Sensor

Tiny
RLOVE34
  • MEMBER
  • 1999 FORD EXPEDITION
  • 185,000 MILES
I put my truck in reverse and it blows the #24 fuse. But when I change the fuse and go forward it runs fine. It only blows when im backing up or putting it in reverse. I have changed the #304 relay and checked the rest of my fuses all are good. #24 is the only fuse that will blow everytime. Very stressful please hel
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Friday, May 3rd, 2013 AT 6:02 PM

6 Replies

Tiny
ASEMASTER6371
  • EXPERT
Park neutral switch on the side of the trans.

Roy
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Friday, May 3rd, 2013 AT 7:06 PM
Tiny
CARADIODOC
  • EXPERT
In this case you have to determine how the short occurs. If the fuse blows as soon as you shift into reverse, even when the engine is not running, that is different than if the engine has to rock from being shifted into reverse while it's running. Rocking suggests a wire is rubbed through and grounding out so you would look for wire harnesses that move when you shift between drive and reverse.

Either way, a simple trick to finding a short is to replace the blown fuse with a pair of spade terminals, then use small jumper wires to connect them to a 12 volt light bulb. A brake light bulb works well. When the circuit is live and the short is present, the bulb will be full brightness and hot so be sure it's not laying on the carpet or against a plastic door panel. Now you can unplug electrical connectors and move things around to see what makes the short go away. When it does, the bulb will get dim or go out.
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Friday, May 3rd, 2013 AT 7:26 PM
Tiny
RLOVE34
  • MEMBER
Could it be the park neutral switch or the speed sensor?
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Friday, May 3rd, 2013 AT 7:40 PM
Tiny
CARADIODOC
  • EXPERT
The speed sensor has nothing to do with any fused circuit.

What is fuse 24 for? What doesn't work when it blows?
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Friday, May 3rd, 2013 AT 7:55 PM
Tiny
RLOVE34
  • MEMBER
Fuse #24 is the powertrain control moduel for automatic transsmission. When I put it in reverse and start backing up it blows and the trans dont run right or shift right. I can smell the truck fluiding. But if I change tge blown fuse it runs perfect. Until I have to back up the transmission dont run right.
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Friday, May 3rd, 2013 AT 8:06 PM
Tiny
CARADIODOC
  • EXPERT
I'd go back to my original recommendation of replacing the fuse with a small 12 volt light bulb. You have the advantage that you know how to make the short occur. When it does, the bulb will limit current flow to a safe level. It will, however, also limit current to such a low level that the computer may not work right. In that case you would need to use a larger bulb that will allow more current to flow. A head light bulb will pass about five amps.
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Friday, May 3rd, 2013 AT 8:30 PM

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