U0579 indicates that the Powertrain Control Module (PCM) has detected invalid or out‑of‑range data coming from the Seat Occupancy Module (sometimes referred to as the Seat Module L). This typically means communication on the vehicle’s CAN bus is corrupted or the seat module is not responding correctly.
The module itself has failed internally, sending corrupted data or no data at all to the PCM.
Corroded pins, broken wires, or loose connectors in the seat module circuit can cause intermittent or invalid signals.
High‑frequency noise, grounding issues, or a short to voltage on the bus can corrupt data packets from the seat module.
A recent software update that did not correctly map the seat module data can produce invalid‑data flags.
Only after ruling out the module, wiring, and bus issues should a PCM failure be considered, as it is an uncommon cause.
Replacing the PCM is rarely the correct solution. In most cases the problem lies with the seat module, its wiring, or the CAN‑bus. PCM replacement should only be considered after exhaustive testing of those areas.
The PCM may disable the supplemental restraint system if it cannot verify a valid seat occupancy signal, which can prevent the airbag from deploying in a crash.
Both are possible. Intermittent wiring issues or a marginal seat module can cause occasional trips, while a completely failed module will store the code continuously.
Yes. After correcting the fault, clear the code with a scan tool and then drive the vehicle through a complete drive cycle to verify that the code does not return.