Question: I took my 2002 Ford Explorer to the repair facility with an error code of P1824. After extensive research on their part, or so they say, they stated that the electronic shift control module needed replacing so the 4x4 high light would stop blinking on the console. We have replaced this part and the light is still flashing, after unplugging battery for five minutes to reset the computer. They cannot figure out what is wrong. Any suggestions??? Answer: Replacement of the 4WD control module does not require programming using the Ford scan tool on this vehicle. Vehicles built after 03/04/2002 with the 11th digit of the VIN being (U) or vehicles built after 03/11/2002 with the 11th digit of the VIN being (Z) require a different module than those built before these dates. The modules are not interchangeable though the harness connectors will plug into either of the modules. The modules have different internal designs. The 4WD shift module is located forward of the glove box, under the passenger side of the dash. 1. Check the resistance of the magnetic clutch coil at the transfer case measuring between terminal 16 and terminal 11 of the shift motor connection. Terminal 16 connects to a Brown (BN) wire on the harness and terminal 11 connects to a Brown/Yellow (BN/YE) wire on the harness. Resistance should indicate a reading of 2.5-3.0 ohms. 2. Use a scanner to try and command the 4WD clutch on. If this is possible, monitor the voltage on the BN wire while increasing the command on the clutch. If there is low or no voltage to the clutch no matter what the command, check the powers and grounds to the module. 3. The Four Wheel Drive (4WD) module is located behind the glove box area. A. C281a pin 1 Black/White (BK/WH) and pin 2 White (WH) should be battery voltage at all times. B. Pin 9 Violet/Orange (VT/OG) should be battery voltage with the key on. C. Pin 10 Orange (OG) should be battery voltage with the key in the crank position only. D. C281b pin 16 Grey/Yellow (GY/YE) should be battery voltage with the key in the run position. 3. The grounds are C281a pin 7 Black (BK) and C281b pin 2 Black/Light Blue (BK/LB). 4. If the powers and grounds are OK, replace the 4WD module. Be sure to get the correct module, the early and late build modules will plug in but are not interchangeable.