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1993 F250 4x4 IDI NA. All stock with stock tire size. E4od. 180k.
I'm getting the blinking light on shift column. I pulled the codes and comes up Code 29- Speed sensor. Happens when I am slowly backing into my uphill driveway or slowly pulling forward into it. I have cleared the code and it always returns under same conditions.The transmission shifts fine, but every once in a while it shifts hard getting up to speed when entering the freeway. No blinking light under normal driving. Speedometer needle is steady and seems accurate. Cruise control works. Transmission was rebuilt about 4 years ago, and have approx 20k on rebuild.
I replaced the VSS (on rear diff) with one from O'reilly's. That did not fix the problem. Still get code 29 and blinking light when backing into driveway. This new sensor also made the speedometer needle erratic at freeway speeds which wasn't a problem with the original. I took it out and returned it.
Next, I plan on a new Ford VSS from the dealer.
Any info or things I can try before I buy another sensor? Any info is appreciated.
Awesome! Thank you for the diagram w/ notes. That really helps!
So, after taking the instrument cluster off, I should be checking for loose connections? Or do I need a different PSOM Module? I see that I should check the ground on Pin 14. I did have the instrument cluster out a few times last summer sorting out a few issues, maybe I jarred something loose?
ok this is the connector on the PSOM that would be of interest.....
you should have continuity from pin 7 on the above connector to Pin 3 on the PCM.
between pin 3 and ground on the PCM you will have a Digital Signal... Square Wave to be specific when the vehicle is moving (jack up rear end) IF that signal is missing it is either wiring between the PSOM and the PCM or the PSOM or the PCM has failed components....
on the PSOM I have found bad components marked on this Image...............
OK let me point out this... you say the cruise control is working just fine .. that tells me that the PSOM must be fine...
you could try unplugging the Speed control Servo mounted on the Driver's side fender.... the idea here is to see if the Servo is loading the signal down too much.
no speed signal to the PCM is never helpful to the transmission and will shorten it's life.
EDIT: I would be sure to Chase that ground on pin 6 of the PCM as noted on my Image that I posted.
NOW IF it starts working fine with the cruise servo disconnected ...then that would tell me the signal is being loaded down and if it starts causing issues again when you plug the Cruise control back in then I would have to think that you have bad Capacitors on the PSOM PCB. as indicated on the PSOM Image that I posted.
