P0601: OBD-II code P0601 means the PCM has detected a memory checksum error inside itself — its stored calibration data may be corrupted.

Symptoms

• Check engine light is on; the vehicle may run poorly, stall randomly, or refuse to start.
• The code returns immediately after clearing while the checksum error persists.
• Multiple unrelated codes may set together as the corrupted PCM misinterprets sensor inputs.

Common causes

• Genuine internal PCM memory failure — usually needs replacement or professional rebuild.
• Corrupted PCM firmware from a botched reflash or a power loss during a programming session.
• Low or unstable battery voltage repeatedly tripping the module's memory integrity check.

What to do?

Verify battery voltage is 12.4 V+ at rest and 13.8-14.5 V running. If voltage is good and P0601 will not clear, the PCM needs replacement or a professional rebuild, followed by programming to the vehicle's VIN and options.