P0602: OBD-II code P0602 means the PCM has detected it wasn't programmed correctly for this vehicle — either the flash was incomplete or the VIN and options data are missing.

Symptoms

• Check engine light is on; the vehicle may run poorly, refuse to start, or default to a generic calibration.
• The code appears after a PCM replacement or reflash that wasn't completed properly.
• Multiple companion codes may set as the PCM defaults or refuses to run emissions monitors.

Common causes

• An interrupted or incomplete PCM reflash session, often caused by low battery voltage during programming.
• A PCM installed from another vehicle without being properly programmed to this one's VIN and options.
• A software mismatch between the PCM's calibration and the vehicle's other modules after a partial reflash.

What to do?

Take the vehicle to a shop with OEM programming capability. Perform a full PCM reflash with the correct calibration for the VIN. Ensure battery voltage is maintained during programming (use a memory saver or battery maintainer).