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I have a 94 F-350 dually crew cab with 89Kmi, question is does a burned out 3rd brake light (above the rear window) affect the trans ? I had water in the light, sadly I never drive the truck but the last time I did it was acting like the FIPL was bad or out of adjustment, it would occasionally kick out of OD, the FIPL replaced somewhere around 60Kmi....thanks in advance!!
 

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It doesn't effect shifting, but assuming the design is the same as later powerstrokes, what happens is the turn signal switch, also known as the multifunction switch goes bad and voltage spikes burn out the center bulb, then after the bulb is burned out there is no load to keep the spikes from confusing the whole system. Cruise control will shut off at random times, transmission will have the torque converter unlock. In other words the multifunction switch is bad and the truck thinks the brakes are being applied. The center bulb burns out first, then the transmission problems, but it's not the bulb, it's the switch causing the bulb to go bad.
 

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Yes, any fault in the brake light circuit CAN affect an E4OD. This diagram shows, and its caption explains everything that affects a Ford electronic automatic:



This one describes a very simple but important diagnostic test for electronic automatics using only the brake pedal:



Since an intact incandescent bulb is required to supply a weak ground to the EEC to indicate BOO off, a burned-out bulb can cause static voltage to trigger unwanted TCC activity.
 
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