U0553 is a network communication diagnostic trouble code indicating that a master module (typically the body control module or other gateway module) has received invalid or corrupted data from the Rear Lighting Control Module B over the vehicle's CAN bus communication network. The 'invalid data' designation means the message structure, timing, or content from that module failed the receiving module's validation checks, rather than the data being simply absent. This code is commonly seen on vehicles that use distributed lighting control architecture with multiple rear lighting modules.
Corroded, loose, or damaged pins in the module's connector, or chafed/broken wiring between the module and the CAN bus, are the most common cause. Moisture intrusion at rear-mounted connectors is a frequent contributor.
A blown fuse, failed ground strap, or corroded power feed can cause the module to transmit erratic or invalid messages. Voltage drop testing at the module connector is the standard check.
The module itself can develop internal faults that produce out-of-specification CAN messages. This is less common than wiring issues but should be considered after the harness is verified.
Excessive resistance, a short to ground or power on the CAN lines, or a faulty terminating resistor can corrupt data from any module on the segment, including the rear lighting module.
An outdated, corrupted, or incorrectly flashed calibration can cause a module to transmit messages that fail the receiver's validation. A reflash or reprogramming may resolve it.
In rare cases the receiving module (often the BCM) misinterprets a valid message as invalid. This is the least likely cause and should only be pursued after ruling out the module on the other end and the wiring.
In most cases the vehicle remains drivable, but rear lighting functions may be unreliable, which can be a safety concern. Address it promptly, especially if rear lights, brake lights, or turn signals are affected.
No. The code specifically points to data coming from the Rear Lighting Control Module B being invalid, which almost always traces to wiring, power/ground, network issues, or the rear lighting module itself. Replacing the BCM or PCM is an expensive step that is almost never the correct fix for this code.
Clearing the code is a reasonable first step to confirm whether the fault is intermittent or hard-fault. If it returns quickly, the underlying condition is still present and requires diagnosis; clearing it does not fix the root cause.
When a CAN network has a wiring or termination fault, multiple modules on the same bus segment can simultaneously set communication codes. Treating U0553 as the only code and ignoring others can lead to missed root-cause issues on the shared network.