Posted on November 18, 2015November 8, 2016 by Stephen Darby

P0606 Engine Control Module/Powertrain Control Module Processor Fault

By Stephen Darby (Contact Me)
Last Updated 2016-11-08
ASE Master Tech

What Does Code P0606 Mean?

I have found that when a code P0606 is stored, it means that the engine control module (ECM)/powertrain control module (PCM) has detected a processor malfunction. Other control modules, including the transmission control module (TCM), body control module (BCM), antilock brake system (ABSCM) module, the traction control system (TCSCM) module, the instrument panel control module (IPCM), the anti theft module (ATM), and many others, may also detect a problem with the processor and cause a code P0606 to be stored.

OBD II equipped vehicles typically refer to the primary powertrain controller as the PCM. The primary focus of the PCM is to control operation of the engine and transmission but it also controls various functions of the other electronic systems listed above. That is not to say that these systems will not also have their own dedicated controller and it is very likely that they will. Information (data) is shared between these controllers using a large and complex web of wiring known as the controller area network (CAN).

When the ignition switch is turned on, before the engine is even started, the PCM begins a series of self tests to determine whether or not it is functioning properly.

If the PCM detects a voltage supply malfunction, a system ground deficiency, or an internal processor error, a code P0606 will be stored and a malfunction indicator lamp (MIL) may be illuminated. Depending upon the perceived severity of the malfunction, multiple ignition cycles (with a malfunction) may be necessary for MIL illumination.

What are the common causes of code P0606 ?

• Blown ECM/PCM fuse
• Bad ECM/PCM power supply relay
• A defective ECM/PCM
• Open or shorted wiring or connectors in the CAN harness
• Insecure control module ground strap or broken ground wire

What are the symptoms of code P0606 ?

• Multiple and varied engine drivability issues
• Harsh or erratic automatic transmission shifting
• Diminished fuel economy
• The engine could stall or run roughly (especially at idle)
• Hesitation upon acceleration
• Other (ABS, TCS, IPC, BCM, or TCM) issues may be exhibited
• ABS, TCS, IPC, BCM, or TCM codes may also be stored

How do you troubleshoot code P0606 ?

Diagnosing a code P0606 can propose quite a challenge, even to the most experienced and well equipped technician. Nevertheless, there are a few preliminary tests that can be performed before throwing your hands in the air and declaring the PCM (or ECM) defective.

For this you will need a diagnostic scanner, a digital volt/ohmmeter (DVOM), and a vehicle information source like All Data (DIY).

Begin with a visual inspection of any visible wiring and harnesses related to the vehicle controllers (some vehicles may have as many as eighteen). Locate and check chassis and engine ground junctions and use the DVOM to make sure that they are clean and secure. Gain access to the ECM/PCM and inspect it for signs of water, heat, or collision damage. If the PCM is damaged, especially by water, assume that it will need to be replaced.

Next, you will want to test ECM/PCM power supply fuses and relays. Test and replace blown fuses, keeping in mind that blown fuses are caused by shorted circuits or shorted components. Consult the vehicle information source for relay connector face views and test them as recommended. If there is an ECM/PCM power supply code present, you will want to diagnose and repair it before attempting to diagnose a P0606.

If power and grounds for the ECM/PCM are intact, suspect a defective ECM/PCM. ECM/PCM (or any other controller) replacement will usually require vehicle match programming. This can be done through your local dealership or you can opt to purchase a pre-programmed controller. You will need to provide the parts supplier with the service number from the original controller, the vehicle identification number, and the mileage of the vehicle, among other things. IF a pre-programmed ECM/PCM is available for your vehicle the parts supplier will advise you of the exact information required.

Codes Related to P0606

• P0600 Serial Communication Link Malfunction
• 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
• P0607 Control Module Performance
• P0685 ECM/PCM Power Relay Control Circuit Open
• P0686 ECM/PCM Power Relay Control Circuit Low
• P0687 ECM/PCM Power Relay Control Circuit High
• P0688 ECM/PCM Power Relay Sense Circuit Open
• P0689 ECM/PCM Power Relay Sense Circuit Low
• P068A ECM/PCM Power Relay De-Energized Performance – Too Early
• P068B ECM/PCM Power Relay De-Energized Performance – Too Late

BAT Team Discussions for P0606

• 2008 Grand Prix 3.8l ignition interlock issues?
  Code P0606 is for TAC(throttle actuator control). The flow chart seems to want to reprogram before PCM replacement. Also, I have seen many electronic throttle actuators with stripped gears or heavy carbon build up or loose connections at TAC module connector. Pull on them lightly to see if any are...