P0605: Internal Control Module Read Only Memory Error

What is the engine computer reporting with P0605?

The computer found an error in the fixed programming memory that stores its core operating instructions, which is different from the learned values that a keep alive memory error covers.

The code sits in the engine computer program memory area and is reported by the comprehensive component monitor. It names the circuit or the condition where the computer saw a reading outside its expected range. It does not name a failed part, and several genuinely different faults set this same code, which is the whole reason the causes below are ordered rather than listed.

What people usually notice

• Engine runs poorly or in a limited mode
• Check engine light with significant drivability change
• Engine may not start
• Multiple unrelated codes stored at once

What is actually behind P0605?

The causes below are ordered by how often they turn out to be the answer, cheapest and most common first. That order matters more than the list itself: the expensive component named in the code text is very rarely the first thing to replace, and working down from the top is what stops a engine computer program memory fault becoming an expensive guess.

Internal computer hardware fault is the one to rule out before anything else. The most common cause of a read only memory error.

How do you diagnose P0605?

Start with freeze frame. There is no meaningful freeze frame for this fault. That snapshot is taken at the instant the code set, and it is the single most useful piece of evidence you have, which is also why clearing the code before reading it is such a costly habit.

Diagnosing this one properly means commanding a component and watching whether it responds, which a read-only tool cannot do at any price. Correcting this usually requires reprogramming or replacing the computer, which needs a capable scan tool.

The order worth working in

• 1. Internal computer hardware fault: The most common cause of a read only memory error.
• 2. Corrupted software from an incomplete update: An interrupted reflash can damage this memory.
• 3. Water intrusion into the computer: Moisture can damage the memory chip itself.
• 4. Corroded connector affecting a power or ground pin: A poor connection can occasionally trigger this fault.
• 5. Electrical surge damage: A jump start done incorrectly or a lightning strike nearby can damage internal memory.

Can you keep driving with P0605?

The engine may run in a limited or unpredictable mode since its core operating instructions may be corrupted, avoid a long trip until this is checked.

This is a severity 2 of 4 code. It will not usually strand you, but it will fail an emissions test while it is present, and the underlying fault rarely gets cheaper by being left alone.

What does it cost to ignore P0605?

A corrupted core program can leave the engine running poorly or not at all, this is not something that improves with time.

There is also the diagnostic cost of waiting. Freeze frame data, pending code history and the readiness monitor state all describe the fault as it was when it set, and all of it is lost the moment somebody clears the code to make the lamp go out.