How to Fix P0606: Internal Control Module Read Only Memory (ROM) Error

As a car owner, encountering error codes can be quite frustrating, especially when they disrupt the smooth functioning of your vehicle.

One such error code is P0606, which indicates an issue with the internal control module’s read-only memory (ROM).

In this article, we will explore the causes of the P0606 error, diagnostic steps to identify it, and provide you with a step-by-step guide on how to fix it yourself.

Understanding the P0606 Error

The P0606 error is triggered when the vehicle’s internal control module detects a malfunction in its read-only memory.

car vertical

The read-only memory contains essential data and instructions that help the module perform its functions. The most common causes of the P0606 error include a faulty module, damaged wiring or connectors, or a software issue within the module itself.

Symptoms of the P0606 error may include the illumination of the Check Engine Light (CEL), poor engine performance, difficulty starting the vehicle, or even a complete engine failure. If you experience any of these symptoms, it is important to address the issue promptly.

Diagnostic Steps

To diagnose the P0606 error, follow these steps:

Step 1: Perform a visual inspection of the vehicle’s wiring and connectors.

Check for any visible damage, loose connections, or corrosion. Ensure that all connections are secure and in good condition.

Step 2: Use a diagnostic scanner to retrieve the trouble codes.

Connect a diagnostic scanner to your vehicle’s onboard diagnostic (OBD) port and retrieve the trouble codes. The P0606 error code should be among the codes displayed.

Step 3: Analyze the retrieved codes and identify the P0606 error.

Examine the trouble codes shown on the scanner and identify the P0606 error specifically. This will help you narrow down the problem area.

Resetting the Error Code

Once you have identified the P0606 error, you can attempt to clear the error code by following these steps:

Step 1: Disconnect the vehicle’s battery to clear the error code.

Locate the vehicle’s battery and disconnect the negative terminal. This will prevent any electrical current from flowing through the system.

Step 2: Wait for a few minutes before reconnecting the battery.

Allow the vehicle to sit for approximately 5-10 minutes to ensure that any residual power is drained from the system.

Step 3: Reconnect the battery and start the vehicle to check if the error code is cleared.

Reconnect the negative terminal of the battery and start the vehicle. If the error code was successfully cleared, the Check Engine Light should no longer be illuminated.

Checking the Internal Control Module

If the error code persists after resetting, it is necessary to inspect the internal control module itself:

Step 1: Locate the internal control module in the vehicle.

Refer to your vehicle’s manual to find the location of the internal control module. It is usually found under the dashboard or inside the engine compartment.

Step 2: Inspect the module for any physical damage or signs of corrosion.

Carefully examine the module for any visible signs of damage, such as burnt or corroded pins, loose connections, or water intrusion. If any damage is found, it may indicate a need for replacement.

Step 3: Use a multimeter to test the voltage and continuity of the module’s circuits.

Using a multimeter set to the appropriate settings, test the voltage and continuity of the module’s circuits. Compare the readings to the specifications provided by the vehicle manufacturer. Deviations from the expected values may indicate a faulty module.

Repairing the Internal Control Module

Based on the inspection results, you can proceed with the appropriate repair actions:

Step 1: If any physical damage is found, consider replacing the module.

If you have identified physical damage to the internal control module, it is advisable to replace it with a new or refurbished one. Consult with a trusted automotive parts supplier or a professional mechanic for the exact replacement part.

Step 2: If no physical damage is found, try reprogramming the module.

In cases where there is no visible damage, attempting to reprogram the module’s software might resolve the issue. However, reprogramming should be performed by a professional using specialized equipment and software.

Step 3: Seek professional assistance if reprogramming is unsuccessful.

If reprogramming the module does not resolve the P0606 error, it is recommended to seek the assistance of a qualified automotive technician. They have the expertise and diagnostic tools to further diagnose and repair the issue.

Preventing Future P0606 Errors

To minimize the likelihood of encountering the P0606 error or similar issues in the future, consider the following preventive measures:

  • Follow the manufacturer’s recommended maintenance schedule for your vehicle.
  • Regularly inspect and clean the internal control module’s connectors to prevent corrosion.
  • Use high-quality components and avoid using aftermarket modules or software that may not be compatible.
  • Avoid electrical overloads or voltage spikes by ensuring a stable electrical system in your vehicle.


The P0606 error can be a concerning issue for any car owner, but with the right knowledge and guidance, you can tackle it effectively. In this article, we discussed the causes, diagnostic steps, and repair methods for the P0606 error related to the internal control module’s read-only memory. By following the outlined steps and considering preventive measures, you can resolve the issue and maintain the optimal performance of your vehicle.


What other error codes are commonly associated with the P0606 error?

  1. Other error codes that are often associated with the P0606 error include P0600 (Serial Communication Link Malfunction) and P0601 (Internal Control Module Memory Check Sum Error). It is important to diagnose and address these codes promptly to ensure the proper functioning of your vehicle.

Can I fix the P0606 error myself, or do I need professional help?

  1. While some steps, such as resetting the error code, can be performed by car owners with basic knowledge, diagnosing and repairing the internal control module may require professional expertise and specialized equipment. It is recommended to consult a qualified mechanic or technician for accurate diagnosis and repair.

How much does it typically cost to replace an internal control module?

  1. The cost of replacing an internal control module can vary depending on several factors, including the make and model of your vehicle, the supplier or dealership you choose, and whether you opt for a new or refurbished module. Generally, the cost can range from $200 to $800 or more. It is advisable to obtain quotes from different sources to get a better idea of the specific cost for your vehicle.