U0437 indicates that a vehicle control module (typically the PCM, TCM, or body control module) received invalid or corrupted data from the rear differential control module over the CAN bus network. This is a network communication fault, not a mechanical differential failure. The receiving module cannot trust the data from the rear differential module, so it sets this code and may illuminate warning lights.
The rear differential control module itself has internal electrical failure, producing invalid data. This is the most common root cause.
Physical damage, chafing, or corrosion in the wiring between the rear differential module and the CAN bus network, causing data corruption.
Poor electrical connections at the rear differential module connector or the network junction, leading to signal degradation.
Failed wheel speed sensors, differential engagement sensor, or position sensor sending erroneous data that the module cannot process correctly.
Another module on the network is faulty or creating bus errors that affect data integrity for the rear differential module.
Rare. The receiving module may have a software bug or hardware fault in its network interface. Almost never the cause despite what some sources may claim.
Almost never. The PCM/ECM is the receiver of invalid data, not the source. Replacing it will not fix the communication problem from the rear differential module. This is one of the most commonly misdiagnosed codes—always diagnose the rear differential module and its wiring first.
No. U0437 is an electrical/communication fault. The rear differential itself may be mechanically fine; the issue is the control module reporting invalid data over the network.
Vehicle behavior varies. You may experience reduced traction control, stability system faults, or limp mode. If the rear differential fails to engage, especially in AWD/4WD vehicles, drivability and safety may be compromised in certain conditions.