P0601: Internal Control Module Memory Check Sum Error (Meaning, Causes, Fixes)
What P0601 means
The powertrain control module (PCM) is the computer that runs the fuel, ignition and, on many vehicles, transmission systems. RepairPal explains that the PCM regularly runs self-tests, and one of them is a check sum test of its memory, which stores the PCM's operating software and its short-term calculations. If the result isn't what the PCM expects, it sets P0601. OBD-Codes.com describes it simply as an internal fault in the PCM and notes many reported PCM failures on Chrysler and Dodge vehicles, where the code means a serial communication inside the computer failed at least 6 times, although it can happen on any vehicle. The code is generic to OBD-II vehicles, but repair steps vary by make and model. Search interest shows people look it up most for Chevrolet (including the Silverado and Malibu), Dodge (including the Ram 1500) and Hyundai, so check technical service bulletins (TSBs) for your vehicle.
Severity: can I keep driving?
Stop and fix promptly
Get it checked soon. RepairPal rates P0601 'Urgent', meaning it can cause severe damage, because the engine computer can't be trusted to run the engine and transmission correctly when its memory fails a self-test. OBD-Codes.com says that in many cases the engine runs fine and the only sign is the check engine light, so the sources disagree on how bad it feels from the driver's seat. If the engine stalls, misfires or the transmission shifts badly, stop driving and have it towed. Don't unplug the engine computer with the battery still connected; OBD-Codes.com says that alone can set this code.
Common symptoms
- Check engine light on
- Often no other symptoms; OBD-Codes.com says the engine typically runs fine and the gauges work
- ABS or traction control light may come on (RepairPal)
- Vehicle may not run or shift properly, and in some cases may die when coming to a stop or act like it is misfiring (RepairPal)
- Readiness monitors reset to 'not ready' every time the key is turned off, which can fail an emissions inspection (RepairPal)
- Lower fuel economy (RepairPal)
Likely causes
Roughly most to least common, based on the sources below. Your vehicle may differ.
- A failed engine computer (PCM), for example from an internal short (OBD-Codes.com says this is the cause in most cases)
- Poor or inconsistent 12-volt power supply to the PCM (RepairPal)
- Bad PCM ground circuit or circuits (RepairPal)
- A shorted output device controlled by the PCM, which can damage its memory (RepairPal)
- Unplugging the PCM connector while the battery is still connected (OBD-Codes.com)
Diagnostic steps you can do
Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.
- Read all stored codes and freeze frame data and write them down.
- Check the battery and charging system, and make sure the battery terminals are clean and tight, since RepairPal says low or unsteady voltage to the PCM is a common root cause.
- Look for loose, corroded or damaged engine and PCM ground connections.
- Look up technical service bulletins and software updates for your year, make and model.
- Check your warranty: OBD-Codes.com says a PCM replacement may be covered under the emissions warranty even if your other warranties have run out.
- Clear the code and drive. OBD-Codes.com notes that many owners report it coming right back, which points to the PCM itself.
Typical fixes
- Repair the PCM power supply or ground circuits if they test bad
- Find and repair any shorted PCM-controlled output device before installing a new PCM
- Reflash (reprogram) the PCM, which OBD-Codes.com says works in a few cases
- Replace and reprogram the PCM, which OBD-Codes.com calls the most common fix
Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.
🛠 When to call a pro
- RepairPal's diagnostic theory: in many cases the PCM is not getting a good, steady 12-volt supply. Verify PCM power and ground circuits under load before condemning the PCM.
- RepairPal lists replacing the PCM when the real cause is bad voltage or bad grounds as a common misdiagnosis, and says to check for shorted output devices first so a new PCM isn't damaged too.
- A replacement PCM normally has to be programmed to the vehicle. OBD-Codes.com recommends a dealer for this and notes that not every shop that can swap a PCM can program it.
- The sources disagree on the likely cause: OBD-Codes.com says P0601 in most cases means the PCM has gone bad, while RepairPal puts power and ground problems first. They also differ on severity, with RepairPal rating it 'Urgent' and OBD-Codes.com saying there are usually no symptoms beyond the light.
Where to buy
Plain search links. Always match parts to your exact year, make, model and engine.
FAQs
Can I drive with P0601?
Carefully, and only for a short time. OBD-Codes.com says the engine often runs fine, but RepairPal rates P0601 'Urgent' because a computer with failing memory may not run the engine or transmission properly. If the engine stalls, misfires or shifts badly, stop driving it.
Does P0601 always mean a bad PCM?
Not always. OBD-Codes.com says it usually does, but RepairPal says poor power or ground to the PCM is a common cause and that replacing the PCM without checking those is a common misdiagnosis.
Is a PCM replacement for P0601 covered by warranty?
It may be. OBD-Codes.com says it may be covered under the emissions warranty even after the bumper-to-bumper and powertrain warranties end, so check your warranty guide or ask a dealer.
What codes are related to P0601?
OBD-Codes.com lists the other internal control module codes P0602 through P0605, and the PCM code range P0600 to P0610 includes P0606 (processor fault) and P0607 (performance).
Sources
Last reviewed 2026-10-26. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.