P0605 – Engine control module (ECM) -ROM error

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By John Ingalls (Contact Me)
Last Updated 2016-07-08
Retired military veteran and former Automotive Service Department Manager
CodeFault LocationProbable Cause
P0605 Engine control module (ECM) -ROM error
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Table of Contents

  1. What Does Code P0605 Mean?
  2. What are the common causes of code P0605 ?
  3. What are the symptoms of code P0605 ?
  4. How do you troubleshoot code P0605 ?
  5. Codes Related to P0605
  6. Get Help with P0605

What Does Code P0605 Mean?

P0605 is a generic OBD II powertrain code that applies to all makes and models of vehicles 1996 and newer. This code means that a control module read only memory error has been detected. The issue may be in the Power Control Module (PCM) or one of the other supporting control modules. Depending on the year, make and model of the vehicle it may incorporate several independent control modules. Some of the most common examples are the transmission control module, the body control module or fuel injection control module and the anti-lock brake control module. These modules are monitored by the PCM at all levels of vehicle operation and even at idle. The PCM translates these readings and makes adjustments to power inputs to control fuel pressure, shifting and anti-lock brake operation. OBD II error code P0605 indicates that the PCM has lost the ability to monitor one or more control modules. This means the ability to adjust the control module for the automobile to operate correctly has been disabled. Other control modules may be incorporated to support additional features such as a turbocharger, traction control and cruise control. As technology advances, driver-assist features increase and the list of control modules required continues to grow.


What are the common causes of code P0605 ?

A lot of P0605 error code issues are simple in nature such as a loose connection, defective wiring harness or a broken wire. Corrosion is also a huge issue when it comes to malfunctions associated to PCM and control module problems. Some control modules may be exposed to the elements causing corrosion issues. PCM’s are normally high and dry unless you have a heater core issue that is one of the reasons a PCM may need to be replaced. Ground issues are one of the main causes of power loss to PCM’s and control modules that must be grounded to operate. Loose ground straps are very common and are caused by road vibration. Some PCM’s and control modules are grounded through the case or cover. When the mounting bolts become damaged or loose these components are no longer grounded and the power input is disabled. PCM flashing is often required to reset the control module. Software upgrades are very common as well and are developed by the manufacture to correct known issues. Stored errors codes that are not cleared commonly cause a P0605 error code. Of course, sometimes PCM’s and control modules experience internal failure and must be replaced.

Common Misdiagnosis

Stored error codes can often lead to a misdiagnosis for the OBDII P0605 error code. You should use freeze frame data to determine which codes were stored first. Engine misfire codes, lean exhaust codes, fuel injector codes, and other drivability or transmission codes can also be present interfering with the troubleshooting process. You should diagnose codes in the order that they are stored. This will improve your chances for a successful diagnosis.

What are the symptoms of code P0605 ?

Check engine light on:

The ECM will detect the control module read only memory error and illuminate the check engine light. This is to alert you of the issue and prompt you to have the system scanned as soon as possible.

Decreased fuel economy:

Decreased fuel economy is common to all performance issues and the P0605 code is not an exception to that rule. In this situation, fuel consumption can be affected by multiple sources. The fuel pressure to the injectors or fuel to the throttle body may be at the wrong level. The transmission could be hanging in gear for too long burning more fuel. The list goes on and on.

Harsh shifting or transmission hesitation:

Harsh shifting or transmission hesitation will occur if the PCM or the transmission control module is not functioning properly. This situation can cause extensive damage to the transmission and requires immediate attention.

Poor Acceleration, rough idle or stalling:

This is an indication that the ability of the PCM or fuel control Module is be affected due to a defect or other associated components.

Anti-lock brake system not activating:

This situation verifies that the malfunction is affecting the anti-lock brake system. It could be a PCM or an anti-lock brake control module issue.

Optional features are not functioning properly:

If advanced features such as a turbo charger, the cruise control module or driver- assist features are not working. This all goes back to the PCM which is brain of the operation. The problem may be isolated to the specific system is some scenarios.

How do you troubleshoot code P0605 ?

The best starting point is the PCM:

  • Inspect for physical damage

  • Check power input

  • Inspect wiring and connections

  • Check tech bulletins for software updates

  • Flash the PCM if recommended

  • Make sure it is grounded

Check the control module for the system malfunctioning:

  • Check tech bulletins

  • Inspect for physical damage

  • Check power input

  • Inspect wiring and connections

  • Check function if it’s mechanical

  • Make sure it is grounded


P0600 – Serial Communication Link
P0601 – Internal Control Module Memory Check Sum Error
P0602 – Control Module Programming Error
P0603 – Internal Control Module Keep Alive Memory (KAM) Error
P0604 – Internal Control Module Random Access Memory (RAM) Error
P0605 – Internal Control Module Read Only Memory (ROM) Error
P0606 – ECM/PCM Processor
P0607 – Control Module Performance
P0608 – Control Module VSS Output ‘A’
P0609 – Control Module VSS Output ‘B’
P0610 – Control Module Vehicle Options Error

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