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Ron
Ron, ASE Certified Technician
Category: Ford
Satisfied Customers: 33417
Experience:  23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
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MY 1999 FORD EXPEDITION HAS A BLINKING 4X4 LIGHT-THE 4 ...

Resolved Question:

MY 1999 FORD EXPEDITION HAS A BLINKING 4X4 LIGHT-THEXXXXXIS WORKING OK. ANY SOLUTION. IS THIS GOING TO CAUSE A PROBLEM?
Submitted: 8 years ago.
Category: Ford
Expert:  Ron replied 8 years ago.

HiCustomer

The light flashing means the 4x4 system sees something out of range and it often times is a speed sensor. To determine which one is is you should start with having the system scanned and the code retrieved.The transfer case speed sensors provide a square wave signal to the GEM indicating drive shaft output speed. If the GEM detects that one sensor is indicating a lower input than the other, it will control a hydraulic clutch inside the transfer case with a stronger duty cycle command signal (on a Brown (BN) wire) to provide more output torque to the front drive shaft.

Inspect the wiring of the front and rear drive shaft speed sensors located on the transfer case for an intermittent open, chafe to ground or connection problem at the transfer case shift motor connection.

If the circuits appear to be in good condition, suspect that one or both of the sensors is intermittently failing thereby causing the codes to set.

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