Intermittent speedo.

[David in NC]

The speedo on my son's '99 4.0 4wd XLT has become intermittent. It will just drop to zero all of a sudden. When it does this, the odo stops too, but the cruise keeps on working properly. The ABS seems okay. I've searched and read posts about speed sensors and plastic gears, but I'm still not sure what cures this problem. I guess the thing to do is to clean the sensor on the tranny tailpiece and check the ground. Any other suggestions? TIA.

 

[patrick112390]

The speedo on my son's '99 4.0 4wd XLT has become intermittent. It will just drop to zero all of a sudden. When it does this, the odo stops too, but the cruise keeps on working properly. The ABS seems okay. I've searched and read posts about speed sensors and plastic gears, but I'm still not sure what cures this problem. I guess the thing to do is to clean the sensor on the tranny tailpiece and check the ground. Any other suggestions? TIA.

i have the same problem too! it happens 3-10 minutes after start driving

i have already replaced the vss (vehicle speed sensor) in the t-case and that didnt fix it

i even caught it on video one time sometimes it will do this number before goin all the way to zero VVVVVVVVVVVVV

http://www.youtube.com/watch?v=nGzg6R_J5N0

 

[parad1mg]

i'm having the same problem plus the CC is acting up and dies along with the speedo.. what the heck is goin on?

 

[nssj2]

which sensor did you replace? 97s have 2 sensors. one on the transfer case and one on the rear diff.

 

[parad1mg]

i think t-case based on his post..

i havent replaced mine but only the CC and the speedo doesnt work.. no problems with the abs and no problems with shifting.. i do have a digital speedo hooked up to a vss wire that works perfectly..

 

[nssj2]

diagnostic steps for an inoperative/intermittent speedo

(instrument cluster power)
1) is the voltage of the white/yellow wire in the gem harness above 10v?

(open circuit from the speed sensor)
1) is the resistance of the gray/black wire above 5ohms?

(VSS)
1) remove VSS
2) is the resistance between the terminals between 300 and 200 ohms?
3) spin shaft on VSS. Does the voltage vary?

(drive gear)
1) visually inspect for damage or wear


edit::
if all these check out, it leaves a bad solder on the back of the gauges, or a bad servo for the needle.

 

[parad1mg]

Thanks for the info!

btw, should we check both vss 's from the t-case and rear diff?

 

[nssj2]

rear diff is the VSS, though some parts stores list them both as VSS. the one off the diff is for cruise control. no clue as to why they would have done this.

 

[Cobraguy]

You are discussing and diagnosing two entirely different systems. The OP is talking about a 99. That system utilizes the three ABS sensors for a VSS. As long as one is operating, there is a VSS signal. It comes from the ABS module and is distributed to where needed. If you have no ABS issues, and everything else requiring VSS is working, then you must have a problem with the speedo or the wiring to it...including the printed circuit.

 

[patrick112390]

i havent even touched the rear dif one... i may take it out and try cleaning it? this only happens after everything heats up.....i replaced the vss for a 97 thats on the side of the transfer case...while i was at it i replaced the gear thats on it to correct for my 33's so i know thats what reads the speed at least for my 97 because when it works.... i am spot on with the correct speed

if you havent seen my video thats exactly what it does ^^^^^^^^^^^^^

 

[nssj2]

cobra- there are 3 different people with slightly different problems here, im just listing the circuit for the SPEEDOMETER. there is only one wire which feeds to the speedo, gray/black on the gem harness. this is an intermittent problem, therefore hard to try and pinpoint. honestly could any sensor youve listed, none of which ive had fail on my 97, which is why i havent called out a specific component.

patrick- as cobra said, the systems are interdependent. if one sensor goes, you could possible have a fluctuating reading. your problem looks like a bad servo or the circuit grounding out, but if you read the voltage off that one wire, you will have an answer.

parad- yes check the resistance on them both. the couple times ive seen this problem on an f-150, it was the rear diff one. both sensors feed information about vehicle speed, pardon what i said last night, it was late lol. i would also recommend checking the voltage off said wire at the gem harness.

 

[patrick112390]

which wire and where is it located?

 

[ExplorerV6]

I had the same problem when I first bought the my 96, after a few few minutes of driving, my spedo would die. I found that if I gave it a good pound on top of the dash right above the instrument cluster, the guages would kick back in for a bit. I just replaced the whole cluster with one from a junkyard and it is working flawlessly now. Not sure what the cause of my problem was, but that was my solution and it has been working good for the past two years now.

 

[nssj2]

patrick, the is on the gem harness, which is located basically behind your cigarette lighter. pull the radio and the bezel and youre there.

explorerv6-that would be a bad servo or bad connection on the board of the gauges. glad to hear its workin

 

[patrick112390]

patrick, the is on the gem harness, which is located basically behind your cigarette lighter. pull the radio and the bezel and youre there.

explorerv6-that would be a bad servo or bad connection on the board of the gauges. glad to hear its workin

OH HAHAHA i was just ####iin around with radio connections a little while ago alright so i just check for voltage?

oh and btw i rather guessed it wasnt the cluster because i would give er a good wack on the dash and nothing-not even a needle quiver

 

[parad1mg]

cobra- there are 3 different people with slightly different problems here, im just listing the circuit for the SPEEDOMETER. there is only one wire which feeds to the speedo, gray/black on the gem harness. this is an intermittent problem, therefore hard to try and pinpoint. honestly could any sensor youve listed, none of which ive had fail on my 97, which is why i havent called out a specific component.

patrick- as cobra said, the systems are interdependent. if one sensor goes, you could possible have a fluctuating reading. your problem looks like a bad servo or the circuit grounding out, but if you read the voltage off that one wire, you will have an answer.

parad- yes check the resistance on them both. the couple times ive seen this problem on an f-150, it was the rear diff one. both sensors feed information about vehicle speed, pardon what i said last night, it was late lol. i would also recommend checking the voltage off said wire at the gem harness.

so it might be the one on the rear that's pretty much messed up that’s making my cruise control go crazy on me after a couple of minutes of driving?

GEM.. that small box that’s tucked all the way into the side huh? is that the same thing that controls the wipers? my wipers do go possessed from time to time..

 

[nssj2]

patrick-haha thats how it works. yeah pull the radio and look left, its a pretty decent sized connector. the gray/black is the one that feeds a voltage to the speedometer. check for a voltage parked, then if you feel like tapping into it, look for abnormal readings while driving. another option would be to find a really nice OBD2 reader to graph live voltages from sensors. now, if you don't find anything here, something is giving the abs module and gem a bad reading. i don't know how it reads the sensors, maybe someone else here does. Only way i know how find it is to graph the live sensor data

parad-worth a shot, like i said, im not familiar exactly how the abs module and gem process all the sensors. wipers going possessed is usually a bad relay or the notorious multifunction switch.

 

[Cobraguy]

cobra- there are 3 different people with slightly different problems here, im just listing the circuit for the SPEEDOMETER. there is only one wire which feeds to the speedo, gray/black on the gem harness. this is an intermittent problem, therefore hard to try and pinpoint. honestly could any sensor youve listed, none of which ive had fail on my 97, which is why i havent called out a specific component.

Wait a sec guys...are we talking the same year vehicle?? Please read his original post...he said it was a 1999. If that's the case, then that's not correct nssj2. There is no VSS signal from the GEM to the cluster. It comes directly from the ABS module. The GEM receives a VSS signal on a parallel circuit with the ABS...as does many other items. I'm discussing a 99...but if this is in fact a 97, then my description is wrong and the others are correct.

 

[nssj2]

oh dang, i saw the 97 on the left under his name and didn't even think twice about it. the other two here have 97s though. yes, disregard this information for the 99, as they use a different system.