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DTC codes / U01xx · Lost communication with a control module / U014D

U014DLost Communication with Mirror Control Module B

U014D is a generic network communication code indicating that the primary control module (often the body control module or gateway) has lost contact with the mirror control module B over the vehicle's data bus. The computer detects this when it sends periodic messages to the mirror module and receives no response within a set time, or when the module fails to report its status.

SystemNetwork
Code typeGeneric (all makes)
SeverityLow
Fix difficultyIntermediate
AreaLost communication with a control module

Symptoms you may notice

  • The power mirrors may not adjust in one or more directions, or may not fold or dim as intended.
  • Memory mirror settings may not recall correctly, or the mirror may not return to its saved position.
  • A warning light or message on the dash, such as a communication fault or service indicator.
  • Often no symptoms besides the warning light, especially if the mirror module is only used for non-critical features.
  • Intermittent operation of mirror functions, sometimes working and sometimes not, especially over bumps or in wet weather.
  • Other unrelated electrical gremlins, such as interior lights or door locks acting oddly, if the fault lies on a shared bus.

Common causes, most likely first

  1. A blown fuse or poor connection at the mirror control module B power or ground circuit.
  2. Damaged or corroded wiring or connectors between the mirror module and the data bus, often in the door jamb or mirror housing.
  3. A faulty mirror control module B itself, due to internal failure or water intrusion.
  4. A short or open in the data bus wiring that affects communication with that module.
  5. Low battery voltage or a weak battery causing modules to drop offline intermittently.
  6. A software glitch or corrupted configuration in the mirror module or gateway that requires reflashing or reinitialization.
  7. Aftermarket accessories or improper repairs that tapped into the mirror circuit and disturbed communication.

How to diagnose and fix it

  1. Verify the battery is fully charged and in good condition, as low voltage is a common cause of communication codes.
  2. Check all fuses related to the mirror control module and the data bus, and replace any that are blown.
  3. Inspect the wiring and connectors at the mirror module, door jamb, and any inline connectors for damage, corrosion, or loose pins.
  4. Use a scan tool to clear the code and see if it returns immediately; if it does, perform a bidirectional test to confirm the module is unresponsive.
  5. Measure voltage and ground at the mirror module connector with the key on, and compare with factory specifications.
  6. Check the data bus voltage or resistance at the module connector to rule out a bus fault, following the manufacturer's diagnostic procedure.
  7. If all electrical checks pass, substitute a known-good module or reflash the existing module as the final step before replacement.

What most technicians overlook with U014D

  • A weak or failing battery often causes this code because modules drop offline when voltage dips during cranking, and the code sets even though the mirror module is fine.
  • Water intrusion into the mirror housing or door connector is a frequent hidden cause, especially on vehicles with power-folding mirrors, and visual inspection may not reveal it until the connector is opened.
  • The code can be set by a fault in the gateway module or a shared bus segment, so replacing the mirror module without checking bus integrity can be a costly misdiagnosis.
  • Some vehicles require the mirror module to be initialized or configured after replacement, and skipping this step will leave the code stored even with a new module.
  • Intermittent U014D codes that appear only in cold or wet weather often point to a marginal connection rather than a failed module, so wiggle tests and voltage drop checks are more useful than parts swapping.

Can I keep driving with U014D?

You can generally continue driving safely because the mirror control module is not critical to engine or brake operation, but avoid relying on power mirror functions and address the fault soon to prevent further electrical issues. If the code is accompanied by other communication codes or drivability symptoms, have it diagnosed 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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