speedometer/ speed sensor issue
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speedometer/ speed sensor issue
2002 f150 5.4 liter. Lost my transmission had it rebuilt, Now when you hit 60mph speedometer jumps from 60 to 100mph and governs out. Mechanic replaced speed sensor did not fix the problem. But as a kicker the truck only does it while actually driving. Had it on the hoist no issue get it on the road hit 60 speedometer jumps and governs out again. Could this possibly be an ecm issue from previously logged data, bad instrument cluster? He stated that there was no damaged wires in the harness. Any ideas would be appreciated
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Joined: Sep 2006
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You have an all electronic dash that gets its info from the PCM.
If the speedo goes up like that it is being driven by the PCM.
I would take a look at the speed reading during Hec diagnostic access to see if it follows the same action.
The dash can't normally trigger a governor function.
What this means is accessing the dash test and stepping to the 'enG' indicator that should show the mph reading in the digital display to see if it does the same.
The pattern suggest it is the speed sensor circuit.
The PCM gets its speed indication from the sensor then calculates the signal to send to the dash.
Based in the data stored in the vehicle ID block, in program;
if that data is corrupted or missing should set a code 1639.
Obviously if the speed calculation goes that high, the governor function is triggered as it was designed to do.
Not of much help but that's about how it works.
You might reference the OBDII document for 2002 page 45 for this info.
Good luck.
If the speedo goes up like that it is being driven by the PCM.
I would take a look at the speed reading during Hec diagnostic access to see if it follows the same action.
The dash can't normally trigger a governor function.
What this means is accessing the dash test and stepping to the 'enG' indicator that should show the mph reading in the digital display to see if it does the same.
The pattern suggest it is the speed sensor circuit.
The PCM gets its speed indication from the sensor then calculates the signal to send to the dash.
Based in the data stored in the vehicle ID block, in program;
if that data is corrupted or missing should set a code 1639.
Obviously if the speed calculation goes that high, the governor function is triggered as it was designed to do.
Not of much help but that's about how it works.
You might reference the OBDII document for 2002 page 45 for this info.
Good luck.
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