How to Erase P0655: Engine RPM Output Circuit Malfunction

Welcome to another DIY car repair guide! In this article, we will discuss the P0655 error code, specifically focusing on the Engine RPM Output Circuit Malfunction. If you’ve encountered this error code, don’t worry. We’ll provide you with step-by-step instructions on how to diagnose and fix this issue, saving you time and money on expensive repairs. So let’s dive in and get your car back on the road!

1. Introduction

The P0655 error code indicates an issue with the engine RPM output circuit. This code is typically stored in the Engine Control Module (ECM) when it detects a malfunction in the circuit responsible for providing RPM information. When this error code appears, it can affect the performance of your vehicle and potentially cause further complications if left unaddressed.

2. Understanding the P0655 Error Code

The P0655 error code specifically relates to the engine RPM output circuit. The ECM relies on accurate RPM data to make critical decisions regarding fuel injection timing, ignition timing, and other engine functions. When the ECM detects a malfunction in the RPM output circuit, it triggers the P0655 error code, alerting you to the issue.

3. Common Causes of P0655

Several factors can contribute to the P0655 error code. Understanding the common causes will help you narrow down the possible culprits and facilitate a more efficient diagnosis. Here are some common causes to consider:

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  • Faulty wiring or connectors: Damaged or corroded wiring connections can disrupt the RPM signal and trigger the P0655 error code.
  • Defective Engine Control Module (ECM): A malfunctioning ECM can fail to interpret the RPM signal correctly, resulting in the error code.
  • Voltage supply issues: Insufficient or unstable voltage supply to the ECM can cause disruptions in the RPM signal and lead to the P0655 error code.

4. Diagnostic Steps for P0655

Now that we have a basic understanding of the P0655 error code and its common causes, let’s explore the diagnostic steps to pinpoint the exact source of the problem.

Step 1: Check for Other Error Codes

Before focusing solely on the P0655 error code, it’s crucial to check for any additional error codes that may be present. Other codes can provide valuable insights and help identify potential underlying issues that contribute to the RPM output circuit malfunction.

Step 2: Inspect Wiring and Connectors

Begin by visually inspecting the wiring harness and connectors related to the RPM output circuit. Look for any signs of damage, such as frayed wires, loose connections, or corrosion. If any issues are found, repair or replace the affected wiring or connectors.

Step 3: Test the Engine Control Module (ECM)

To determine if the ECM is functioning correctly, you’ll need to perform a thorough diagnostic test. Use a diagnostic scanner or code reader to retrieve and analyze data from the ECM. This will help identify any faults or inconsistencies in the ECM’s RPM output circuit operation.

Step 4: Check the Voltage Supply

A stable and sufficient voltage supply is crucial for the ECM to interpret the RPM signal accurately. Use a multimeter to measure the voltage at various points in the circuit, including the battery, alternator, and ECM. If voltage irregularities are detected, address the underlying issues to ensure a reliable power supply.

5. Fixing P0655: DIY Solutions

Now that you have diagnosed the cause of the P0655 error code, let’s explore some DIY solutions to fix the issue.

Solution 1: Replace Faulty Wiring or Connectors

If you discovered damaged wiring or connectors during the diagnostic process, it’s essential to replace them. Obtain the appropriate replacement parts and carefully follow the manufacturer’s instructions to ensure a proper and secure connection.

Solution 2: Repair or Replace the ECM

In cases where the ECM is found to be faulty, you may need to repair or replace it. Depending on your skill level and comfort with electronics, you can attempt ECM repairs if the issue is minor. Otherwise, it’s advisable to consult a professional mechanic or an authorized service center for ECM replacement.

Solution 3: Verify and Correct Voltage Supply Issues

If voltage supply irregularities were identified, take the necessary steps to address them. This may involve repairing faulty wiring, replacing a malfunctioning alternator, or resolving any other electrical issues affecting the power supply to the ECM.

6. Tips for Preventing P0655

Prevention is always better than cure. To minimize the chances of encountering the P0655 error code in the future, consider the following tips:

  • Regular maintenance: Follow the manufacturer’s recommended maintenance schedule for your vehicle. This includes regular inspections of wiring harnesses, connectors, and other electrical components.
  • Protect electrical connections: Ensure wiring connections are properly insulated and protected from moisture, debris, and other potential sources of damage.
  • Avoid electrical overloads: Be cautious when adding aftermarket electrical accessories to your vehicle. Overloading the electrical system can lead to voltage irregularities and potential malfunctions.
  • Keep the battery in good condition: Regularly check the battery’s health and replace it if necessary. A weak or faulty battery can affect the stability of the voltage supply to the ECM.

7. Conclusion

In conclusion, the P0655 error code, indicating an Engine RPM Output Circuit Malfunction, can be resolved through a systematic diagnosis and appropriate DIY solutions. By following the diagnostic steps outlined in this guide and implementing the recommended fixes, you can address the issue and restore your vehicle’s performance. Remember to prioritize safety and consult a professional if you are uncertain or uncomfortable with any aspect of the repair process.


Q1: Can I use a generic code reader to retrieve the P0655 error code?

Yes, a generic code reader should be able to retrieve the P0655 error code. However, to gain more detailed information about the error and accurately diagnose the issue, it’s advisable to use a professional-grade diagnostic scanner or consult a mechanic.

Q2: Can a loose battery terminal cause the P0655 error code?

Yes, a loose or corroded battery terminal can potentially disrupt the voltage supply to the ECM and trigger the P0655 error code. Ensure the battery terminals are clean, securely connected, and free from corrosion.

Q3: Are there any risks involved in repairing the ECM myself?

Repairing the ECM requires advanced knowledge and expertise in electronics. If you are not confident in your abilities, it’s best to seek assistance from a professional mechanic or authorized service center to avoid further complications or damage to the vehicle’s electrical system.