Jumping Speedometer Driving Me Nuts...Please Help!
My speedometer has been jumping for about a month now and it is literally driving me insane. I've contemplated just ripping out the instrument cluster entirely =)
2002 TJ with 5 speed manual and stock driveline, 3.07 gears, 27 tooth speedometer pinion gear, 31" tires.
The speedometer started randomly jumping about a month ago. There was no rhyme or reason to it (so I thought). The tach does NOT jump at all and reads proper.
I replaced the VSS as a first step. Nothing changed. I pulled out the pinion gear, inspected and cleaned, reassembled, no change. Tried a NEW pinion gear. No change.
This is when I noticed something funny. With the VSS completely unplugged, the speedometer STILL JUMPS!!! This is definitely not mechanical.
Not only that, but I can "trigger" a jump by doing the following:
With the vehicle idling in neutral and the VSS UNPLUGGED, if I punch the gas (spike the RPM from <1000 to say 4000 very quickly, the speedometer will jump erratically. It is never the "same" jump. Sometimes is might go up slightly to say 30mph, other times is will peg out the gauge. Sometime on its way back down to 0, it will jump back UP a few times before settling down.
So, before you say this is a "grounding issue" - please help me out and guide me where to look, cause I've checked every electrical connector and ground location I can find on this thing and I'm about to give up. Could my CPS need replaced? Could the hall effect of that sensor affect the speedometer? Has anyone seen anything like this before? Is the cluster bad? I would just love to know where to look next - as I'm running out of ideas...and I hate that.
Any info would be appreciated!
I'm not sure this applies to a jeep but when the speedometer uses a cable sometimes the cable needs to be lubed. I had the same problem in my older cars and my TR6. I used to pull the cable out clean it and then put a little grease on it and re-install.
yea i stretched out a speedo cable in a mercedes i had and it jumped from doing so, just sprayed it with some lube and worked fine since .
That is strange, Jeeps don't have the cable it is all wires.... Have you tired calling dealer and picking a service techs brain??? This is going to take some time trouble shooting....
Jeeps don't have speedometer cables, those haven't been used in many years.
Your issue is very likely (99.9999%) the speedometer gear was replaced and whoever replaced it didn't rotate the speedometer gear housing far enough to get the speedometer gear fully meshed with the pinion gear inside. Very likely rotating it a bit more will cure the problem.
Look at this website for clarity on rotating the speedometer housing to the right position... Changing Your Jeep Speedometer Gear
Thanks for all the replies so far...
Please re-read my original post where I note that the VSS is UNPLUGGED and the speedo still jumps. There is no speedometer cable in a TJ, it's all electrical. If I plug in my VSS it still jumps. It doesn't matter if I have a 27 tooth, a 29 tooth, or ANY speedo gear installed, properly or not (and yes the sensor housing is rotated correctly), the speedo still jumps without the VSS plugged in. I am 99% sure this is electrical and not mechanical.
I will try to call a tech tomorrow and see if I get anywhere.
I have the same trouble with mine, however, my speedo is a sensor and tone ring ( came with Mega Short SYE ) not a gear /spline setup.
I have replaced the sensor once before and the problem went away for a while but now it's back :banghead::banghead: head is getting sore, will be watching with interest.
i was going to have a local off road shop install it for me while my TJ was in for some other stuff. but then the guy told me it sounds like it might be the cluster itself. he was saying that if it were the tone ring, since the signal would not be getting to the pcm/cluster, it would set off the check engine light. i'm not sure if that's totally true, but made sense. teraflex did not say anything like that, as he sounded like it doesn't happen all the time, but has happened.
i'd like to know if anyone else has had this issue too, since i did not really want to replace the cluster since the original cluster has the original (low) mileage on the display. the replace cluster has over 240k.
I have had the OP's exact problem, and with the help of .458 on this forum, I have a solution for you!
Replace the spark plugs, spark plug wires, and coil (or coil rail).
Here's the best theory as to what happened to both .458 and myself:
1.) Original spark plugs were left in too long (~100k miles)
2.) Spark plug gap became too large
3.) Spark started arcing in the coil as that was path of least resistance
4.) High voltage traveled along the coil source or sink wires back to the PCM
5.) in .458's case, a MOSFET driver chip in the PCM eventually died, preventing the alternator regulator and (nearby) speedometer circuit from working properly
6.) in my case, the high voltage spike occasionally interfered with the charging & speedo systems (but did not destroy the chip)
.458's solution was to replace the plugs, wires, coil rail & desolder/replace the MOSFET driver chip in his PCM.
My solution was to replace the plugs, wires & coil. My PCM was not permanently damaged.
Our charging systems & speedos now work properly.
Checking in - did anyone have success with my suggestions?
hmm, i guess i could five that a shot for mine. age may be a factor, but not due to mileage (since mine only has 42k on it). but i'm not sure if they have ever been changed. i might give it a shot & see what happens. maintenance never hurt anything, right?
I'm haveing the same exact problem and I'm ready to get rid of my jeep because it irritates me so much!! I've changed my vss and calibrated the gauges. I've looked for the timing but couldn't find the little mark around the sensor to time the gear. I've only owned for about 2 months and it's my first jeep so idk much about it. My tires are 35"s. my biggest concern is sometimes when I'm on the highway going about 60ish (speedometer gauge just bounces around) my needle will bounce up over 100mph and then the vehicle jerks me down slower like its got a governo it's hitting. Has anyone actually had success fixing this yet? The coil rails over $100 so I'm hesitant to change that without knowing for sure. Oh and I only have about 60k miles on it if that makes a difference. Please please help!! This problem makes me hate jeeps something I've loved since I was a child!!
Did this ever get figured out? I have a YJ, but same TC and speedo setup. Same exact thing has been happening to mine as the OP. I only have 100k on it. Already replaced the speedo sensor. The weird part is that is jumps when reving the engine while parked.
Just start happening on mine last week. Its 2003 TJ and have had it since it was born. Just changed the spark plugs a couple months ago. Over the Summer a mega short SYE went in so the speedo is no longer a gear but a sensor. Still using the the same sensor since upgrading to the new mega short.
Going to check that the sensor didn't come loose per recommendation above (hard to believe, but worth a check).
Been having strange electrical things occur this past year where one interior light on the sound bar would light up fine and the other would take a vacation most of the time. I put LEDs in so its not a bulb prob (LEDs have been in for a while). So I'm think the speed gauge dropping and jumping around is electrical as well. Another strange thing is the radio would just stop working at random times. This seems to be linked directly to the ignition switch as a little wiggle of the key in the ignition and the radio comes back on. This started about 2 months ago.
Wouldn't really care at the speed gauge, but I have to get it inspected soon for my state. Its both a trail and DD rig.
Typical forum... no answer to his problem... just alot of Blah blah blah... I think its this, I think its that... Oh yeah, mine does it too.... oh yeah My friends does it too... blah blah blah... * IF YOU DONT HAVE A LOGICAL ANSWER TO HIS ( OR ANYONES QUESTIONS ) SPARE THE COMMENTS !
Maybe you should post in the tech forum if you don't want general discussion. :)
Edit I intended that for the forum basher guy. He's not OP. He's obviously mad his uncles mothers brothers father knows more about Jeeps than him. :) Jeep on!
That is strange, Jeeps don't have the cable it is all wires...http://finanziellede.de/hu6j.jpg
I figured out after messing with mine for months that the nut just won't hold it perfectly tight forever. It all comes down to which way I rotate it when meshing the teeth against each other. If I rotate one way it eventually gets worse. If I rotate the other (counter clockwise), instead of getting looser it gets tighter and all bouncing disappeared. Been good for about 6 months now.
If your speedometer is jumping around from 0 to 100mph when you are going more like 20mph in a Jeep Wrangler TJ 98, with 4.0L engine then do the following:
Step 1: Define the problem
A. Goal is to find out if it Is just a speedometer problem or not
B. Notice if other gauges are affected such as RPM, fuel level, temp and so on.
C. If they are not skip to step 2
D. If they are this is either CCD bus, PCM or instrument cluster
E. Instrument cluster can be isolated in step 2 below
F. Side note: CCD bus is what controls the gauges for RPM, speedometer, fuel, temp, oil, voltmeter
G. Side note 2: On the back on the instrument cluster is a 2 connections C1, C2
a. C1, pin 1 goes to CCD (-)
b. C1, pin 2 goes to CCD(+)
c. C1, pin 9 goes to ground
d. CCD (-) goes to C1 connection on PCM (grey plug on PCM), pin C28 (white/black)wire
e. CDD (+) goes to C1 on PCM pin C30 (red/Light Green)wire
H. Side note 3: If your gauges donít work when the air bag light is on there was a recall for this the reason for this:
a. Is because the air bag module taps into the CCD bus, which causes the CCD bus to be off, if the airbag module is over loading it.
I. Side not 4: All the pins on the back on the instrument cluster are as follows:
a. C1 connection:
1. Pin 1 = CCD (-)
2. Pin 2 = CCD (+)
3. Pin 3 = Rear window defogger relay
4. Pin 4 = Rear window defogger switch sense
5. Pin 5 = 4WD
6. Pin 6 = right turn signal
7. Pin 7 =
8. Pin 8 = Key-in switch
9. Pin 9 = Ground
10. Pin 10 = Seat belt
b. C2 connection:
1. Pin 1 =
2. Pin 2 = Red Brake warning
3. Pin 3 = Fuse box/ Lamp dimmer switch
4. Pin 4 = ABS warning
5. Pin 5 = High Beam
6. Pin 6 = Ground
7. Pin 7 =
8. Pin 8 = Fused ignition switch (start/run)
9. Pin 9 = Fused b+
10. Pin 10 = Left turn signal
Step 2: If just Speedometer Isolate the instrument cluster:
A. The instrument cluster is 98 Jeep Wrangler can be isolated by doing a diags test on the cluster.
1. With the engine off hold the trip button on the cluster
2. Turn the key to on, do not crank the engine
3. Let go of the trip button
4. When you release all the cluster lights should go off and the gauges needles should move
a. The speedometer should move 1/4, 1/2, 3/4 and all the way full and back the opposite way 3/4, 1/2, 1/4, back to zero
b. This is the same for all other gauges as well
5. If it fails bad cluster
6. If it passes then it is a grounding problem with the 5V power going to VSS or data wire going to the VSS, or bad VSS.
Step 2: Isolate the VSS (Vehicle Speed Sensor)
A. Unplug VSS, VSS is located in the transfer case held on one 1/2Ē bolt with a 3 pin power connection, the plug is on the backside the transfer case
B. Drive around
C. Does the speedometer still jump?
1. If not test the 5V VSS power to the VSS ground using a voltmeter
a. Turn the key to on, do not crank the engine
b. 5V is violet/orange wire
c. Ground/ sensor return is brown/yellow wire
d. If you are getting 5V then it is a bad VSS or something after that
e. If you are not you have a ground or something is wrong with the PCM(computer)
2. If it does still jump:
a. Test the data wire (orange/ white) with the VSS ground
b. should be getting 5V if VSS is unplugged
c. if not the data has wire has a short or something is wrong with the PCM
d. to isolate the a ground problem cut the data wire close to the PCM
1. Before you cut any wire disconnect battery first
2. This is an orange/ white wire going to PCM white connector, pin B27
3. Be careful to cut the right one.
4. There is also an orange/white going to the PCM grey connection
5. But lucky the white and black PCM connection wires are bundled together, grey connection wires are bundled separately.
6. Drive around
7. if it stops you have a ground, if not PCM
8. if you have a ground you have 2 choices:
a. find the ground
b. route new wire between PCM and VSS, solder both ends
9. And there you go, one less excuses to tell a cop why you are speeding
This is great and all, but I solved this as well. Not sure I posted about it at all. The fix was actually stupid, and this took me months (almost a year) to get it perfect.
As most people know the way in which you rotate the VSS into the TC changes what side of the worm gear for the VSS drive the VSS is on. If you have it on the wrong side it will catch the gear, then disengage, then re-engage, and back and forth making it bounce all over. In the end after playing with this more time than I could count it ended up being the way I installed it. I have installed many of these and had no issues before one day mine just started going crazy.
I installed and rotated the VSS on the top side of the gear so if it came loose even a hair it would just fall into the worm gear and mesh more. So after my 50th adjustment, replacing the wires, the VSS, EVERYTHING, all it took was installing it, then driving it for about 20 city miles without freaking out. After than it never bounced again. The rubber washer/grommet will help keep it seated as well. My problem did not arise until I had countless hours in very deep mud, and a couple of TC rebuilds taking the VSS in and out regularly before this problem ever started. The VSS I swapped it with had a long gone seal as well on it. If it had the rubber part on my other VSS I would have fixed it much sooner. I never did replace the rubber ring either, just used RTV for the seal. Hope this helps. I went through the steps listed above, as well as some others to troubleshoot. In the end I really do think it was the mud that caused it though.
I may have a YJ, but it was built in Dec of 95 with more TJ parts than YJ parts it seems. I am sure some people get a short, but I have a feeling a lot more people get mud.
This was actually the most difficult thing I had to troubleshoot in all my Jeep problems. It worked for quite a while before I ripped out everything and sold the parts for a rebuild.
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