Internal Control Module Memory Check Sum Error
The Powertrain Control Module (PCM) continuously runs self-diagnostic tests on its internal memory to ensure data integrity. Code P0601 is set when the PCM calculates a memory checksum that does not match the expected value, indicating a failure within the module's internal ROM or EEPROM.
A memory checksum error means the engine computer is failing internally. This can lead to unpredictable vehicle behavior, stalling, or a complete no-start condition, making it unsafe to drive.
Common symptoms
- Illuminated Check Engine Light (MIL)
- Engine cranks but fails to start
- Engine stalling or shutting off unexpectedly while driving
- Erratic shifting or transmission control issues
- Unpredictable engine performance or rough idling
Likely causes
- Internal failure of the Powertrain Control Module (PCM)
- Corrupted PCM software or failed programming/flashing event
- Poor power or ground connections to the PCM causing memory corruption
- Voltage spikes from a failing alternator or improper jump-starting
- Water intrusion or physical damage to the PCM
What to check before replacing parts
Check battery voltage and charging system health.
Look for: Ensure the battery rests at 12.4-12.6V and the alternator outputs 13.5-14.5V without excessive AC ripple, as voltage issues can cause module errors.
Inspect the PCM wiring harness and connectors.
Look for: Look for corrosion, bent pins, or signs of water intrusion at the PCM connectors that could cause poor power or ground delivery.
Perform a voltage drop test on PCM power and ground circuits.
Look for: A voltage drop of more than 0.1V on ground circuits or 0.2V on power circuits indicates high resistance that must be repaired.
Check for Technical Service Bulletins (TSBs) regarding PCM software updates.
Look for: Determine if the manufacturer has released a software update or reflash procedure specifically addressing the P0601 code for your vehicle.
Clear the code and perform a hard reset of the PCM.
Look for: Disconnect the battery for 15 minutes, reconnect, and test drive; if P0601 returns immediately, the PCM has suffered a permanent internal failure and likely requires replacement.
This page explains the generic P0601 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
Gear guide: Best OBD2 ScannersRead this code yourself next time — from $20 Bluetooth dongles to bidirectional scan tools.Rather have a pro handle it? Find a vetted local mechanic.