Pinpoint Test A: The 4-Wheel Drive (4WD) Control Module Does Not Respond To The Diagnostic Tool

WARNING: This page is about a different car, the 2005 Ford Pickup, 2005 Ford F550 Super Duty, 2005 Ford F450 Super Duty, and 2005 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.

A1 CHECK THE 4WD CONTROL MODULE C281B FOR DAMAGE
- Key in OFF position.
- Disconnect: 4WD Control Module C281b.
- Inspect the 4WD control module C281b for damage.
- Is the 4WD control module C281b OK?
- Yes : GO to A2.
- No : REPAIR the 4WD control module C281b as necessary. CARRY OUT the data link diagnostics test.
A2 CHECK CIRCUIT 70 (LB/WH) FOR AN OPEN BETWEEN THE DATA LINK CONNECTOR (DLC) C251 AND THE 4WD CONTROL MODULE C281B
- Measure the resistance between the 4WD control module C281b pin 10, circuit 70 (LB/WH), harness side and the DLC C251 pin 7, circuit 70 (LB/WH), harness side.
  
  Fig 1: Check Circuit 70 (LB/WH) For An Open Between The Data Link Connector (DLC) C251 And The 4WD Control Module C281B
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
- Yes : GO to A3.
- No : REPAIR the circuit. CARRY OUT the data link diagnostics test.
A3 CHECK FOR CORRECT 4WD CONTROL MODULE OPERATION
- Disconnect all the 4WD control module connectors.
- Check for:
  - corrosion
  - pushed-out pins
- Connect all the 4WD control module connectors and make sure they seat correctly.
- Operate the system and verify the concern is still present.
- Is the concern still present?
- Yes : INSTALL a new 4WD control module. REFER to FOUR- WHEEL DRIVE SYSTEMS . CARRY OUT the data link diagnostics test.
- No : The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the diagnostic trouble codes (DTCs). REPEAT the self-test.