Rick's Free Auto Repair Advice

Transfer case shifts on its own

Diagnose and fix transfer case shifts on its own

Ford has issued a service bulletin #01-14-1 to addresses a transfers case shifts on its own condition on the vehicles listed below. The affected vehicles may exhibit inadvertent 4X4 Hi or Low shift events, 4X4 and/or Low Range indicator flashing or solid or vehicle stuck in 4L after an uncommanded shift. This may be caused by the 4X4 shift motor. The bulletin applies only to Ford F-150 pickup with electronic shift on the fly (ESOF) transfer case and results in unintended shift into 4×4 Hi or Low.

Transfer Case Shifts on its own trouble codes

An uncommanded 4H or 4L shift due transfer case shift on its own is caused by a false shift motor contact plate signal may or may not be accompanied by one or more of these trouble codes, depending on whether the ignition key was cycled after the shift event.

P1838 Transmission Transfer Case Shift Motor Circuit Failure
P1846 Transmission Transfer Case Contact Plate ‘A’ Circuit Failure
P1850 Transmission Transfer Case Contact Plate ‘B’ Circuit Failure
P1854 Transmission Transfer Case Contact Plate ‘C’ Circuit Failure
P1858 Transmission Transfer Case Contact Plate ‘D’ Circuit Failure
P1867 Transmission Transfer Case Contact Plate General Circuit k Failure

Vehicles affected by the transfer case shifts on its own flaw

1999 F-250 LD

1999-2001 EXPEDITION, F-150


Symptoms caused

You may notice these symptoms when the shift motor performs an uncommanded low speed shift to 4L event:

• The front end binds or hops while turning

• You feel binding in the drivetrain when backing up and/or turning

• You hear an audible clunking or grinding noises, or the amber low range light is on

When the uncommanded transfer case shifts on its own happens

The Generic Electronic Module (GEM) can receive a false Mode Switch input during or shortly after the Digital Transmission Range Sensor (DTR) indicates a Neutral range pass-thru. An uncommanded shift is possible if remaining 4L pre-conditions are met. The pre-conditions, besides transmission in Neutral range, include: brake depressed and vehicle speed is less than 3 mph. A false switch input may also set a P1812 or P1815 DTC in the GEM.

Check the mode switch circuits 682 (dark blue) for short to power and 780 (dark blue) for ground short, loose connections at inline connectors, or wire chaffing.

Check the Monitor Mode Switch Parameter Identification Display (PID) 4WD_SW for false readings while slightly pushing in and wiggling the mode switch knob.

Replace the Mode Switch if it fails testing or repair wiring on circuits 682 or 780 if fault indicated. If the tests pass, inspect build date stamped on the GEM and replace if GEM built prior to 9/98.

Other transfer case shifts on its own related symptoms

If you experience an uncommanded shift to 4L you may notice:
• Rapid deceleration
• High engine revving possibly accompanied by a P1270 DTC in the PCM
• Clunk/grind noise
• Speedometer may spike higher than actual speed.

How to fix transfer case shifts on its own

These trucks are equipped with the Borg-Warner


OLD VERSION F75Z-7G360-A causes the problem

44-06 transfer case. Ford has issued a new shift motor # YL1Z-7G360-AA shift motor for vehicles built before 12/99. The YL1Z-7G360-AA shift motor with a grey contact plate cover replaces the prior design F75Z-7G360-AA motor with a blue contact plate cover.

transfer case shift motor

New YL1Z-7G360-AA shift motor solves the problem

The Grey cover shift motors contain improved sense plate material and shift motor terminal upgrade.

©, 2018 Rick Muscoplat


Posted on by Rick Muscoplat

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