Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSFORD1994F 150 4WD PICKUP V8-351 5.8LREPAIR AND DIAGNOSISTRANSMISSION AND DRIVETRAINTRANSFER CASETESTING AND INSPECTIONPINPOINT TESTSTRANSFER CASE FEED HARNESS CIRCUITS
1994 Ford F 150 4WD Pickup V8-351 5.8L
Transfer Case Feed Harness Circuits
1994 Ford F 150 4WD Pickup V8-351 5.8LSECTION Transfer Case Feed Harness Circuits
Transfer Case Feed Harness Circuits
The electric transfer case feed harness contains ten wires that carry a
variety of signals to and from the electronic control module.
A listing of the transfer case feed harness circuits and their functions
follows.
1. The electro-magnetic clutch feed circuit provides a power signal to the clutch coil, from the control module when shifting from 2W to 4W drive.
2. Clockwise rotation of the electric shift motor circuit provides power to drive the shift motor through the 2H-4H-4L sequence. If a position is selected that would require a shift through an intermediate position, the module will respond as if each intermediate position was selected, even if the 4L position was commanded from 2H. It will then fulfill all of the requirements for shifting into and out of each intermediate position.
3. Counterclockwise rotation of the electric shift motor circuit provides power to drive the shift motor through the 4L-4H-2H sequence. Actuation of the low range switch, while in 4L, will cause a shift to 4H. Actuation of the "4x4" switch, after a shift to 4H from 4L, will then cause a shift to 2H.
4. The speed sensor coil feed circuit provides a constant signal from the electronic control module to the speed sensor located in the transfer case.
5. The speed sensor coil return circuit provides a varying signal (while the vehicle is in motion) from the speed sensor to the electronic control module. This signal indicates the vehicle speed to the microprocessor so that it can control the application of the LOW RANGE gear selection in the transfer case.
6. The shift position sensor feed circuit provides a power signal from the electronic control module to the shift position sensor to energize the sensor.
7. Shift position sensor return circuits provide the output information signals from the transfer case to the electronic control module. This information gives the control module the correct position of the shaft that turns the helical cam in the transfer case.
The electric transfer case feed harness contains ten wires that carry a
variety of signals to and from the electronic control module.
A listing of the transfer case feed harness circuits and their functions
follows.
1. The electro-magnetic clutch feed circuit provides a power signal to the clutch coil, from the control module when shifting from 2W to 4W drive.
2. Clockwise rotation of the electric shift motor circuit provides power to drive the shift motor through the 2H-4H-4L sequence. If a position is selected that would require a shift through an intermediate position, the module will respond as if each intermediate position was selected, even if the 4L position was commanded from 2H. It will then fulfill all of the requirements for shifting into and out of each intermediate position.
3. Counterclockwise rotation of the electric shift motor circuit provides power to drive the shift motor through the 4L-4H-2H sequence. Actuation of the low range switch, while in 4L, will cause a shift to 4H. Actuation of the "4x4" switch, after a shift to 4H from 4L, will then cause a shift to 2H.
4. The speed sensor coil feed circuit provides a constant signal from the electronic control module to the speed sensor located in the transfer case.
5. The speed sensor coil return circuit provides a varying signal (while the vehicle is in motion) from the speed sensor to the electronic control module. This signal indicates the vehicle speed to the microprocessor so that it can control the application of the LOW RANGE gear selection in the transfer case.
6. The shift position sensor feed circuit provides a power signal from the electronic control module to the shift position sensor to energize the sensor.
7. Shift position sensor return circuits provide the output information signals from the transfer case to the electronic control module. This information gives the control module the correct position of the shaft that turns the helical cam in the transfer case.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.