Keep blowing fuse #9
 

I have a 1996 F150 5.0L 4R70W.

The transmission was rebuilt about 10,000 miles ago.

Previous to this problem the truck had been driving fine, only used for commuting to work and home. No off-roading, no towing.

- While driving home the engine suddenly died without warning. Towed the truck home.

- The engine would crank but not start, there was no spark at the coil. When the ignition was turned to RUN the fuel pump did not turn on.

- Spark at coil with PCM unplugged.

- Fuse #9 (30A, PCM, Fuel Pump Relay, Transmission Electronic Control) was blown. Replaced fuse.

- Truck starts and idles fine. While in PARK or NEUTRAL I can rev the engine, turn on lights, heater, press/release brake, etc. with no problems.

- With the ignition in RUN (truck off) I can put the transmission in REVERSE and the back up lights work.

- Start the truck. Use shift lever to put truck into gear with the brake pressed. Begin to release the brake to engage the transmission the truck will move a foot forward/backward (depends if in D or R) then the engine dies. Fuse #9 blown.

- Visually checked the wire harness for damage, none found.

- Use multimeter to check transmission wire harness for ground fault (open short), none found.

- Unplug solenoid connector from transmission (Shift Solenoids, Torque Converter Clutch Solenoid, Electronic Pressure Control Solenoid, Coast Solenoid). Unplug Output Speed Sensor (VSS) from transmission.

- Only the Transmission Range (TR) Sensor is still plugged in.

- Start truck, put into gear, let off brake, fuse blows. Truck did not move at all.

- Use skid steer to tow the truck into the shop. Start the truck and put into neutral to be able to use the power steering.

- Pull truck back about 10' while running in neutral, truck dies, fuse blown.

I cannot figure out what is causing the fuse to keep blowing. The truck runs and idles fine but when the transmission is engaged the fuse will blow. Do I have a bad solenoid, specifically the TCC solenoid?

Thank you for any and all help.

i would start by checking for a bad/frayed wire

9/10 times this is because of a bad transmission wiring harness - usually because the transmission shop reinstalled it improperly. We just had this problem on a buddys truck and found his harness was basically half-melted. Fuse 9 kept blowing and shifted like crap. Brand new transmission rebuild.

^keep this in mind