Error Code P0605 is defined Internal Control Module ROM (ROM) Error. This refers to a fault in the internal control module in ROM in PCM, usually caused by disrupted or loss of stored memory.

This error code is a genetic trouble code, meaning it applies to all vehicles equipped with OBD-II system, particularly vehicles made since 1996 up to present. Specifications on the definition, troubleshooting and repairs of course, vary from one vehicle make and/or model to another.


The PCM (powertrain control module, also known as ECM or engine control module) is the electric brain of the vehicle, which controls several functions such as ignition timing, fuel injection, fuel mix, anti-lock braking, electronic power steering (for most new vehicle models), traction control, cooling fan operation, emission controls, etc. Even for smaller functions, such as horn, radio and window operation.

The ROM consist the memory of parameters that can’t be erased. The Parameters include tests and numeric ranges that the PCM permanently stores for use each time the vehicle is used in any way. These parameters are the guidelines on how the processor should interpret the codes and values being sent from but not limited to, MAF (mass air flow sensors), O2 (oxygen) sensors, crank position sensor, interior buttons, and various forms of engine management.

If the information sent to the PCM doesn’t match the values stored in the processor by the manufacturer, the Check Engine light will be triggered, as this can mean disruption or loss of stored memory, which would set the Error Code P0605.

Other related internal control module error codes include:

Common Symptoms

Error Code P0605 doesn’t come with a lot of symptoms, and its symptoms are pretty common, including:

  • Engine misfire
  • No start condition
  • Engine hesitation or stalling

Possible Causes

Error Code P0605 can be caused by a lot of factors, such as:

  • Defective or interrupted PCM ground or power supply
  • Broken solder points on the circuit board or the PCM caused by head or vibrations
  • Loss of memory in the PCM
  • Outdated PCM

How to Check

Diagnosis for this code is simple:

First, technicians check the related TSBs (Technical Service Bulletin) and recalls to determine if the PCM needs an update, reprogramming or flash

Then, they check the wires connecting to the PCM, including all electrical terminals

Next, they test the PCM for proper ground points and power supplies

How to Fix

Repairs for this code are as easy as its diagnosis, which includes:

  • Repair of faulty ground or power supply such as damaged or corroded wiring
  • PCM update, reprogram or reflash (if applicable)
  • Replacement of PCM

As said earlier, Error Code P0605 is easy to diagnose and repair. However, many people fail in their repair by simply ignoring the first step – failing to research whether there is a TSB or recall related to update, reflash or reprogram the PCM. Also, they assume the PCM is bad and replace it, without testing the power supply and grounds.

Error Code P0605 is a serious problem, since it can affect other functions of the vehicle. Thus, it must be fixed ASAP.