How to Fix P0605 Code: Resolving the “Internal Control Module ROM Error”

OBD2 Scanners is reader-supported. When you buy through links on our site, we may earn an affiliate commission.

computer screen with  p0605 on the screen

What do you do if you are driving and your Check Engine Light comes on, along with diagnostic trouble code P0605? Most people would take their car to a mechanic to check it out.

But, did you know that you can fix it yourself? Yes, you read it right! By reading this guide, you can save time and money by fixing the P0605 code yourself. Sounds amazing, right? So what is this trouble code, and how to fix it? Read on!

What is Code P0605?

The P0605 code is a generic powertrain code for "Internal Control Module Read Only Memory Error." This code is triggered when the Powertrain Control Module (PCM) or the Engine Control Module (ECM) detects an error in the program stored in its read-only memory.

Read-only memory (ROM) is a memory made up of data that the engine control module (ECM) places in a processor and can't be erased by any means. The data includes ECM tests and numeric ranges, which are all critical for various sensors such as interior buttons, oxygen sensors, Mass Air Flow (MAF) sensors to run correctly.

If the PCM detects that the values stored in the processor don't match the vehicle manufacturer's parameters, it will trigger a P0605 trouble code. 

Symptoms of Code P0605

When the P0605 code is triggered, there is a high chance that the memory stored in the ECM is lost or disturbed. In these cases, you may experience these symptoms:

  • Check Engine Light is On
  • Poor fuel economy
  • Engine misfiring
  • Engine stalling
  • Engine not starting
  • A decrease in performance

Causes of Code P0605

When your car's Check Engine Light illuminates, there are many things you may blame, such as a faulty oxygen sensor or spark plug. However, when the P0605 code is shown, it's usually because of one of these problems:

  • A failed or damaged ECM
  • Dirty and corroded components
  • Wrong ECM programming process or using an aftermarket performance programmer
  • Defective power supply
  • Deleted memory stored in the ECM
  • Vacuum Leak

How to Diagnose Error Code P0605?

If you notice the causes mentioned above, you may think this issue is more challenging to diagnose. However, this guide will outline specific steps you can take to help make the process a little less daunting.

Are you ready to start diagnosing? Hold off! Are you mechanically inclined? If so, great! Remember that diagnosing requires automobile knowledge as it may cause further damage to your car if done incorrectly. If you are confident enough, then let's start!

Check for Other Trouble Codes

Before anything else, make sure to check for other diagnostic codes. Plug your OBD scanner into your car's diagnostic port. Turn the engine on and wait for the scanner to read the codes. If you have more than one code, start with the P0605 code, which is likely related to the others.

Clear The Code

If you only have the P0605 trouble code, clear it by unplugging your scanner and restarting your car. Once the code is cleared, drive your car for a few miles and see if the check engine light comes back on. If it does, then you'll need to continue diagnosing the issue.

Perform Visual Inspection

Another important step when diagnosing this issue is doing a visual inspection. Inspect all the electrical terminals and connectors and ensure they are securely connected. It is best to disconnect the connectors and reconnect them again to provide a fresh and clean electrical connection. 

Furthermore, check the wires connecting the ECM and MAF. Ensure that no high voltage sources are near the MAF or its wiring. 

Check for Vacuum Leaks

If you've checked out all the electrical components and still can't find the root of the problem, then it's time to check for vacuum leaks. Start your engine and spray soapy water around vacuum hoses and fittings. If there are any leaks, you'll see bubbles form. Replace the hoses if necessary.

How to Fix Code P0605?

If doing all the steps above did not fix the issue, there is a high chance that your mass airflow sensor is the one causing the problem. In this case, you may need to replace it. Make sure to get one suitable for your car's make and model. 

You can find a mass airflow sensor at most auto parts stores or order one online. Once you have the new sensor, follow these steps to replace it:

  1. Locate the mass airflow sensor. It's usually located on or near the air filter box.
  2. Disconnect the MAF sensor's electrical connector.
  3. Remove the mounting screws and remove the sensor.
  4. Install the new MAF sensor and reconnect its electrical connector.
  5. Replace the mounting screws and tighten them.
  6. Reconnect the negative battery cable.

If you have followed these steps correctly, your car should now be running without any trouble codes! Remember to always consult your vehicle's service manual for specific instructions on how to repair your vehicle. As always, if you are not comfortable performing these repairs yourself, take your car to a qualified mechanic.

Common Mistakes When Diagnosing the Code P0605

Many people diagnose and repair their car issues without enough automotive knowledge and skills. This might work out sometimes, but it will only lead to more car problems most of the time. If you want to avoid making mistakes when diagnosing the code P0605, here are some of the common mistakes you should avoid:

  • Fixing the problem without having the right tools and equipment.
  • Repairing the issue without knowing what is causing the problem in the first place.
  • Neglecting other codes that might be present along with the code P0605.
  • Replacing the mass airflow sensor without checking for damaged electrical connectors.

Code P0605 FAQs

1. How serious is the P0605 code?

The P0605 code is considered a serious error code. If the problem is not fixed, it can lead to drivability problems and even engine misfire.

2. Can I drive with my check engine light illuminated due to this fault code?

No, you should not drive your vehicle with the check engine light illuminated. Driving with a malfunctioning sensor can lead to more severe problems down the line.

3. What special tools can I use to pinpoint the exact issue of the P06065 code?

You can use a scan tool to read the error code and help you pinpoint what is causing the problem. You can also use a multimeter to test the sensor for continuity.

4. Will the P0605 code comes back after I fix it?

The code may come back after you have repaired it. It is essential to follow the repair instructions closely and to test the sensor after completing the repair.

5. Can I fix the code P0605 myself?

Yes, you can repair this issue yourself; however, you should ensure you have the proper tools and enough skills.


So there you have it – a guide on fixing the P0605 code yourself. The code P0605 is not as hard to diagnose and fix as you may believe. It may be considered a serious issue, but with the help of this guide, you will be able to repair it in no time.

So, how did this guide work for you? Were you able to successfully clear the code and get your car back up and running? We hope so! If not, don't worry – you can ask in the comment section so we can try to help you out. Thanks for reading, and happy driving!