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Discussion Starter #1
About a week ago my truck would jerk when I would try to set the cruise control now when I set my cruise it does nothing and also, my speedometer is nice and smooth up to 60 mph and then it starts to sweep back and forth from 60-70 non-stop. I went ahead and and serviced my rear diff. so that I could inspect my tone ring and it is good also, tried 3 different speed sensors and I replaced the connector for the speed sensor. I would appreciate any feed back on what else, to check. Thank you!
 

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I know that on mine when I replaced the VSS I didn't get it seated completely. I ended up using a mallet to tap it down solid and it solved my problems.

I know that you have been through this before but have you checked the wiring from the VSS up to the dash?
 

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Discussion Starter #3
Thanks, bugman for the response I will double check the speed sensor. What would the proper way be to check the wiring. Thanks
 

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Here is a post that has how to check it. If you don't have a break out box, which most of us don't here is a link to the pin positions on the PCM connector.

 

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Discussion Starter #5
Thank you! Sir
 

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The caption of this pic explains how the PSOM works & what commonly goes wrong with it, and it contains links to more info:

(phone app link)


This one describes the GASSER cruise system (with external servo), but the circuits are nearly the same for these diesels:

(phone app link)
 

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Discussion Starter #7
Thank you! Steve83
 

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Discussion Starter #8
Update still having an issue with the speedometer once it hits 60mph it starts jumping/sweeping from 60-75 and down to 50 back up to 75 whatever is causing this i'm sure that's also, messing with my cruise control. I have checked the tone ring/exciter ring for any kind of damage and it is all good no nicks/chips I have put in two other VSS sensors also, replaced the pigtail connector I also, removed all grounds in the engine bay cleaned all connectors and the surface to where they bolt. I took it to our local diesel shop the only one that I trust here and they checked to make sure that the signals were getting through and everything that they could check was all good. They gave me their best educated guess as they are not 100% sure they thought it was a problem with the instrument cluster so, I bought another cluster and it is doing the exact same thing at the same speed as the other one. I sent out my other cluster to be checked out and I got a phone call yesterday from them and they told me that it all checked out good. At least now I have a spare Instrument cluster. Lol My next question is there anyway possible that the ECM could be causing the issue with my speedo I do have 2 known good ECM's that I could try but, I don't like swapping computers just for the hell of it just another chance to damage a pin. I'm not sure what all the ECM controls but, i'm willing to swap it out if it could effect the speedo. Maybe i'm just grasping at straws but, i'm running out of things to check and change out. Are there any ground straps that are attached to the dash? Any and all ideas would be appreciated. Sorry, for the long post but, this problem has me stumped.
 

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Sounds exactly what mine was doing after I put a new VSS in.

Come to find out the VSS was not completely seated into the hole. I used a mallet to seat it down and no problems since.
 

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I don't think the PCM outputs anything to the PSOM (it's the other way around). I'm thinking there was a good post somewhere regarding some weirdness with a PSOM and a resolution to it. Now to try and find it! Cheers!
 

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Discussion Starter #11
Sounds exactly what mine was doing after I put a new VSS in.

Come to find out the VSS was not completely seated into the hole. I used a mallet to seat it down and no problems since.
Thanks, Bugman I know that you mentioned that earlier in the post and I forgot to try that. I will do that tomorrow and post back with the result. I will feel like a dumba$$ if that's all it was but, at this point I wouldn't mind. Lol Thank you! for your response.
 

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Discussion Starter #12
I don't think the PCM outputs anything to the PSOM (it's the other way around). I'm thinking there was a good post somewhere regarding some weirdness with a PSOM and a resolution to it. Now to try and find it! Cheers!
Thank you! Patrick for the response. Yeah, I wasn't sure if the PCM would or not but at this point I was willing to give it a try. I have a gps to help keep track of my speed but, I'm so use to looking at my guages and it's driving me nuts watching the speedo needle jump around. Lol If you do find the post on the PSOM please, send me the link. Thanks
 

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Thanks, Bugman I know that you mentioned that earlier in the post and I forgot to try that. I will do that tomorrow and post back with the result. I will feel like a dumba$$ if that's all it was but, at this point I wouldn't mind. Lol Thank you! for your response.
That's exactly how I felt after all I went through when mine was giving me problems a couple of years ago. I pulled the cluster and sent it off only to still have the problem, just like yours. Everything was fine up to 60mph, cruse worked and no needle jumps but over 60 and the needle was doing the funky chicken and no cruse.

I don't even remember what I was going to do when I hit the top of the VSS with that mallet and I saw it move just a little. Then the second hit felt solid. I remember thinking that it can't be something this simple. I took it out of the garage and headed to the freeway for a test run. Everything was working as it was supposed to

Sent from my SM-J737V using Tapatalk
 
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Here are a couple of threads I found (but I don't think these are the one I was thinking of):

Cheers!
 

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Discussion Starter #15
Here are a couple of threads I found (but I don't think these are the one I was thinking of):

Cheers!
Thanks!Patrick I'll check them out when I have a little time to read through them.
 

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Discussion Starter #16
I want to Thank those that responded with replies. A big THANK YOU! to bugman for making me check the VSS again while it was raised up maybe 1/32" I thought surely that wouldn't cause it but, I'll be damned if it didn't. I don't mind being a dumba$$ for not checking it when you first mentioned it. Lol What I did notice when I pulled the sensor out I thoroughly cleaned the surface and fully seated the sensor in place when I went to tighten the bolt while shining a flashlight I could see that the sensor was raising up I pulled it back out and reapeated 3 times and each time when the bolt was snugged down it kept raising the sensor up and that was a brand new sensor. I went to napa and picked up a couple more and tried each of them and when fully snugged up they remained fully seated. Learn from my mistake even with a brand new sensor use a flashlight and watch closely at the sensor as you tighten the bolt that it is not raising up out of its seat not even the slightest bit.
 

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I believe that using the bolt to pull the sensor down was my problem.

While I didn't watch before I hit it with the mallet I could tell with the first hit that it was not seated completely and then when it did seat I could tell.

Glad you got it taken care of.
 

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Discussion Starter #18
Yeah, I rotated it and tapped it down before I put the bolt in and still watched it raise up off the seat. That new sensor went into the trash can I didn't want to take it back and have them resell it to someone else and cause them the same grief. Thank you! again bugman
 

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Sweet! I'm glad it turned out to be the VSS instead of the PSOM. Cheers!
 

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Discussion Starter #20
Yeah, me too luckily I only paid $125 for the instrument cluster so, at least now I have a spare. Lol Thank you! again for your input on this post.
 
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