The P0605 code in your 2022 Toyota RAV4 indicates that the ECM has detected an error in its read only memory (ROM). ROM stores the fundamental programming that tells the ECM how to operate—the firmware that never changes under normal circumstances. When ROM verification fails, the ECM cannot trust its own programming instructions.
ROM vs. Other Memory Types
Your RAV4's ECM contains several memory types with different functions. ROM holds permanent programming like calibration tables, operating algorithms, and basic functionality code. Unlike RAM or keep alive memory, ROM shouldn't change during normal operation. A ROM error suggests either corruption of this critical data or hardware failure in the memory chips themselves.
Causes of ROM Errors
Failed or interrupted software updates are the most common cause in newer vehicles like your RAV4. If power is lost during an ECU update, ROM can be left in a partially written state. Severe voltage spikes can damage ROM cells. Physical damage from water intrusion, extreme heat, or vibration affects the memory chips. Manufacturing defects occasionally cause premature ROM failure.
Symptoms in Your RAV4
With P0605 active, your RAV4 may not start at all, as the ECM cannot verify its basic programming. If it does start, severe drivability issues including rough running, stalling, and limp mode are common. The vehicle may behave erratically as the ECM attempts to execute corrupted instructions.
Diagnosis and Repair
Using Toyota Techstream, check if the ECM can communicate and what software version is installed. Attempt a reflash with the correct calibration for your VIN. If reprogramming fails or the code returns immediately, the ECM requires replacement. Given your RAV4 is still under warranty, Toyota should cover ECM replacement for manufacturing-related ROM failures.