Overview is defined as PCM Processor Fault. This code means there’s an internal integrity fault in the PCM.

This error code is a generic 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 vary from one vehicle make and/or model to another.


The PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes) is referred as the ‘electrical brain’ of the vehicle. And with that, it is responsible for monitoring every aspect of the vehicle’s engine and electrical system.

When the vehicle starts, the PCM will automatically perform a self-check to make sure all of the components of the engine are running properly. If the result of the self-check indicates a problem in the PCM, then it will store the Error Code P0606.

When this code is activated, it should be able to store freeze frame data to help technicians with an advance scanning tool to get the information to determine what is exactly wrong with the vehicle when the code was triggered.

Common Symptoms

As with other codes that concerns a fault in the PCM, Error Code P0606 triggers the Check Engine light and other fault indication lights, such as ABS (anti-lock brake) light. Other symptoms include:

  • Vehicle stalls or shifts improperly
  • Engine dies when vehicle comes to stop
  • Misfire symptoms
  • Increase in fuel consumption

In rare cases, the vehicle may not exhibit noticeable symptoms.

Possible Causes

The most common cause for this error code is failed PCM, which can of course, happen from different factors such as:

  • Broken, corroded or frayed wires in the PCM
  • Broken, corroded or frayed connectors in the PCM
  • Faulty PCM ground circuit and/or output devices
  • Faulty CAN (controller area network) bus communication

How to Check

To diagnose this error code, technicians start by retrieving freeze frame data using OBD-II scanner, which will give them enough information to know when the PCM set the code and its causes.

Then, they proceed on checking the wires and connectors that leads to the PCM and look for signs of breakage, corrosion or frayed wirings.

Then, after repairing or replacing faulty connectors and wires, they retest the system. In most cases, they reprogram the PCM, or even replace.

Or, they check with the dealer to see if there are recalls or if the PCM can be replaced under emission warranty.

How to Fix

Repairs for this error code are pretty simple, which include:

  • Repair or replacement of broken or frayed wires
  • Repair or replacement of broken or corroded connectors
  • Repair or replacement of faulty PCM ground circuits
  • PCM replacement or reprogramming

Error Code P0606 is very straightforward, and easy to diagnose, as it usually indicates a fault in the PCM, which means it should be fixed or reprogrammed. However, some symptoms may be very similar with mechanical problem symptoms, which as a result, people mistake on repairing ignition systems or fuel system components.