How to Fix Code P0601: Serial Communication Link Malfunction

If you’re experiencing trouble with your car and have encountered a diagnostic trouble code (DTC) P0601 – “Serial Communication Link Malfunction,” it can be quite frustrating.

This code indicates a problem with the communication link between the powertrain control module (PCM) and other modules in your vehicle.

In this article, we will explore what Code P0601 is, its symptoms, causes, and most importantly, how to fix it yourself.

What is Code P0601?

Code P0601 refers to a malfunction in the serial communication link between the PCM and the other modules in your vehicle.

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The PCM acts as the central computer that controls various systems, such as the engine, transmission, and emissions.

When the communication link is disrupted, it can lead to a range of issues.

Symptoms of Code P0601

Identifying the symptoms associated with Code P0601 can help you diagnose the problem accurately. Some common symptoms of this code include:

  1. Check Engine Light: The most obvious sign is the illumination of the check engine light on your vehicle’s dashboard.
  2. Engine Performance Issues: You may experience poor acceleration, rough idling, or even stalling.
  3. Transmission Problems: Shift points may become erratic, and the transmission may not operate smoothly.
  4. Electrical Malfunctions: Other electrical systems, such as power windows, central locking, or climate control, may exhibit unusual behavior.

Causes of Code P0601

Several factors can contribute to the occurrence of Code P0601:

  1. Faulty PCM: The PCM itself may be defective, causing communication errors.
  2. Battery or Charging System Issues: Low battery voltage or irregular charging can disrupt communication.
  3. Wiring Problems: Damaged or loose wiring connections between modules can interfere with communication.
  4. Software Issues: Outdated or corrupted software in the PCM or other modules can lead to communication failures.

Diagnosing Code P0601

Before proceeding with the fix, it’s crucial to diagnose the problem correctly. Follow these steps to pinpoint the cause of Code P0601:

Step 1: Check for other codes

Start by using an OBD-II scanner to check if there are any other codes present. Addressing any additional codes will ensure a more accurate diagnosis.

Step 2: Check the battery

Inspect the battery for signs of corrosion, loose connections, or low voltage. Ensure that the battery terminals are clean and tight. If the battery is old or weak, consider replacing it.

Step 3: Inspect the wiring

Carefully examine the wiring harnesses connected to the PCM and other modules. Look for any signs of damage, frayed wires, or loose connectors. Repair or replace any faulty wiring as necessary.

Step 4: Check the PCM

To determine if the PCM is the culprit, you may need to perform further tests or seek professional assistance. A specialized automotive technician can perform diagnostic procedures using advanced tools.

Step 5: Perform a software update

If you’ve ruled out other causes and suspect a software issue, consider updating the software in your PCM and other affected modules. Check with your vehicle manufacturer’s website or consult a professional to ensure you have the correct software update.

Fixing Code P0601

Once you have diagnosed the problem and identified the cause, it’s time to fix Code P0601. Here are the steps you can take:

Step 1: Clear the code

Using an OBD-II scanner, clear the code from the PCM’s memory after addressing the underlying issue. This will reset the check engine light. However, if the problem persists, the code will reappear.

Step 2: Replace the PCM

If all other potential causes have been eliminated, and the PCM is deemed faulty, you may need to replace it. Consult your vehicle’s service manual or seek professional help for guidance on PCM replacement.

Step 3: Perform a software update

After replacing the PCM, it’s essential to update the software to the latest version. Follow the manufacturer’s instructions or consult a professional to ensure a successful software update.


Code P0601, indicating a serial communication link malfunction, can be troublesome for car owners. However, by following the diagnostic steps and addressing the underlying causes, you can resolve this issue and restore your vehicle’s performance. If you’re uncomfortable with performing these steps yourself, it’s always recommended to consult a professional automotive technician for assistance.


Can I continue driving my car with Code P0601?

  1. It is generally not advisable to drive with Code P0601. The underlying communication issues can affect critical systems in your vehicle, potentially leading to further damage or safety concerns. It’s best to address the problem promptly.

Do I need specialized tools to diagnose Code P0601?

  1. While an OBD-II scanner is essential for reading and clearing codes, diagnosing the specific cause of Code P0601 may require more advanced tools and expertise. Professional automotive technicians have access to specialized equipment to accurately diagnose and repair the issue.

Can a software update fix Code P0601?

  1. In some cases, a software update can resolve Code P0601, especially if the problem stems from outdated or corrupted software. However, it’s crucial to ensure that the correct software update is applied, as an incorrect update can cause further issues. Consult your vehicle manufacturer or a professional for guidance.