P0601: Internal Control Module Memory Checksum Error

What does P0601 mean?

The module continuously calculates a checksum over its program and calibration memory (flash) and compares it with the stored value; on newer units the flash error correction also reports bit errors it cannot repair. A mismatch means the stored software is corrupted. GM sets P0601 in the engine module after one failed pass (or five once the first pass is complete) and turns on the lamp in the first trip; in body modules after two trips. Ford reports the same check as P0605, while GM, VW and Mazda use P0601. Typical causes are an interrupted reflash and manufacturer software errors – VW (2.0 TFSI) and Mazda (MX-5 2013) fixed it by reprogramming. The code alone does not say which module set it – the scan tool shows whether it is the engine, transmission, brake or body module.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Check engine light on
• Often no change in driving
• Possibly no start or limp mode if the software is badly damaged
• Transmission limp mode if the transmission module is affected

Common causes

• High Interrupted or faulty reprogramming
• Medium Faulty module software (update available)
• Medium Defective flash memory in the module
• Low Low voltage, voltage dips or a poor ground or supply at the module

Likelihood is a general estimate across vehicles; your make and model may differ.