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Code P0601. Internal Control Module Memory Checksum Error

The P0601 code is defined as an internal control module memory checksum error. This refers to a failure in the PCM’s internal control memory.

Although it is a generic code applicable to any brand of car, there are slight differences in terms of the concept of the fault. For example, for some brands, this code is activated after a certain number of communication failures, while for others it is activated at the first failure.

CAN System Operation

The P0601 code is directly related to the P060X family of codes, which include P0602, P0603, P0604, and P0605. It is set when the transmission control module (PCM) detects a communication failure between it and the auxiliary control modules.

When a communication failure occurs in any area of ​​the CAN system, the code will be stored and the warning light will turn on. Depending on the vehicle, it may take several driving cycles before the code is stored and the warning light illuminates.

The CAN controller network includes control modules for all vehicle systems. The actual number of control modules that make up the CAN system varies by manufacturer and model.

The CAN system controls all aspects of the vehicle’s operation. The vehicle’s microprocessors and controllers constantly exchange messages and signals between themselves and the sensors they control.

This is achieved through the intricate interconnection of wiring harnesses to create a “Signal Distribution”. Through this distribution, input and signal voltages are transmitted to various sensors, components, systems, and other controllers.

Signals go to and from the PCM. Basically, the P0601 error means that there is an internal fault in the powertrain control module (PCM).

You may also be interested in Error Code P0600 OBD – Serial Communication Link

What is Code P0601?

Fault code P0601 is called “Internal control module memory checksum error“, in different programs it can be called differently, although with the same context.

This fault designation applies to all OBD-II-equipped vehicles. It means that it is a generic code.

Error code P0601 is set when a memory checksum error is detected in the internal control module. This error is within the PCM (Powertrain Control Module), and is found when the PCM performs a self-test.

This will cause the Check Engine light to come on and put the vehicle into a fail-safe mode to minimize potential damage to the vehicle. Safe mode will only be disabled after the issue is fixed.

Common Symptoms of Code P0601

Error code P0601 can be difficult to identify as it may not show any noticeable symptoms to the driver in some cases, except of course for the activation of the Check Engine light on the dashboard.

The engine usually runs well and the gauges work. However, for some cases with symptoms, these are usually:

  • The ABS and traction control lights are on.
  • The engine may not start if it stops.
  • Difficult driving, with a tendency to turn off.
  • Transmission operation may be affected.
  • The “Check Engine” control light on the control panel comes on.
  • Illuminated transmission light.
  • Floating revolutions and attempts to stall at idle.
  • Reduced engine power.
  • Higher fuel consumption.
  • Problems with a particular system, indicate a possible loss of communication in that area.

There may be no symptoms other than a stored fault code. The P0601 code indicates an internal fault in the powertrain control module (PCM). Depending on what the failure affects, the error can be severe or moderate.

Possible Causes of Code P0601

Error code P0601 It means that the PCM has gone bad, which can be caused by a short circuit within the PCM itself or if the PCM cables and connectors are disconnected while the battery is still connected.

The most common cause of this error code is a faulty or damaged PCM and low voltage to the PCM.

  • The powertrain control module (PCM) has failed.
  • Low battery voltage.
  • Open circuit or short circuit in the wiring harness.
  • Loose or damaged connectors.
  • A bad ground connection.
  • The CAN bus may be faulty and have a short-to-ground or cable break.

How to Diagnose Code P0601

Diagnosing this code should begin by connecting the vehicle’s DLC port to a scan tool and checking all codes present, as well as the preset history and pending code.

Next, you should take note of the freeze frame data for each code. With this information, you can discern the conditions, such as engine load, RPM, and coolant temperature that the vehicle had when the code was set.

Then clear the codes so you can test drive the car to confirm if the same problem occurs again and if the code resets.

If the code returns, you should perform a visual inspection and look for signs of damage to the circuits and wiring of the components involved, which, in this case, is the PCM.

If you haven’t found anything, and the fault still persists, it’s time to check your PCM with a multimeter. You should check if the input voltage is reaching the PCM, as well as if there is an output voltage.

If you have not been able to find the fault, it is surely the PCM itself that is damaged. In this case, you must take it to a specialized service, where a specific test is performed to check its software and its condition.

Every car and every brand has a different procedure for PCM testing. Depending on the results, you can decide if the fault can be repaired, or change the PCM completely.

If the complete change is made, you must keep in mind that the new PCM must be programmed from scratch. It is best to dump the program from your old PCM to the new one, if possible. Many times the failure does not allow this step to be carried out.

How to Repair Code P0601

Perform a thorough visual inspection of all wiring support points on the body. These points represent ground connections.

You will often find loose connections or even grounding straps dangling after unrelated repairs have been made.

If bad grounds have been found and repaired, clear all codes and rescan the system to see if any codes return.

In some cases, it may be necessary to reintegrate or even reprogram some controllers after a communication failure.

Please note that this inspection may require the removal of the dashboard, seats, carpets, and even trim panels to access all of the wiring harnesses.

If no wiring damage is found, the P0601 code remains despite following the steps above. One option may be to replace the entire electrical harness.

However, this is not guaranteed to solve the problem, as the problem may be related to the driver.

Hopefully, if the fault is in the wiring, you can easily make the repair. But the most common thing when this code appears is that the problem is directly the PCM.

So the most common solution is to repair and reprogram the PCM, or failing that, replace it with an OEM replacement. That is why it is very important that, at this point, you should leave it in the hands of experts.

In some cases, people report that the code returns again and again even after replacing the PCM. This is because while most shops can replace the PCM, not all can program it.

Obviously, you need to find a service that can reprogram your PCM.

Common Errors When Diagnosing Code P0601

Many times this error is activated, and the diagnosis is made to the PCM without first verifying the wiring or the battery voltage. If the supply voltage is low, the PCM will have internal problems and will not work properly.

This type of fault can be resolved by simply changing the battery or repairing the wiring without having to touch the PCM. Therefore, it is essential to carry out the diagnosis before deciding to change the component.

Is Code P0601 Serious?

The severity of error code P0601 mainly depends on its symptoms. Additionally, the vehicle should not be driven if it exhibits extreme handling failures or difficulty moving.

In any case, it is advisable to carry out the diagnosis and repair as soon as possible.

To close

You may also be interested in Error Code P0605 OBD – Error in the read-only memory (ROM) of the internal control module

To fix the P0601 code, the most common solution is to replace and reprogram the PCM. However, faulty wiring or a low battery should also be considered as a cause of this error.

If all ground connections are secure, perform a thorough visual inspection of all vehicle wiring. The important thing is that you do not change the PCM without first carrying out a thorough diagnosis of the system.

If you want to know other articles similar to Code P0601. Internal Control Module Memory Checksum Error you can visit the category Fault Codes.


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