What does it mean?
SPECIAL NOTES: Due to the highly technical nature of modern automotive electrical systems in general, and charging systems in particular, non-professional mechanics should take note that diagnosing/repairing charging systems beyond the basic, generic steps outlined in this guide is NOT recommended.
In addition, non-professional mechanics are strongly urged to both read the section dealing with the working of the charging system of the application being worked on, and to gain a full understanding of the charging system (its components, and how the various components of the charging system interact with each other), before attempting a diagnosis and/or repair of code P0563.
Failure to gain at least a working knowledge of how the charging system works will almost certainly result in a misdiagnosis and/or potentially fatal damage to the electrical system. Be aware that the information provided in this guide is intended for general informational purposes only, and as such, it should NOT be used in any diagnostic or repair procedure for code P0563 without proper reference to the repair manual for the application being worked on.
Refer to the “Troubleshooting” section of this guide for specific tips, advice, and warnings. END OF SPECIAL NOTES. OBD II fault code P0563 is a generic code that is sometimes defined as “System voltage – high”, but more commonly as “ECM/PCM Power source circuit- unexpected voltage”. Regardless of the actual wording of the definition though, code P0563 is set when the PCM (Powertrain Control Module) detects an abnormal voltage from either the charging system, or the battery, and sometimes both.
Note that depending on the application and the exact nature of the problem, the battery warning light will illuminate when code P0563 sets on some applications, while on others, the CHECK/SERVICE ENGINE SOON lamp will illuminate. NOTE #1: The acronym “ECM” stands for either “ E ngine, or E lectronic C ontrol M odule, which is just another name for the PCM. One other commonly used acronym for the PCM is “ECU”, which stands for E ngine C ontrol U nit.
NOTE #2: Older applications used the definition “System voltage – high” for code P0563, which specifically referred to abnormally high system voltages, but this definition was largely supplanted on some applications by the more encompassing “ECM/PCM Power source circuit- unexpected voltage” as electrical systems grew in complexity to refer to both abnormally high, and low voltages, and specifically between the PCM and the battery.
In practice, the PCM depends on a specified current being supplied by the battery even when the ignition is switched off to keep critical systems powered up, as well as to be able to store fuel trim data, idling speed settings, DTC history and associated freeze frame data, among other data sets. Thus, when the PCM detects that the required (specified) level of power is not being supplied by the battery, it will set code P0563, and illuminate a warning light.
In addition, when the ignition is switched to the “ON” position, the PCM performs a number of self- tests and other checks to ensure that all relevant systems and/or control modules have access to sufficient power from the battery to perform their various tasks and functions as intended during the start-up cycle.
In this context, the words “ unexpected voltage” in the definition could mean either a high, or a low voltage, although abnormally low voltages occur far more frequently than high voltages, and especially on vehicles where the PCM controls the alternator output, such as on many Chrysler and Mazda applications. In the event of an “unexpected voltage” being present, the PCM may prevent the engine from starting, in addition to setting code P0563 and illuminating a warning light.
Note though that on some applications, the code will be set and a warning light illuminated on the first failure, while on others, the code may only set on the next start-up cycle. Note that depending on the nat