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DTC codes / C03xx · Brakes, steering and suspension / C0387

C0387Transfer Case Position Sensor

C0387 indicates that the transfer case position sensor circuit has a fault, meaning the control module cannot reliably determine whether the transfer case is in two-wheel drive, four-wheel drive, or neutral. The computer detects an abnormal voltage or signal from the sensor that falls outside the expected range for the current operating conditions.

SystemChassis
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaBrakes, steering and suspension

Symptoms you may notice

  • Often no symptoms besides the warning light, especially if the vehicle remains in a default drive mode
  • Four-wheel-drive or low-range indicator flashing or failing to illuminate when selected
  • Transfer case refuses to shift into or out of four-wheel drive, or shifts unexpectedly
  • Service four-wheel-drive or traction control warning message displayed on the dash
  • Reduced engine power or disabled stability control in some vehicles as a fail-safe

Common causes, most likely first

  1. Faulty transfer case position sensor or encoder ring
  2. Damaged, corroded, or disconnected wiring harness at the transfer case
  3. Poor electrical connection at the sensor or control module connector
  4. Failed transfer case control module or four-wheel-drive control module
  5. Mechanical binding or damage inside the transfer case preventing proper sensor movement
  6. Water intrusion or debris contaminating the sensor connector

How to diagnose and fix it

  1. Scan all modules for stored and pending codes, and record freeze-frame data to understand when the fault occurs
  2. Inspect the transfer case position sensor connector and wiring for corrosion, chafing, or loose pins
  3. Check sensor reference voltage and ground at the connector with a multimeter, comparing to manufacturer specifications
  4. Test the sensor signal output through its full range of motion, either by shifting the transfer case or using a scan tool to command positions
  5. Verify that the transfer case actually shifts mechanically and that the sensor linkage or encoder is not binding
  6. If the sensor tests out of specification, replace it and clear codes, then perform a transfer case calibration or relearn if required
  7. If the sensor and wiring are good, diagnose the control module and its power and ground feeds before condemning it

Before you replace the transfer case sensor

  • A loose or corroded ground at the transfer case can mimic a failed sensor, so always load-test the ground circuit before condemning the sensor.
  • On many vehicles, the transfer case position sensor is integrated into a motor actuator assembly, and a faulty actuator can set this code without any sensor problem.
  • After replacing the sensor, some transfer case control modules require a relearn or calibration procedure; skipping it can leave the code active even with good parts.
  • Intermittent faults often occur only when the transfer case is hot or after driving in wet conditions, so a cold static test may pass while the fault is still present.
  • A weak battery or low charging voltage can cause the control module to misread the sensor signal, so check battery health before chasing the circuit.

Can I keep driving with C0387?

You can usually drive the vehicle in two-wheel drive without immediate risk, but avoid relying on four-wheel drive and do not tow or drive in low-traction conditions until the fault is repaired. If the transfer case is stuck in neutral or four-wheel drive, limit driving to low speeds and have it serviced promptly.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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