expand...

Well I got lucky, it's clocked correctly. Any other ideas?
 
EROCK said:
Teeth look great on the speedo gear. It is simi-new. I changed it out about 5 years ago to match my 33s. Back to the drawing board. I have no idea what is causing it.
Click to expand...

What about the gear on the TC output shaft (in the hole), is it ok too?

I would suspect wiring, based on your first couple of posts. You might want to follow the VSS wires all the way up to the PCM. Maybe split each connector, see if there is any water or corrosion. Look for skinned or melted spots.
 
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So I've decided to replace the 3 wires from the VSS on the trans to the computer to eliminate any possible grounding issue. I spliced the 3 wires into the "circled area" in the picture on the corresponding wires. This must be the incorrect "spot" to splice because this caused the engine to not start once completed. Does anyone know where I "should" splice into the harness to eliminate the stock vss wires and a possible grounding issue?

20240425_111335.jpg
 
I have an erratic speedometer after an offroad trip though heavy vegetation. I found wires pulled from luming under the driver side rear quarte panel. I have checked VSS gear, replaced the VSS and reclocked. Checked a good portion of wiring. Checked the guages and their connections. So all I have left is rewiring the VSS to the ECU or replacing the TC worm gear. I've decided to the the wires first. Since that's more likely after finding wires pulled under the jeep.
So I've replace the 3 wires from the VSS on the trans to the computer to eliminate any possible grounding issue. I spliced the 3 wires into the "circled area" in the picture on the corresponding color coded wires. This must be the incorrect "spot" to splice because this caused the engine to not start once completed. Does anyone know where I "should" splice into the harness to eliminate the stock vss wires and a possible grounding issue?

20240425_111335.jpg
 
OP started another thread for this issue here.

@Chris - is there another way to handle a situation like this (OP abandoning a thread and starting another)? Just trying to maintain continuity for future readers...
 
sab said:
OP started another thread for this issue here.

@Chris - is there another way to handle a situation like this (OP abandoning a thread and starting another)? Just trying to maintain continuity for future readers...
Click to expand...

Thanks for letting me know. I merged them (y)
 
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That's as good a place to splice as any.

The speed sensor wire goes only from the sensor to the PCM. But the 5V and Gnd wires go from the PCM to the speed sensor and to other things (check the wiring diagrams in the 2000 service manual, page 8W-30-11). You might have bypassed something else which now has no power or ground.
 
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I was preparing a response, while OldBuzzard was responding, so this it duplicative, but maybe adds to the discussion...

OldBuzzard is spot-on (as usual). The following commentary assumes that you cut all three wires at the point shown by the red arrow in your picture, and then you ran new wires all the way to the VSS connector, which left a lot of stuff disconnected due to the splices in the harness. Here are the relevant manual pages, with the sensor ground wire highlighted yellow, the sensor 5V supply wire highlighted purple, and the sensor signal wire highlighted blue:

1714162654185.png


1714162709794.png


1714162732242.png


As shown above, there are four splices inside the harness that are no longer active after your splicing. They can be found in the splice locations section of the manual. Here are the relevant pages, with same-color highlighting:

1714163044019.png


1714163067805.png


The fix for your current predicament involves two steps. First, you need to reconnect the original wires at the splice in your picture above (red arrow). That will restore all functionality to the other sensors. That's the easy part. The second step is more difficult. To fix your original problem, you really need to find the break in the wire that's causing you trouble and reconnect it, assuming that it's a broken wire. Unfortunately, it takes patience, the ability to read wiring diagrams, and a multimeter to do that.
 
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sab said:
I was preparing a response, while OldBuzzard was responding, so this it duplicative, but maybe adds to the discussion...

OldBuzzard is spot-on (as usual). The following commentary assumes that you cut all three wires at the point shown by the red arrow in your picture, and then you ran new wires all the way to the VSS connector, which left a lot of stuff disconnected due to the splices in the harness. Here are the relevant manual pages, with the sensor ground wire highlighted yellow, the sensor 5V supply wire highlighted purple, and the sensor signal wire highlighted blue:

View attachment 522000

View attachment 522001

View attachment 522002

As shown above, there are four splices inside the harness that are no longer active after your splicing. They can be found in the splice locations section of the manual. Here are the relevant pages, with same-color highlighting:

View attachment 522003

View attachment 522004

The fix for your current predicament involves two steps. First, you need to reconnect the original wires at the splice in your picture above (red arrow). That will restore all functionality to the other sensors. That's the easy part. The second step is more difficult. To fix your original problem, you really need to find the break in the wire that's causing you trouble and reconnect it, assuming that it's a broken wire. Unfortunately, it takes patience, the ability to read wiring diagrams, and a multimeter to do that.
Click to expand...

This is awesome ^^^^^^ makes so much sense!!! Thank you. Also sorry about making a new thread. The old one was started 6 mths ago and didn't seem to get alot of responses any more. Thank you everyone for this great information. Hopefully this fixes the issue!! E
 
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OldBuzzard said:
That's as good a place to splice as any.

The speed sensor wire goes only from the sensor to the PCM. But the 5V and Gnd wires go from the PCM to the speed sensor and to other things (check the wiring diagrams in the 2000 service manual, page 8W-30-11). You might have bypassed something else which now has no power or ground.
Click to expand...

Thank you sir. This is perfect.
 
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Well rewiring the VSS started promising however after about 5 miles of working perfectly, it started doing it again. However this time it was very different. Before it would only do it while accelerating in 1st,2nd and sometimes 3rd. Now it does it just while cruising in 5th gear and for the 1st time, it did it while siting perfectly still with the engine at idle. Video is below.

 
If you have a code reader, you could display live data, and when it's acting up, look to see if vehicle speed from the PCM is screwed up, too. That would tell you if it was the instrument panel or not.
 
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