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Hi all ,new here. 

Just recently acquired a 1994 ford f150 xl 5.0L E40D transmission.

wasn't running when i got it but got it running same day. Needed new fuel and a little freeing up of the throttle body. Shortly after running check engine light came on, pulled ckdex a d received cod of 123. Truck seems to operate fine but doesn't kick down to passing gear when matted. Leave battery cable off for over 5 minutes start engine and seconds later check engine light is  back on. Does faulty TPS affect transmission kickdown?

Other slight problem heater function remains on defrost only cant get much from mix and nothing from floor, vent works fine. Have three knob controls one for fan speed, one for temp, and one for selection.

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HI, oldie62, welcome to the forums!  

The 123 code is TP (FIPL) throttle position, an indication that the TP circuit is above maximum voltage.  This is a voltage issue, either above or below, at the TP (FIPL).  The trouble will show up during vehicle On-Board Diagnostics or during normal vehicle operation as in your truck's case.

The Symptoms/Actions are:  "Harsh engagements, firm shift feel, abnormal shift schedule, abnormal torque converter clutch operation or does not engage.  May flash TCIL."

Whether or not this is your downshift problem, you certainly have a clear need to set the TP voltage.  I would try that before any further troubleshooting and see if the kickdown will restore.  If not, we can go from there.

The heater sounds like a distinct mix control issue (directing of air not occurring).  Resolving the mix control trouble should fix it.  If not, I can provide troubleshooting steps.

Moses

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