Computer & output circuits · Powertrain · generic (SAE-defined)
P0601: Internal Control Module Memory Check Sum Error
P0601 means the engine computer's self-test found that the data stored in its permanent memory does not match the checksum it expects, suggesting corrupted programming.
Standard title per SAE J2012 / ISO 15031-6 · Updated 2026-11-07 · By CarWhere Research
How P0601 sets
The engine control module (ECM) or powertrain control module (PCM) periodically adds up the contents of its program memory and compares the result with a stored checksum value. If the two do not agree, the module assumes its software or calibration is corrupted and sets P0601. This self-test runs internally; there is no external sensor involved.
Common causes of P0601
Roughly most likely first; the actual cause depends on the vehicle and needs testing to confirm.
- Interrupted or failed PCM programming (reflash) session
- Internal memory failure in the PCM
- Voltage spike or low-voltage event during operation or jump-starting
- Water intrusion or corrosion inside the module
- Poor PCM power or ground connections
P0601 symptoms
- Check engine light on
- Engine may not start or may stall
- Rough running or reduced power
- Erratic transmission shifting on vehicles with an integrated PCM
- Sometimes no noticeable symptoms other than the light
How P0601 is diagnosed
- Record freeze frame data and all stored codes, including other internal module codes
- Ask whether the module was recently reprogrammed, replaced or the vehicle jump-started
- Verify battery condition and PCM power and ground circuits
- Clear the code and see whether it returns immediately on the next key cycle
- Check for a software update or service bulletin that addresses the code
- Attempt a reprogram with the correct calibration before replacing the module
Typical fixes for P0601
- Reprogram the PCM with the correct, current calibration
- Repair PCM power or ground faults, then recheck
- Replace the PCM and program it to the vehicle, including immobilizer setup where required
Replace parts only after testing confirms the cause — a code names the circuit or condition that failed a check, not necessarily the faulty part. We don’t publish per-repair prices; for what households actually spend on upkeep, see car repair costs.
Related codes & warning lights
P0601 FAQ
What does code P0601 mean?
P0601 means the engine computer's self-test found that the data stored in its permanent memory does not match the checksum it expects, suggesting corrupted programming. The standard definition is "Internal Control Module Memory Check Sum Error."
Can I drive with a P0601 code?
It is not recommended. Corrupted programming can cause stalling, no-start or unpredictable engine behavior, so limit driving and have the module checked as soon as possible.
Can a reflash fix P0601?
Often it can, especially if a previous programming session was interrupted. If the code returns right after a correct reflash, the memory hardware itself has likely failed.
Will a used computer work as a replacement?
A used module usually has to be programmed with the vehicle's VIN and immobilizer data before it will run the engine, so plan for programming either way.
Keep researching
More computer & output circuits codes
Sources
- SAE J2012 — Diagnostic Trouble Code Definitions (standard code titles)
- ISO 15031-6 — Road vehicles: communication between vehicle and external equipment for emissions-related diagnostics, Part 6: Diagnostic trouble code definitions
- U.S. EPA — Vehicle Emissions Inspection and Maintenance (I/M) programs
- U.S. EPA, 40 CFR 86.1806-17 — Federal onboard diagnostics requirements for light-duty vehicles
General information written by CarWhere Research, not a diagnosis of your vehicle. Manufacturers can add their own sub-definitions and test conditions; confirm with the factory service information for your year, make and model. Before paying for a repair, check NHTSA for open recalls and your warranty booklet: federal law requires an emissions warranty on major emission-control parts such as the catalytic converter and engine computer.