Frequently Asked Questions
- Which transfer cases work with the BW-79 and FO-79?
- BW-79: Compatible with most 2011+ Borg Warner transfer cases found in Ford F-150 and Super Duty trucks (Transfer cases with a “4A” / 4-Auto setting are not supported).
- FO-79: Compatible with 2019+ Ford Ranger and 2021+ Ford Bronco transfer cases using a 5-pin plug.
- Do I have to connect the CAN Bus wiring? No. Standalone operation works with any engine/transmission setup. However, CAN Bus integration is highly recommended on 2011+ Ford automatic swaps to enable automatic, speed-safe shifting without needing to press the shift button.
- How do I shift if CAN Bus is not connected? Select your desired drive mode, then immediately press and hold the non-CAN shift button until the shift initiates.
- What are the requirements for shifting into 4 Low? The vehicle must be completely stopped, the engine at idle, and the transmission placed in Neutral with no load on the drivetrain.
Why does my transfer case shift into 4 High normally, but fails shifting into either 2 High or 4 Low with Code 2, 3, or 8?
This typically indicates that the shift motor’s position encoder is slightly out of adjustment:
- Cause: The motor is physically moving, but the internal sensor is not seeing the expected gear position within the travel window.
- Fix: Loosen the three small retaining screws on the shift motor encoder cap. Rotate the encoder slightly to align the position feedback with the controller’s expected window, then snug the screws and test the shift again.
Why does 4WD act like 2WD even though 4 Low works, or only feel like it grabs for a split second when shifting from 2WD?
You have the wrong transfer case. This happens when using an unsupported 4-Auto (Torque-on-Demand) transfer case instead of a standard mechanical unit. 4-Auto units only pulse the front wheels briefly when shifting into 4WD, and while 4 Low will physically engage
What should I do if the transfer case is binding up during shifts?
Codes 2, 3, and 8 often occur when torque or drivetrain load prevents the transfer case from completing its mechanical stroke. Ensure the transmission is in Neutral, the engine is idling, and allow the vehicle to slowly roll a few inches to relieve drivetrain bind.
Diagnostic Blink Codes
When a shift fails, the 4WD indicator light will blink a set number of times, pause, and repeat to indicate the active fault code:
| Fault Code | Description | Possible Cause | How to Clear |
| 2 | Last shift failed; returned to last position | Transfer case bound up | Next successful shift |
| 3 | Last shift failed; unable to return to last position | Transfer case bound up | Next successful shift |
| 4 | Switch circuit open (switch not detected) | Loose/broken wiring or faulty switch | Clears when fault is corrected |
| 5 | Switch circuit short | Short to ground or faulty switch | Clears when fault is corrected |
| 6 | Open motor/clutch circuit (no current draw) | Broken wiring, bad shift motor, or bad clutch | Power cycle the vehicle |
| 7 | Over-shift (motor past target position) | Intermittent encoder issue | Next successful shift |
| 8 | Not in gear (motor not completely engaged) | Transfer case bound up / encoder issue | Next successful shift |
| 9 | Encoder error (unknown motor position) | Encoder wiring failure or damaged encoder | Next successful shift |
| 10 | CAN Bus invalid gear ID | CAN Bus ID not configured | Clears when fault is corrected |
| 11 | CAN Bus invalid speed ID | CAN Bus ID not configured | Clears when fault is corrected |
| 12 | CAN Bus no communication | Wiring issue or non-compatible ECM | Power cycle the vehicle |
Common Troubleshooting Scenarios
- Indicator lights do not illuminate with ignition on:
- Verify constant 12V positive (Red wire), switched ignition power (Yellow wire), and ground (Black wire).
- If wiring has power, remove the two screws on the controller housing and inspect the internal 3-amp fuse for a short or blown filament.
- FO-79 Motor Calibration Procedure (Required after replacement/install):
- Set mode selector knob to 4WD and turn the vehicle on.
- When indicator lights flash rapidly, press the calibration button 3 times (lights will switch to a slow flash).
- Turn the selector to 2WD and wait for the shift to complete, then select 4 Low and wait for the shift.
- Success: Both lights flash together simultaneously (cycle ignition power to save).
- Failure: Lights flash alternately back and forth (return switch to 4WD and press button 3 times to retry).