P1609 on a GM vehicle means the powertrain control module (PCM) has lost the serial data stream it expects from the traction control system (TCS) module over the controller area network (CAN) or class 2 data bus. The PCM sets this code when it stops receiving the periodic TCS status and wheel-speed messages it needs to coordinate torque management, and it may also illuminate the ABS and TCS warning lamps.
Guidance is general and written for GM vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.
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