Software or firmware mismatch between the Remote Function Actuation Module and another module on the network, often after a module replacement or software update.; Incorrect module installed that is not compatible with the vehicle's configuration or software level.; Corrupted software or calibration in the Remote Function Actuation Module due to a failed update or electrical glitch.; Poor electrical connections or damaged wiring at the module's connectors, causing intermittent data corruption.; A faulty Remote Function Actuation Module itself, internal hardware failure affecting software communication.; Network bus issues such as a shorted or open data line that corrupts messages and triggers incompatibility flags.; Aftermarket electronic devices improperly installed that interfere with the bus or module programming.

DTC codes / U03xx · Software and configuration mismatches / U0338

U0338Software Incompatibility With Remote Function Actuation Module

U0338 is a network communication code indicating that a control module on the vehicle's data bus has detected a software incompatibility with the Remote Function Actuation Module, which is the module responsible for keyless entry, remote start, and other remote functions. The computer has compared software version or configuration data between modules and found a mismatch that prevents proper communication or operation.

SystemNetwork

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyProfessional

AreaSoftware and configuration mismatches

Symptoms you may notice

The warning light (check engine or service vehicle soon) illuminates on the dashboard.
Remote keyless entry functions such as lock, unlock, or panic may stop working or behave erratically.
Remote start feature may be inoperative or fail to engage.
The vehicle may fail to recognize the key fob, causing a no-start condition or intermittent starting issues.
Often no symptoms besides the warning light, especially if the incompatible module is not critical to driving.
Other unrelated electrical accessories may act strangely due to bus communication interference.

Common causes, most likely first

Software or firmware mismatch between the Remote Function Actuation Module and another module on the network, often after a module replacement or software update.
Incorrect module installed that is not compatible with the vehicle's configuration or software level.
Corrupted software or calibration in the Remote Function Actuation Module due to a failed update or electrical glitch.
Poor electrical connections or damaged wiring at the module's connectors, causing intermittent data corruption.
A faulty Remote Function Actuation Module itself, internal hardware failure affecting software communication.
Network bus issues such as a shorted or open data line that corrupts messages and triggers incompatibility flags.
Aftermarket electronic devices improperly installed that interfere with the bus or module programming.

How to diagnose and fix it

Use an OBD-II scanner to retrieve all stored codes and freeze-frame data, then clear codes and test-drive to see if U0338 returns.
Inspect the Remote Function Actuation Module connectors and wiring for corrosion, loose pins, or damage, and repair as needed.
Check for technical service bulletins (TSBs) or software updates from the manufacturer that address module compatibility issues.
Reprogram or reflash the Remote Function Actuation Module with the latest software using a factory scan tool or equivalent.
If reprogramming fails, replace the Remote Function Actuation Module with a correctly matched unit and perform programming and configuration.
Verify that all modules on the network have compatible software versions and update any that are outdated.
Perform a network integrity test to ensure the data bus is free of shorts or excessive resistance that could cause communication errors.

Software Mismatch Often Misdiagnosed as Module Failure

A common cause of U0338 is installing a used or aftermarket Remote Function Actuation Module that has different software than the vehicle expects, so always verify part numbers and software compatibility before replacement.
The code can be set by a low battery or voltage spike during programming, which corrupts module memory without any hardware fault, so check battery health and charging system first.
Some vehicles require a specific sequence of module programming and initialization after replacement, and skipping steps can leave the new module incompatible and set U0338 again.
U0338 may appear alongside other U-codes indicating communication loss on the bus, which can point to a shared wiring fault rather than multiple module failures.
Do not assume the Remote Function Actuation Module is defective; often the incompatibility is with another module that was updated or replaced, so scan all modules for software version mismatches.

Can I keep driving with U0338?

The vehicle is generally safe to drive if the only symptom is the warning light and remote functions are not critical, but avoid relying on remote entry or remote start until repaired. If the vehicle fails to start or exhibits drivability issues, have it diagnosed promptly.

Tools that help

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