P0601

What it means

P0601 is the generic code for an internal control module memory checksum error. When the module runs its self-tests, it calculates a checksum of the data stored in its memory and compares it with the expected value. A mismatch means the stored program or data may be corrupted, so the module logs the fault. Which module is affected, usually the engine control unit, depends on the vehicle.

Symptoms

• Engine warning light on
• Engine cranks but fails to start, or starts and stalls
• Engine running in a reduced-power or limp mode
• Rough running, misfires or poor throttle response
• Gearbox behaving oddly, such as harsh or stuck gears, on vehicles where the engine module also controls the gearbox
• Fault returns soon after being cleared

Possible causes

• Internal fault in the control module (corrupted or failing memory)likely
• Low or unstable supply voltage to the module, for example from a weak battery or poor chargingpossible
• Poor module power or earth connections, or corroded or loose connectorspossible
• Interrupted or failed software update or reprogrammingpossible
• Outdated or faulty calibration in the module where the manufacturer has issued a correctionpossible
• Water ingress or heat damage to the module or its circuit boardrare
• Voltage spike from a shorted output device or incorrect jump-startingrare

How to diagnose

1. Read all stored codes and freeze frame data, noting whether other module or low-voltage codes are present
2. Check the battery condition and charging voltage, and rectify any weakness before further diagnosis
3. Inspect the module connectors, wiring, fuses and earth points for corrosion, damage, water or looseness
4. Check the module's power and earth circuits for voltage drop under load
5. Check for previous reprogramming, software updates or module replacement that may have gone wrong
6. Look for manufacturer service information or bulletins on this code for the specific model and engine
7. Clear the code, road test and recheck to see if it returns immediately, which points to a permanent fault
8. If the code is persistent and the supply is sound, check whether the module can be reprogrammed or needs replacing, depending on the model

How to fix

• Repair or replace the battery or charging system if voltage is low or unstable
• Clean, repair or replace faulty connectors, wiring and earth connections
• Reflash the module with the latest correct software or calibration where an update or failed programming is the cause
• Repair any short circuit or faulty output device that damaged the module supply
• Replace the control module and have it coded or programmed to the vehicle as the model requires
• Dry out and repair the cause of water ingress, then replace the module if it has been damaged

Can I keep driving?

This code for other makes

• P0601AudiLack of proper voltage to the PCM, Defective PCM memory module, Defective PCM ground circuit(s), Defective PCM controlled output devices
• P0601DodgeInternal PCM Controller Failure

Nearby codes

• P0600GenericSerial Communication Link
• P0602GenericControl Module Programming Error