What Does P0603 Code Mean?

OBD-II Code P0603 is defined as a Internal Control Module Keep Alive Memory (KAM) Error

The PCM or Power Train Control Module performs many vital functions in a modern vehicle, such as management of the Fuel System, Ignition System, Transmission, Anti-Lock Brake and Traction Control systems. The PCM regularly runs a self-diagnosis function where it performs normal mathematical calculations, and if the results of these calculations are not as expected, a code such as P0603 code will be set. 

Code P0603 means that the PCM's Keep Alive Memory (KAM) self test is failing. This is a routine self test that is performed periodically through out the day. This is critical because the PCM's Keep Alive Memory Modules store all of the PCM's adaptive calculations that need to be 'kept alive' or saved when the vehicle isn't operating. If this part of the PCM's functionality is unreliable, the powertrain's main computer can't be trusted to accurately do its job and may need to be replaced.   

P0603 Symptoms

  • Check Engine Light will illuminate
  • Failure of Emissions Inspections due to OBD-II Monitor issues 
  • ABS/Traction Control Light may illuminate
  • Vehicle may not perform and/or shift properly
  • OBD-II Monitor 'READY' flags go to 'NOT READY' every time key is removed from the ignition
  • Decrease in fuel economy
  • In unusual cases, there are no adverse conditions noticed by the driver
  • In some cases, there may be performance problems, such as dying when coming to a stop and/or misfire-like symptoms

Common Problems That Trigger the P0603 Code

  • Lack of proper voltage to the Keep Alive Memory connection on the PCM  
  • Defective PCM Keep Alive Memory Module (KAM)
  • Defective PCM ground circuit(s)
  • Defective PCM controlled output devices

Common Misdiagnoses

  • PCM is replaced when the root cause is imroper voltage to the PCM KAM circuit
  • PCM is replaced when the root cause is defective PCM ground circuits

Polluting Gases Expelled

  • HCs (Hydrocarbons): Unburned droplets of raw fuel that smell, affect breathing, and contribute to smog
  • CO (Carbon Monoxide): Partially burned fuel that is an odorless and deadly poisonous gas
  • NOX (Oxides of Nitrogen): One of the two ingredients that, when exposed to sunlight, cause smog

P0603 Diagnostic Theory for Shops and Technicians

When the code P0603 is set in the Powertrain Computer, it means that the Powertrain Computer or PCM is failing its Keep Alive Memory self-check and has found errors with the Keep Alive Memory functions.  In many cases, the KAM is not getting an 'always on' 12 volt signal, however in some cases, the actual KAM memory module is defective and the PCM needs to replaced and re-programmed.  But, before you replace the PCM, be sure to check for any shorted output devices that may have cause the KAM functions to fail. 

When diagnosing a P0603 code, it is important to record any other codes and the P0603 freeze frame data. Then one should duplicate the code setting conditions with a test drive. Pay close attention to the engine load, throttle position, RPM, and road speed because a P0603 can be difficult to detect.


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