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P0603 Severity
Identifying an OBD code is just the start of a complete diagnostic routine. Most trouble codes are caused by a sensor reporting a value that is out of range. Just replacing a sensor may not fix underlying issues. Be sure to understand the code, the part or system in your car that the code refers to, and the risks of delaying professional repair.
Proper diagnosis will save you time and money on unnecessary repairs.
Urgent codes indicate immediate action is necessary. These are urgent and significant malfunctions that can cause severe damage to the vehicle or harm the driver and passengers.
The engine control module (PCM) performs many vital functions in a modern vehicle, including management of the Fuel and Ignition Systems. When the PCM loses communication with one or more control modules it will set code P0603.
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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.
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.