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Q: After a complete rearend swap,car wouldn't start due to pats(flashing red threat light

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6 weeks ago, my differential broke and all I could afford was a used(high mileage ) complete rear end from a junk yard ($100 ).now it wouldn't start up and the red theft light was flashing very fast! And for the next few days it wouldn't start and the theft light continued to flash fast whenever we tried to start it. also peculiar is the odometer mileage completely disappeared and was replaced by eight # 8's(8888888)(key in on-run position/engine dormant) and changed to 8 dashes( --------)(key in start position/engine rotating) so a friend of a friend (after a routine check) was positive that the " no start" with "red flashing theft llighy was that fuel pump was no good, so he changed fuel pump and then the truck would start as always. Now after rearend swap, the theft light started flashing again so again it won't start ! this is my only truck and I use it mainly to get grandchildren to school and back, buy groceries,

My car has 125000 miles.
My car has an automatic transmission.

Hi there:

It’s quite possible that while swapping out the rear end, the battery cables were not disconnected; which may have shorted out a few electrical components; perhaps even the ECU. There are a few sensors attached to the rear end differential on the 2001 Ford Expedition that may not properly align with the replacement rear end you got from the junk yard. When you have major electrical failures as you’ve described, it’s best to contact a professional mobile mechanic and have them come to your location and complete a check engine light inspection first. This will allow them to download all stored error codes in your Expedition and determine what is faulty, damaged or needs to be repaired in order to fix your Ford.

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