When your car shows the P0605 engine code, it means there’s a problem with your Engine Control Module’s (ECM) Read-Only Memory (ROM). This could make it difficult to start your engine, and it might even decrease your fuel efficiency.

Diagnostic trouble codes (DTCs) can help you find out what’s wrong with your car. But they can only tell you where to look. It’s important to understand the potential causes and symptoms of each code to properly diagnose and fix the issue.

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What does the engine code P0605 mean?

Definition: Engine code P0605 means that there’s a problem with your ECM’s ROM.

Your car’s ECM facilitates nearly everything—from the fuel and ignition systems to the transmission and traction control systems. Problems in your ECM’s memory can lead to issues in fuel efficiency, gear shifting, and handling. Given its role in fuel management, a P0605 engine code could also cause you to fail emissions tests.

MORE:

How to pass emissions testing

How much will it cost to fix?

Diagnosing the issue in a P0605 engine code typically takes around an hour, which should cost somewhere around $75 to $100 depending on your auto shop’s rates. Since you shouldn’t need to replace any parts to repair this error code, the only additional costs should be labor charges for your mechanic's time.

What can cause the P0605 engine code?

While a P0605 engine code could be related to larger problems in your engine, it’s typically caused by a lack of voltage to the Powertrain Control Module (PCM). As a result, this issue usually arises in situations where your

battery dies

or is disconnected.

Although less common, engine code P0605 could also result from the following:

Defective PCM ROM memory module

Defective PCM ground circuit(s)

Defective PCM controlled output devices

MORE: How to understand car OBD codes

Common symptoms of the P0605 engine code

Since the ECM is connected to so many systems in your car, you’ll likely see a variety of symptoms when it fails. Here are some of the most common signs of a P0605 engine code:

Check engine light turns on

Failed emissions inspection test

Antilock braking system warning light turns on

Problems shifting gears

Lower fuel efficiency

In some rare situations, your engine may even misfire or shut off at a stop as a result of engine code P0605.

How serious is the P0605 engine code?

Engine code P0605 often causes problems that impact your ability to drive. As a result, the code is very serious and could endanger you on the road.

It’s best to have a professional diagnose and repair the issue as soon as possible to avoid any potential problems. Additionally, failing to address a P0605 engine code could cause you to fail your emissions test, which could prevent your car from being registered.

MORE:

How to register a car

Can I fix the P0605 engine code myself?

Unfortunately, you cannot fix a P0605 engine code by yourself. While you may be able to solve the problem yourself if the issue is related to strengthening electrical connections in your ECM, identifying such an issue requires specialized knowledge of the situation.

Additionally, fixing the ECM requires the following:

Specific tools for installation

Specialized knowledge of ECM software

While it’s rare, you may also need to

replace sensitive electrical components

. If possible, you should let a professional repair your P0605 engine code.

MORE: How to decide if you should take your car to a repair shop or a mobile mechanic

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