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  1. #1
    Medium Load Member Elroythekid's Avatar
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    2007 Pete 387 speedo/cruise issue

    Why do I get the weird ones?? My speedo does not register anything until almost 75 kms hr, it then will start to slowly catch up until it reaches the actual speed of the truck at about 85 kms hr. Ok so speed sensor right?problem is the cruise works when you are above 50 kms (measured on gps) but below 75 when speedo is reading 0 kms hr, and it works when at hwy speeds above 85 when speedo is reading correctly. Ok so not speed sensor?? BUT the cruise quits when you are between 75-85 kms hr and the speedo is slowly working it's way from zero to actual speed. Mechanics at Pete haven't got a clue checked connections they are fine speedo head is $650 they won't let me try it first and no returns on electrical so that's out. And passing them my checkbook while they spend $99 hr trying to figure it out ain't happenin! Anybody else see this before or have an idea?

  2. #2
    Road Train Member Heavyd's Avatar
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    Everything is feed to the engine ECM. The ECM is reading vehicle speed and controlling your cruise control. ECM should be feeding the speedo back the vehicle speed. Are the techs able to see what road speed the ECM is seeing while driving? Has the speedo sensor been cleaned or adjusted or measure for proper resistance? Any rubbed wires for the sensor? I am not 100% sure on Petes, but I think the cab has its own computer that may be sending faulty info to the engine and also to the speedo gauge. Sounds like and very neat problem. I am sorry you're experiencing it, but I would love to dig into it!

  3. #3
    Medium Load Member Elroythekid's Avatar
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    They just wanted to replace parts and see what happens? The tech said the sensor has to be working or the cruise would not set when the speedo is at the zero mark at 60 kms hr, but its weird it wont set when the speedo starts working its way up to the real speed, then starts working again when it reaches the actual speed?? He was stumped. Replace sensor first, then speedo, then? I have no idea what to do. Im going to stop in moncton and have them put the computer on and go for a drive and see if it registers at slow speeds, after that? Can you measure at the back of the speedo for signal? or do i just buy a speedo to eliminate that, would suck to buy a $600 speedo to find out its a wire?
    Are you a tech? where in Ontario are you? I just left Toronto, headed back East again.

  4. #4
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    My 08-389 would do some strange things at times. Speedo,cruise and dash lights. Someone suggested having my dash ESA software updated. $45 to Pete and problem never returned.

  5. #5
    Medium Load Member Elroythekid's Avatar
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    Looks like one bad connection and one bad speed sensor.. Hopefully everything will work!!

  6. #6
    Road Train Member Heavyd's Avatar
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    Sorry, I work at an International dealer, with your problem I highly recommend going to a Peterbilt dealer because this is a Peterbilt specific problem. I think there is something goofy between the body controller and the engine. The signal going to the speedo will probably be a digital one from the body controller, the body controller gets the original signal from engine. The cruise switch inputs will go to the body controller and sent digitally to the engine. You need a laptop to see all that. I don't have the Peterbilt software to check out the body controller. Keep us posted!

  7. #7
    Medium Load Member Elroythekid's Avatar
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    Turned out it was the speed sensor and the reason the cruise would set when the speedo was at zero is the switch on the maxi valve was not working du to a bad connection so it thought the truck was stopped brakes on and it was turning up the idle. Slightly confusing but now fixed!

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  9. #8
    Road Train Member Heavyd's Avatar
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    Trucks are cool!

    If something like this came in to us, the first thing we would do is get the laptop hooked up and go for a road test. ECM would be seeing a bad speed signal. Now you go straight to the sensor, quick and easy really. Too bad you had to mess around a bit. Glad you got it fix!
    Last edited by Heavyd; 05.04.2012 at 08.47 PM. Reason:: spelling

  10. #9
    Medium Load Member Elroythekid's Avatar
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    Ya the confusing part was why the cruise still worked when the speedo was at zero, made us think it was the speedo head.. oh well, fixed now!!

  11. #10
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    One thing that will happen too is the nut that holds the yoke tight will back off slightly. Just had this happen to my 387. Was about to throw that out there, but the cruise kicking on at low speed wasn't jiving. Basicaly, when the yoke gets a little loose the toner[where the VSS gets it's signal] is able to move up and down just enuff that the VSS loses signal. If it can't get a signal the ECM kicks the cruise off.