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.
Theory Of Operation
DH8 = Full-Time Active Transfer Case. DH9 = Part-Time Transfer Case.
Active Transfer Case (DH8) - Range Position Sensor: The Transfer Case Range Position Sensor is a serviceable component located on the right side of the Transfer Case. There are three circuits between the sensor and the Drivetrain Control Module (DTCM):
- 5-Volt Supply
- Sensor Ground
- Signal
The Range Position Sensor transmits a PWM signal at 500hz to the DTCM on the Signal circuit. The PWM signal is relative to the position of the sensor plunger that contacts a Sense Plate that is attached to the Dual Drive Gear.
| Range Position | Minimum Duty Cycle (%) | Nominal Duty Cycle (%) | Maximum Duty Cycle (%) |
|---|---|---|---|
| HI Range (2WD, 4WD HI, 4WD Auto) |
10.5% | 12.5% | 14.5% |
| Neutral | 48.0% | 50.0% | 52.0% |
| 4WD Lo | 85.5% | 87.5% | 89.5% |
The PWM signal can be converted to an average voltage that can be measured with a Digital Multimeter (DMM).
| Range Position | Minimum Average Voltage | Nominal Average Voltage | Maximum Average Voltage |
|---|---|---|---|
| HI Range (2WD, 4WD HI, 4WD Auto) See note below |
0.525v | 0.625v | 0.725v |
| Neutral | 2.40v | 2.50v | 2.60v |
| 4WD Lo | 4.275v | 4.375v | 4.475v |
The DTCM monitors the signal from the two hall effect sensors inside the shift motor to determine if the Transfer Case is in 2WD, 4WD HI, or 4WD Auto mode position.
Part-Time Transfer Case (DH9) - Motor Position Encoder: The Motor Position Encoder is not a serviceable component of the Transfer Case Shift Motor. The motor only rotates a partial revolution throughout its travel to engage the Mode and Range forks. There are five encoder related circuits between the Shift Motor and DTCM:
- 5-Volt Supply
- Encoder Signal 0
- Encoder Signal 1
- Encoder Signal 2
- Encoder Signal 3
An encoder disc rotates with the motor armature. As the disc rotates, a combination of the four encoder sensor signal lines are connected through a common internal circuit that pulls the voltage down to indicate the motor position. The motor position is relative to the Mode and Range fork positions inside 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.