Originally Posted By ruderunner
Ecm needs vss readings for control of OD.

No vss=no OD


Diagnosing a problem is mostly a matter of elimination, comparing what other systems use the same inputs and are working correctly can eliminate that component or sensor.

VSS is used by the speedometer and cruise control. If the VSS was bad the speedometer would be inop or erratic as well. The PCM only needs to know that the vehicle travelling at least 32 MPH for it to allow O/D. It could be reading 40 to 60 MPH regardless of actual speed and the O/D would still work.

Thus, everything else working fine leaves only the TPS.

"Follow me the wise man said, but he walked behind"


'92 D250 Club Cab CTD, 47RH conversion, pump tweaks, injectors, rear disc and hydroboost conversion.
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