Pinpoint Test M: P1839:00, P1840:00, P1841

WARNING: This page is about a different car, the 2021 Ford F-150. However, it is still accessible from the selected car via links, so may be relevant.

Refer to Wiring Diagrams Two Wheel Drive/Four Wheel Drive Systems for schematic and connector information.

Normal Operation and Fault Conditions

The electric shift motor is mounted externally to the transfer case. It drives a rotary cam which moves the mode fork within the transfer case. The shift motor moves during shifts in to and out of 4L, and to Neutral. It does not move during the shift between 2H and 4A or 4A to 4H. TCCM directly controls the electric shift motor and can reverse motor polarity to reverse rotary cam/shift fork direction. The TCCM monitors the transfer case shift motor circuits for open, short to ground, and short to voltage.

DTC Fault Trigger Conditions

DTC	Description	Fault Trigger Condition
TCCM P1839:00	Transfer Case Shift Motor Open Circuit: No Sub Type Information	This DTC sets when the TCCM detects an open circuit to the shift motor.
TCCM P1840:00	Transfer Case Shift Motor Short Circuit To Battery: No Sub Type Information	This DTC sets when TCCM detects a short to voltage. Shift motor moves are prevented when this DTC is set.
TCCM P1841:00	Transfer Case Shift Motor Short Circuit To Ground: No Sub Type Information	This DTC sets when TCCM detects a short to ground. Shift motor moves are prevented when this DTC is set.

Possible Sources

Wiring, terminals or connectors
Shift motor
TCCM

M1 CHECK THE TRANSFER CASE SHIFT MOTOR CIRCUITS FOR AN OPEN

Disconnect Transfer Case C350.

Disconnect TCCM C2371B.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C2371B-1	Courtesy of FORD MOTOR COMPANY	C350-4
C2371B-2	Courtesy of FORD MOTOR COMPANY	C350-3

Are the resistances less than 3 ohms?

Yes

GO to M2

No	REPAIR the open circuit.

M2 CHECK THE TRANSFER CASE SHIFT MOTOR CIRCUITS FOR SHORT TO VOLTAGE

Ignition ON.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C2371B-1	Courtesy of FORD MOTOR COMPANY	Ground
C2371B-1	Courtesy of FORD MOTOR COMPANY	Ground

Is any voltage present?

Yes	REPAIR the short to voltage.

GO to M3

M3 CHECK THE TRANSFER CASE SHIFT MOTOR CIRCUITS FOR SHORT TO GROUND

Ignition OFF.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C2371B-1	Courtesy of FORD MOTOR COMPANY	Ground
C2371B-2	Courtesy of FORD MOTOR COMPANY	Ground

Are the resistances greater than 10, 000 ohms?

Yes	INSTALL a new transfer case shift motor. REFER to: Transfer Case Shift Motor .

No	REPAIR the short to ground.