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[SewperDrewper]

So onto another issue. Along with the bad head gasket, my speedo has never worked right which is throwing my truck into "limp mode". I pulled and replaced the speedo sensor, and that didn't change a thing. What else could be causing the problem. Keep in mind that the speedo used to work erratically, and now it almost never works. Thanks.

 

[icanfixall]

Without knowing what year truck you have its impossible to speculate on whats wrong. I'm only guessing here but do you have an E4OD trans.... A tach not working properly will cause a limp home mode too. So wil corrosion on the electrical connecters to the trans.

 

[rhkcommander]

Without knowing what year truck you have its impossible to speculate on whats wrong. I'm only guessing here but do you have an E4OD trans.... A tach not working properly will cause a limp home mode too. So wil corrosion on the electrical connecters to the trans.

was about to say this too. speedo should be mechanical... easiest way I can imagine to see whats up is to see if the cable is spinning by pulling the cluster, or crawling under to where it hooks up. if its not the cable idk what it would be but speedo shouldnt affect the autos, c6 should be fine and e4od needs tach

 

[SewperDrewper]

It's a '91 7.3 with the E4OD...sorry for the lack of info. I pulled the speedo cable that runs into the speedo sensor and turned it over and it spun the speedo just fine. That's what's kinda throwing me for a loop. The tachometer works just fine, to the gauge anyway.