Error Code P0600 is defined as Serial Communication Link Malfunction. Meaning, it refers to a malfunction of the communication link of the PCM and one of its supporting control units. This code is a generic trouble code by design, and encompasses all computer-controlled vehicles. Specifications on the definition, troubleshooting and repairs will vary depending on the make and/or model of the vehicle.

Chrysler: PCM Fault, SPI Communications Conditions

GM: Loss of Serial Communication Link Conditions

Infiniti: AT communication – circuit malfunction

Nissan: ECM/TCM – communication malfunction


Most vehicles’ PCM (powertrain control module, also known as ECM or engine control module in other vehicles makes) controls as many as 18 actuators, through a controller network (Can Bus Automotive Network), which is a series of wiring harness from the PCM to the controllers.

Error Code P0600 means the PCM has lost its communication or connection of any of its several controllers more than once. When this code is set, the Check Engine light on the dashboard will be triggered and the vehicle will be put on failsafe mode. This is to prevent further damage and protect the vehicle. Failsafe mode will remain until normal operation is detected through repair.

The controllers operated by the PCM are known as modules, and it controls majority of the functions of the vehicle. Some of these associated control modules are:

  • ABS brakes
  • Air conditioning
  • Anti-theft Sunroof and seat position
  • Body ride control
  • Cruise control
  • Fuel injection system
  • Ignition system
  • Power windows Traction control systems
  • Proximity alerts
  • Transmission shift points
  • Turbo charger Emission systems
  • Variable camshaft timing

These are just few of the many available computer controlled options available in newer vehicle models today.

Common Symptoms

Error Code P0600 is quite tricky, as it can mean various failures in the communication. For example, failed fuel injector or an ignition system failure can lead to a misfire. An inexperienced technician may start its diagnosis in the affected system, rather than checking communication loss. If the PCM is not controlling the ignition control module, or grounding the fuel injector, then a misfire will take place. This however, is not a fault with the system, rather with the control system itself. Depending on the exact location of the failure, some of these symptoms may be present:

  • Check Engine light illuminated
  • ABS light illuminated
  • Transmission light illuminated (not shifting properly)
  • Decrease in fuel efficiency
  • Vehicle stalls at an idle
  • Poor acceleration
  • Rough running
  • Problems that indicates possible communication loss in the area

Possible Causes

Poor connection or faulty PCM is the most common cause of this error code. For the most part, PCM works as a ground to control these components and modules, rather than supplying power to them.

Corroded or loose connector is highly more likely than broken or frayed wires between the two devices, as well as poor ground. The PCM and the activator modules definitely need good ground to work properly.

Other possible causes include:

  • Low battery voltage
  • Poor electrical connection (open PCM wiring harness, short)

How to Check

To diagnose this error code, first technicians use a scan tool to check for any stored (history and pending codes). They will also check the freeze frame data for every code to see what conditions the vehicle was under when the code was triggered.

Next, all codes will be cleared and the vehicle will be taken for a test drive to duplicate the conditions.

Then, technicians will conduct a visual inspection and look for signs of damage, wear and tear and loose components of the suspected affected components.

Then, they will check the battery voltage to make sure it’s within the manufacturer’s specifications.

Next, they will use a multimeter to check for proper continuity of the PCM’s power and ground circuits.

Lastly, they will conduct the manufacturer’s PCM testing procedure. This may vary from one vehicle to another, depending on the make and/or model.

How to Fix

Repairs for P0600 are fairly easy, which of course, can only be derived from a thorough diagnosis. Some of the repairs include:

  • Replacing the faulty PCM
  • Repairing or replacing PCM wiring harness
  • Diagnosing and repairing the cause of low battery voltage
  • Fixing poor electrical connections

Error Code P0600 can cause intermittent erratic symptoms that can definitely affect the vehicle’s normal operation. In severe cases, the vehicle must NOT be driven until the problem is fixed.

Also, the ABS system and traction control system can be disabled by this error code, thus, driving in poor weather condition must be avoided if the ABS light and Traction Control light is illuminated on the dashboard.