I just replaced the power steering pump on my 2001 F150 SuperCrew, it has the 4.6L V8. Once the new pump was on, we reassembled it and now it wont start. It cranks but wont start. There has previously been a Viper alarm system on it, a remote start system and custom wiring for trailer lights, but NONE of those are present anymore. There is a wire that seems to be run alongside the wire going to the oil sending unit, but the second plug doesnt have anywhere to plug into. When trying to start the truck the "dummy" THEFT light turns on and starts flashing repeatedly until you turnt he truck completely off. Does anyone know what to do so I can get my truck running again?

 

I can only offer some guess as to what to look at.
Since you had the drive belt off or loose, look at he crank position sensor plug for being loose or off.
Next look at the cam position sensor plug for the same.
Both these could have been hit by the belt or work done.
Loss of either one means a no start condition.
The PATS needs to communicate with the PCM. If the PCM is not responding, the PATS can get a little "upset" hi hi.
BTW, if you turn on the ignition and not crank the motor, after about 1 minute or so the T lamp 'may' flash at a fast rate.
The code would be a hint as to what is 'not' happening. But you would need that extra info to be able to see what the code is from the 'dash' diagnostics once your triggered that function into operation.
There is often more help than meets the eye if you are awhere of how to get and interpet it.
Good luck.