Code 6 - Erratic Speed Sensor While Rolling

Turn ignition off. Disconnect and then reconnect diagnostic connector (Black/Orange wire) from its mating half (Red wire). Turn ignition on. If RABS warning light illuminates, go to next step. If warning light does not illuminate, go to INTERMITTENT DIAGNOSIS .
Turn ignition off. Disconnect negative battery cable. Disconnect RABS control module connector. See COMPONENT LOCATIONS . Inspect connector for corrosion and damage. Gently pull on terminal No. 3 (Light Green/Black wire) of control module and control module harness connector. Gently pull on terminal No. 10 (Red/Pink wire) of control module and control module harness connector. See Figure .
If connector terminals are clean, fully engaged and corresponding terminal of control module are okay, leave control module disconnected and go to next step. If terminals are loose or have pulled out of connector, repair or replace terminals or connector as necessary and go to step 10). If control module terminals are loose, bent, deformed, corroded or missing, replace control module and go to step 10).
Turn ignition off. Disconnect and inspect 2-pin speed sensor connector. See Fig 1 . Inspect connector for corrosion and damage. Gently pull on both terminals of speed sensor harness connector. If terminals are clean and fully engaged in connector, reconnect sensor connector. If terminals are loose or have pulled out of connector, go to next step.
Repair or replace terminals or connector as necessary and go to step 10). If speed sensor terminals are loose, bent, deformed, corroded or missing, replace speed sensor. Reconnect sensor connector and go to step 10).
Visually inspect wire routing. If wires are properly secured and do not show signs of wear or being pinched, go to next step. If wires are not properly secured or show signs of wear or being pinched, repair as necessary and go to step 10).
Disconnect speed sensor connector. Check resistance between speed sensor terminals. If resistance is 900-2500 ohms, go to next step. If resistance is not 900-2500 ohms, replace speed sensor and go to step 10).
Check resistance between terminals No. 10 (Red/Pink wire) and No. 3 (Light Green/Black wire) of control module harness connector. See Figure . Wiggle harness. If resistance is 900-2500 ohms and steady, go to next step. If resistance is not 900-2500 ohms or is erratic, locate and repair intermittent or short/open circuit in Light Green/Black wire and/or Red/Pink wire. After repairs, go to step 10).
Ensure ignition is off. Remove speed sensor from differential assembly. Inspect sensor for build-up of metal chips on sensor magnetic pole. If no metal chips are found, leave sensor out. If metal chips are present, drain, clean and refill differential and then go to next step.
Ensure all preceding diagnostic steps have been completed and that involved wiring integrity has been verified. If steps have not been completed, go to last diagnostic step completed and continue from there. If all diagnostic steps have been completed, replace control module and go to next step. If control module has already been replaced and problem still exists, replace speed sensor and go to next step.
Turn ignition off. Reconnect negative battery cable. Ensure all connectors are properly connected and secure. Retrieve trouble codes. See RETRIEVING TROUBLE CODES . If Code 16 is present, go to CODE 16 under TEST DRIVE . If Code 6 is present, go to next step. If any other trouble code is present, go to corresponding test for appropriate trouble code.
If above steps have been completed, with no resolution, check related circuits. Go to INTERMITTENT DIAGNOSIS . If problem is found, repair damaged circuit and go to CODE 16 under TEST DRIVE . If problem is not found, go to CODE 6 under TEST DRIVE.

Fig 1: Identifying 2-Pin Speed Sensor Connector

Courtesy of FORD MOTOR CO.