P1528 on GM vehicles indicates the powertrain control module (PCM) has detected a fault in the governor circuit, which is part of the transmission's hydraulic control system. The governor is responsible for generating a pressure signal proportional to vehicle speed, and the PCM uses this signal to manage shift timing and line pressure. When the circuit is out of range, the PCM sets this code and may default to a limp-home mode.
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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