P1838

What it means

P1838 on a Lincoln means the control module has detected a fault in the circuit for the transfer case shift motor, which moves the transfer case between drive ranges on four-wheel-drive models. The module commands the motor and monitors its circuit and position feedback, and it set the code because the electrical behaviour or response did not match what it expected. Exact circuit layout and the module that sets the code depend on the model and year.

Symptoms

• 4WD indicator light flashing, staying on or showing a fault message
• Transfer case will not shift between 2WD and 4WD or between high and low range
• Shift attempts are slow, noisy or stop part way
• Four-wheel drive unavailable or stuck in one mode
• Warning lamp or stored fault code with no obvious change in drive feel

Possible causes

• Damaged, corroded or loose wiring or connector at the transfer case shift motorlikely
• Failed transfer case shift motor or its internal position sensor or encoderlikely
• Open circuit, short to ground or short to power in the motor wiring harnesspossible
• Low battery voltage or poor power and earth supply to the shift motor circuitpossible
• Faulty transfer case control module or driver circuitrare
• Mechanical binding inside the transfer case overloading the motorrare

How to diagnose

1. Read all stored codes and freeze frame data, noting any other 4WD or transmission codes, then record and clear only to see if P1838 returns
2. Check battery condition and charging voltage, as low voltage can upset the shift motor circuit
3. Inspect the shift motor wiring and connector at the transfer case for water ingress, corrosion, chafing, heat damage and pushed-out pins
4. Check the relevant fuses and relays for the transfer case control circuit against the wiring diagram for your model
5. Test the circuit for continuity, shorts to ground and shorts to power, and check the supply and earth at the motor connector
6. Use a scan tool that supports the transfer case to command the motor and watch the position feedback and live data for a response
7. Measure motor and position sensor resistance or signal against the manufacturer specification for your model
8. If the circuit and motor test good, check for mechanical binding in the transfer case and only then consider the control module

How to fix

• Repair or replace damaged wiring and clean or replace corroded connectors and terminals
• Replace the transfer case shift motor or encoder assembly if it fails testing
• Restore proper power and earth supply, including replacing faulty fuses or relays once the cause of failure is found
• Correct any battery or charging system fault
• Repair any internal transfer case mechanical fault that is overloading the motor
• Replace or reprogram the control module only after the wiring and motor have been proven good

Can I keep driving?

This code for other makes

• P1838FordTransmission Transfer Case Shift Motor Circuit Failure
• P1838MercuryTransmission Transfer Case Shift Motor Circuit Failure
• P1838OtherTransmission Transfer Case Shift Motor Circuit Failure

Nearby codes

• P1834LincolnTransmission Transfer Case Differential Lock-Up Solenoid Short Circuit To Battery
• P1846LincolnTransmission Transfer Case Contact Plate A Circuit Failure