P0605 Code: Internal Control Module Read Only Memory (ROM) Error

The powertrain control module (PCM) is the computer in charge of overseeing both the engine and in some vehicles, the transmission. If the PCM fails its self-diagnosis, its diagnostics will log a P0605 code.

What Does the P0605 Code Mean?

The Diagnostic Trouble Code (DTC) P0605 indicates “Internal Control Module Read Only Memory (ROM) Error.”

The PCM keeps the software for its operating system on its Read Only Memory (ROM). If the ROM develops a problem, the software stored on it can get corrupted. Without the right software, the module may stop running reliably.

In addition to managing how the engine and transmission operate, the PCM runs diagnostic tests on various engine and transmission parts. When it finds something wrong with a part, it sets the appropriate DTC for the issue.

The PCM regularly checks its own performance by running calculations. If it doesn’t get the right response from its ROM, it will set the internal control module code P0605.

Read our quick note about the ROM for more background on codes like P0605.

Note: The definition of code P0605 may differ according to the vehicle manufacturer. Check the right repair manual or repair database for the exact code definition.

What are the Possible Causes of the P0605 Code?

• Powertrain control module issues such as:
  • Incorrect voltage
  • Grounded
• Faulty PCM ROM memory module
• Faulty PCM ground circuit(s)
• Faulty output devices controlled by the PCM

What are the Common Symptoms of the P0605 Code?

• Check engine light will illuminate
• The vehicle fails an emissions inspection
• ABS/Traction control light may illuminate
• Vehicle may not perform as expected, such as:
  • Transmission doesn’t shift properly
• Reduced fuel economy
• Possible performance problems
  • Engine dies when the vehicle comes to a stop
  • Issues that resemble misfires

How to Diagnose the P0605 Code

A DTC P0605 is a generic trouble code that may be logged in vehicles from different auto manufacturers. Vehicles can share apparently similar triggers and symptoms. However, the steps for diagnosis and repair can differ between various makes and models.

If you have doubts about your ability to run diagnostics on your vehicle, it’s a good idea to bring your ride to a licensed mechanic. Here are some videos that may give you an idea of what the process might involve:

How to Fix the P0605 Code

Usually, the shop manual will simply require ECM/PCM replacement for codes like P0605, but the new unit has to be flashed to match the vehicle. Take note that in most cases, this isn’t a DIY repair.

Attempting to fix a P0605 code may become a frustrating task if you don’t have the right tools and know-how to test the PCM. In most cases, it’s best to leave the job to professionals.

For DIYers with advanced technical knowledge and hands-on experience who prefer to test and replace their vehicle’s PCMs on their own, it will be helpful to rely on the appropriate repair manual or refer to an online repair database.

A Quick Note About Read Only Memory (ROM)

The PCM is, in reality, a computer and it has a limited ability to detect and report problems in the systems it controls as well as within its own circuitry. Computers have two basic types of memory, namely Read Only Memory (ROM) or Random Access Memory (RAM). ROM is non-volatile, meaning that it retains whatever is written there even if power is lost.

RAM is like the workbench, where information is stored and retrieved, and it can be written and erased on the fly as demanded while driving. Meanwhile, nothing is erased from the ROM unless there’s some kind of data corruption issue with the files stored there, and that’s what this code indicates.

Flashable ECM/PCMs are as old as OBD2. These have an EEPROM, which can be erased and rewritten when the computer is “flashed” with new programming. Usually the “flash” involves feeding 18 volts to the EEPROM, erasing its original programming, and then a replacement program is written in by the system doing the flashing. On some units, the ROM and the EEPROM are integrated, but on others they’re separate.

Get a New PCM to Fix a P0605 Code Online

Your vehicle’s PCM can have several hardware-related issues when the P0605 code is triggered. This means that simply fixing the PCM with a computer might not be sufficient. You might need to replace the component to fix this code and eliminate its symptoms. Don’t put up with hardware issues when you can get a replacement PCM here at CarParts.com.

Replacing broken PCMs can be costly, but you don’t have to pay exorbitant prices at the dealership since CarParts.com offers all its parts at competitive prices. You can trust our components because they’ve passed stringent quality control standards during manufacturing. Our user-friendly website also makes shopping for replacement parts easy, so you can order the one you need in just a few clicks.

Our available PCMs are ready to ship, so we can deliver straight to your doorstep in as fast as two business days! Shop for parts like PCMs here at CarParts.com now.