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.
Electronic Shift-On-The-Fly (ESOF) System
The Electronic Shift-On-The-Fly (ESOF) system consists of the following components:
- MSS
- TCCM (located near the passenger kick panel)
- IWE solenoid (located on cowl near brake booster)
- (2) IWE vacuum actuators (one on each front hub)
- (2) IWE clutch rings (one on each front hub)
- 4WD mode indicators and messages in the IPC message center
- Transfer case with shift motor and synchronization clutch
Vehicles equipped with the Electronic Shift On-The-Fly (ESOF) system can operate in 2WD (2H), 4WD High (4H), or 4WD low (4L). When shifting into or out of 4WD (4L) range, the TCCM requires that the vehicle speed is less than 5 km/h (3 mph) and the transmission is in NEUTRAL.
The transfer case is equipped with an electronically controlled clutch which is located inside the case. This clutch is used to synchronize the speed of the front driveline with the rear driveline during 2WD (2H) to 4WD High (4H) shifts.
The transfer case is shifted electronically based on the MSS (Mode Select Switch) input.
For additional information, refer to: Four-Wheel Drive Systems - System Operation and Component Description .
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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.