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PTO Problems


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New to the site and wanted to say hi before asking for help,

Im driving a 2015 Mack Granite RollOff with 41K on it and recently when I turn on the PTO it still always activates the hydraulic pumps but now is NOT disengaging the Idle shut down mode, is NOT activating the rev limiter and is NOT activating the governor to prevent the transmission from shifting past the first gear. If I had to guess i would say that the switch is not communicating with the Mack truck computer but is still communicating/working with the pumps themselves. Has anyone ever have this problem or heard of it and what can I do to fix it ? any help is appreciated and thank everybody in advance.

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As mackpro asked, what’s trans? If manual, possibly switch installed in air line to pto, if Allison , please correct me if I’m wrong, Mackp, then pto signal is controlled to vehicle ecu by trans ecu.  

And you thought only NASA had rocket scientist!!!!

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Shouldn’t have anything to do with the Allison ecm. If the pto light in the dash cluster  ( has to be the one in the cluster) is on , then the VECU should be getting the “ PTO on” signal and operate as per the Pto parameters that were programmed in the VECU ( Vechicle control unit) . Only  thing I can think of is , some sensor has failed or sending incorrect into to the VECU. Make sure the parking brake and stop light switches are working correctly. 

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  • 2 weeks later...

Hey just wanted to update on my situation and maybe this will help someone else, So I was able to solve the problem by getting lucky. It was actually the PTO switch itself, Even though the light turned on and turned on the hydraulics it’s not a regular rocker switch, it has a secondary part to it that’s attached from behind and looking from the front of it you would never know that until you take it out. Anyway the secondary part of it was loose and just had to be readjusted and tightened up.

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22 hours ago, Sanman said:

Hey just wanted to update on my situation and maybe this will help someone else, So I was able to solve the problem by getting lucky. It was actually the PTO switch itself, Even though the light turned on and turned on the hydraulics it’s not a regular rocker switch, it has a secondary part to it that’s attached from behind and looking from the front of it you would never know that until you take it out. Anyway the secondary part of it was loose and just had to be readjusted and tightened up.

Thanks for the fix! That'll help someone in a few years whos digging for answers!

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