P0601: Internal Control Module Memory Check Sum Error
The engine computer ran a self test of its own memory and the result did not add up, which can mean corrupted software or a failing module.
What P0601 means
The engine computer runs regular self tests. RepairPal explains that P0601 means the memory check sum test is failing. A check sum is a calculation over the stored software; if the result does not match the expected value, the computer knows its memory may be corrupted. That memory holds the operating software and calibration that control fuel, spark and often the transmission, so a fault here can affect almost anything, from a no start to poor running and odd shifting. KBB recommends avoiding driving because problems can spread across the car. Causes include corrupted software from a failed update, a failing memory chip, water damage and supply voltage problems. Before replacing an expensive module, shops check battery voltage, power feeds and grounds at the computer, look for software updates or service bulletins, and try reprogramming the module. If the code returns after a successful reflash, the computer is replaced and programmed to the vehicle.
Common symptoms
- Check engine light on
- Engine may not start
- Stalling or poor running
- Shifting problems
- Multiple warning lights
Most common causes
- Corrupted engine computer software
- Failed engine computer memory
- Interrupted or failed reprogramming
- Low voltage or poor ground at the computer
- Water damage to the computer
What to check yourself first
Make sure the battery is fully charged and terminals are clean, since low voltage can upset computer self tests. Ask a dealer or shop whether a software update exists for your car. Do not try to reprogram the computer yourself without proper tools and a battery support charger.
Typical fixes and what they cost
| Fix | Typical cost | Note |
|---|---|---|
| Powertrain control system diagnosis | $61-$90 | Checks power, grounds and software level before replacing the computer. |
| Replace engine control module (ECM/PCM) | $1,122-$1,192 | If reprogramming fails or the internal fault returns. |
| Replace battery | $456-$493 | If a weak battery caused low voltage during start up or programming. |
Typical US price ranges for parts and labor, not quotes. Your shop should confirm the cause with a diagnostic before replacing parts.
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Related codes
- P0603 Internal Control Module Keep Alive Memory (KAM) Error
- P0604 Internal Control Module Random Access Memory (RAM) Error
- P0606 Control Module Processor
- P0562 System Voltage Low
- U0100 Lost Communication With ECM/PCM "A"