Speedometer bouncing

Tiny
56FOURDR
  • MEMBER
  • 2002 FORD F-150
2002 Ford F150 4.6l automatic, 46000miles.
My speedometer will go up and down, 15-100mph, by itself when I am idling at a light or below 10mph. When the speedometer max's at 100mph, the engine shuts off. Also, I noticed my odometer changes as if I am going the speed the speedometer shows.
I did a search on the forum and found a thread with the same poblem, where you said it was possibly a loosed ground. That doesnt sound right.
here is the original thread:
"Question: 2002 Ford F150 mileage: 140000. My truck started cutting out or stalling when in idle mode and/or when I go to release the clutch to take off. Whenever it did this the mph needle would also “wave around” as I am going down the road. If the truck took off OK and I noticed the speedometer needle would wave around, I would be forewarned about coming to a stop on an incline. This would last a day or two and then go away for 2-3 weeks and then come back to haunt me again. After 4 months of this along with going to four Ford dealers for an answer, this problem came back for good and nobody seems to know what’s going on. Finally, I went through the fuse list. Found the very last fuse that had speedometer on it, along with nothing else that pertained to my truck. Pulled this fuse, wiped out my electronic odometer along with my speedometer needle. Now my truck runs fine. Is it the speedometer sensor? That’s the only logical answer that I have heard. I’ve been there done that with spending money to replace this and that to have my vehicle not get fixed. I am looking forward to your opinion. Thanks for your time.

Answer: We do not think the problem is the speedometer sensor. Check for bad or loose ground connection to the instrument cluster."
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Wednesday, February 21st, 2007 AT 2:46 PM

33 Replies

Tiny
NOS
  • MEMBER
I'll try this one. Have you checked the sensor at the back wheels. It is located in the middle of the differential houseing on top. Also ckeck the wiring coming from that switch trase it up a ways I have seen them get rubbed by other cables and hoses and break the wire inside. This sensor controls the ABS, speedo and cruse. If speedo is jumping aroun chances are the wire is looseing contack and regaing and that makes it jump also the cruse gets it's signial from the VSS. Check these wires out close 8) NOS
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Thursday, February 22nd, 2007 AT 1:33 PM
Tiny
DRJONEZ
  • MEMBER
  • FORD F-150
Hello. I own a '97 F-150 with 165000 km. It has a 4.6L V8, 4x4. My question is this:
A couple days ago, my speedometer started, for a lack of a better term, bouncing about 10 kph. So basically, when the gas is applied, or under load, the speedometer will read 100kph. When I take my foot off the gas, the speedometer will increase to read 110 kph before the deceleration of the truck is read, then back up about 10kph when I apply the gas again. It only started doing this over the last couple of days. I also noticed that if I put the truck into 4x4 mode, the speedometer reads true, with no fluctuation between a loaded and unloaded scenario.
Another thing, the OD light starts flashing after driving for a short time. This condition has been going on for a long time, and was told not to worry about it as long as the transmission will go in and out of OD, which it did, and still does.

Thank you. Donation is coming, but in a hotel away from home and have no secure connection, really.
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Wednesday, October 30th, 2019 AT 5:33 PM (Merged)
Tiny
JACK42
  • EXPERT
Have the PCM scanned, it should have stored a code that will most likely lead to the fix for both the flashing light and the bouncing speedo. Then I would start with the Vehicle Speed Sensor
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Wednesday, October 30th, 2019 AT 5:33 PM (Merged)
Tiny
DRJONEZ
  • MEMBER
OK. Exactly where would I find that and what will I need to replace it ie will I be able to do this myself
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Wednesday, October 30th, 2019 AT 5:33 PM (Merged)
Tiny
JACK42
  • EXPERT
Yes you can do it. It is located on the left rear of the trans, or on the tailshaft of the transfer case. I would recommend a factory Ford part
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Wednesday, October 30th, 2019 AT 5:33 PM (Merged)
Tiny
DRJONEZ
  • MEMBER
Hi there. I went to NAPA and bought a new speed sensor, had it installed and. Blah. Still doing the same thing. I now and officially getting worried. What would you recommend next (please don't say replace the transfer case) lol.

Do you have any recommendations at this time? Still looking forward to hearing back on this issue as I am now back home and have the ability and time to deal with this.

Thank you in advance.

That will be just my luck.

Look forward to reading your reply
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Wednesday, October 30th, 2019 AT 5:33 PM (Merged)
Tiny
TONHENRY
  • MEMBER
Hello, I have basically the same problem with my 97 F150 4X4 4.6 185000 miles. Only my speedometer doesn't work but sometime it goes up to as high as 45 mph for a second or two. AZ shows P0500, speed control sensor, for mine. I was told it is located on top of rear differential on these models. Please let me know what worked to fix yours. At the moment I can't afford to buy more sensors than I have to.
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Wednesday, October 30th, 2019 AT 5:33 PM (Merged)
Tiny
KEN
  • ADMIN
Hello,

Yes it does sounds like you have a speed sensor that is going out which is located and the rear of the transmission or transfer case. Here are some diagrams so show you where the sensor is (below) Please let us know if you need anything else to get the problem fixed.
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Wednesday, October 30th, 2019 AT 5:33 PM (Merged)
Tiny
RAY BOILEAU
  • MEMBER
Not enough information you left me hanging.
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Wednesday, October 30th, 2019 AT 5:33 PM (Merged)
Tiny
JROSE51956
  • MEMBER
  • 1995 FORD F-150
  • V8
  • 2WD
  • AUTOMATIC
  • 230,000 MILES
I have 95 ford pickup, and the speedometer is bouncing back and forth. I have changed the speed sensor on the rear end and changed the gear oil and gasket on the rear. But I still have the same problem. Any suggestions on what to look for now?
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Wednesday, October 30th, 2019 AT 5:33 PM (Merged)
Tiny
DAVE H
  • MEMBER
SPEEDOMETER
Turn ignition on. Go to next step.
Observe odometer. If odometer display is on and digits appear normal, go to next step. If odometer display is not on and/or digits do not appear normal, go to step 6).
Observe odometer. If word ERROR appears, replace speedometer. If word ERROR does not appear, go to next step.
Test-drive vehicle. If odometer accumulates mileage, go to step 9). If odometer does not accumulate mileage, go to next step.
Test-drive vehicle. If indicated speed on speedometer increases with increasing vehicle speed, replace speedometer. If indicated speed does not increase, go to step 8
Inspect fuses. If fuses are okay, go to next step. Replace fuses and repair shorted wires if necessary. If speedometer and odometer still do not operate, go to next step.
Turn ignition on. Backprobe terminals No. 1 and No. 3 of Programmable Speedometer/Odometer Module (PSOM) harness connector, located behind instrument cluster. If battery voltage does not exist, repair appropriate wire from fuse panel. With ignition off, measure resistance between terminal No. 2 and ground. If resistance is greater than one ohm, repair appropriate wire.
Set DVOM to measure AC voltage. Backprobe PSOM terminals No. 4 and 5. Test-drive vehicle. If voltage increases smoothly from zero to approximately 3.5 volts as vehicle accelerates to 30 MPH, replace speedometer. If voltage does not increase as specified, repair speed sensor circuit.
Test-drive vehicle. If indicated speed on speedometer increases with increasing vehicle speed, speedometer is okay. If operation is not as specified, replace speedometer.
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Wednesday, October 30th, 2019 AT 5:33 PM (Merged)
Tiny
KEN
  • ADMIN
Did you look at the diagrams in the post to show the location of the sensor? What did you need help with?
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Wednesday, October 30th, 2019 AT 5:33 PM (Merged)
Tiny
TOPLAIT
  • MEMBER
Also could be the "Exciter Tone Ring." Located inside the rear end. That is what happened to my 1992 F-150.
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Wednesday, October 30th, 2019 AT 5:33 PM (Merged)
Tiny
LADDJAG1
  • MEMBER
  • 1995 FORD F-150
1995 Ford F150 V8 Two Wheel Drive Automatic 121k miles

Hi, My speedometer needle starts bouncing at 32mph. Smooth as glass up to there. Worked fine till sensor on transaxle quit. Replaced rearend sensor and just bounces now above 32mph. Was told there is a plastic gear that is worn in the tranny? Any truth to that or is it the cluster? Thanks in advance, Joe
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Wednesday, October 30th, 2019 AT 5:33 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
Did you replace the VSS (vehicle speed sensor)?
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Wednesday, October 30th, 2019 AT 5:33 PM (Merged)
Tiny
LADDJAG1
  • MEMBER
Hi, The mechanic replaced the sensor on the top of the rear end diferential. That got the speedo working up till it hits 32 then bounces. I found last night a wired plug about 11 o'clock from the prndl swicth thats held in by a 8mm bolt and removed it. There was no gear on it, just a black plastic plug with what looks like a metal (magnetic) sensor on it. I put it back in. I pulled the cluster to make sure it was connected good and it was. Thats all that been done. Thanks in advance, Joe
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Wednesday, October 30th, 2019 AT 5:33 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
Was the mag clean?
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Wednesday, October 30th, 2019 AT 5:33 PM (Merged)
Tiny
ICEMANSADIE
  • MEMBER
  • 1995 FORD F-150
  • 4.9L
  • 6 CYL
  • 2WD
  • MANUAL
  • 267,000 MILES
Speedometer jumps most of the time sometimes it does not move. When problem started the needle on the speedometer would jump when I hit a bump in the road. I replaced the instrument cluster and the speed/abs sensor to no avail.
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Wednesday, October 30th, 2019 AT 5:33 PM (Merged)
Tiny
HMAC300
  • EXPERT
Check for a bad speed sensor in transmission or a shorted wire going to speedometer.
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Wednesday, October 30th, 2019 AT 5:33 PM (Merged)
Tiny
STEVE W.
  • EXPERT
Sounds like a short in the speed sensor wiring or a bad connection. If you have access to a good scan tool that can read live data you could connect it, select the speed sensor feed and then start wiggling and tugging on the wires and watch for the signal to drop out.
The other option would be to trace out the wires, disconnect them on both ends and then trace them with a meter.
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Wednesday, October 30th, 2019 AT 5:33 PM (Merged)

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