P0563 – System voltage -high


By Reinier (Contact Me)
Last Updated 2016-11-22
Automobile Repair Shop Owner

Trouble CodeFault LocationProbable Cause
P0563 System voltage -high Alternator

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What Does Code P0563 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 “Engine, or Electronic Control Module, which is just another name for the PCM. One other commonly used acronym for the PCM is “ECU”, which stands for Engine Control Unit.

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 nature of the problem and the application, the warning light’s brightness may fluctuate as the engine speed changes.

The image below shows a much-simplified schematic of a typical modern charging system and the direction of current flow when the system is in operation. Note that the “sensing circuit” indicated here can incorporate a dedicated stand-alone control module to estimate the output required from the alternator, and then to regulate the alternators’ output, or it can include dedicated control circuits in the PCM, such as on some Chrysler and Mazda applications.


What are the common causes of code P0563 ?

The most common causes of P0563 are defective batteries and alternators, but other possible causes could include the following-

  • Damaged, burnt, shorted, and/or corroded wiring and connectors, including corrosion of the battery terminals
  • Open circuits in the PCM’s power supply circuit
  • Loss of engine and/or body ground
  • High resistances caused by poor connections between the battery terminals and battery posts
  • Large parasitic current drains on the battery
  • Poor installation of aftermarket accessories like audio systems, auxiliary driving lights and the like

What are the symptoms of code P0563 ?

In some cases, there may be symptoms present other than a stored trouble code and an illuminated warning light. Other possible symptoms could include the following, but note that not all the symptoms listed here will always be present on all applications.

  • Battery may partially or sometimes fully discharge, over periods that range from hours to several days.
  • Battery failure caused by overcharging.
  • Frequent or unpredictable stalling of the engine due to low battery power.
  • Automatic transmission may shift erratically, unpredictably, or not at all, depending on the application and the exact nature of the problem. Note that some applications may enter limp mode if the transmission is affected.
  • Various forms of damage to the electrical system can occur due to either low or excessively high system voltages. Typical damage includes loss of memory or programming by control modules (including the PCM), erratic / sporadic failures of the security system, and even damage to the starter motor caused by low system voltages, especially on diesel applications.
  • Glow plug operation may be affected on diesel applications.

How do you troubleshoot code P0563 ?

SPECIAL NOTES: Although an alternator’s output is typically between about 1 volt, and 2 volts higher than the battery’s rated voltage, many factors, such as the current load(s) placed on the battery as well as ambient temperature, engine speed, the temperature of the battery and the alternator, and even the type, age and state of charge of the battery can influence the alternator’s actual output significantly, and for varying lengths of time.

Non-professional mechanics should therefore take note that a charging voltage that exceeds the oft-stated “magic” value of 13.8, to 14.6 volts does not necessarily indicate a malfunction, and no conclusions as to the serviceability (or otherwise) of any component of the charging system should be drawn on the basis of a higher reading without proper reference to the repair manual, and due consideration of all environmental factors that could influence the alternator’s actual output at any time. END OF SPECIAL NOTES.

WARNING:  When diagnosing code P0563, do NOT disconnect the battery to “test” the alternator on ANY application while the engine is running. Doing so could damage or even destroy not only the alternator, but also other components, such as control modules due to the voltage spike that occurs when the battery is disconnected. Moreover, never disconnect the battery even when the engine is not running, unless the manual expressly states that the battery must be disconnected at that point in the diagnostic procedure, and be sure to install a memory saving device if the manual calls                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               for such a device to be installed. Memory-saving devices keep critical systems powered up when battery power is removed, and failure to install such a device could cause the PCM and/or other controllers to lose vital programming and/or memory.

NOTE #1: Since diagnosing/repairing code P0563 will almost certainly involve testing the operation of the alternator, bear in mind that on applications where the PCM controls the alternator’s output, these alternators cannot be tested on a test bench after repairs. In fact, there is no reliable way to test PCM-controlled alternators except by installing them on the vehicle, meaning that if the alternator is shown to be defective, the best course of action is to replace the defective alternator with an OEM part, or with a unit that is rebuilt to OEM specifications and standards.

NOTE #2: Successfully diagnosing code P0563 requires that the battery be fully charged, and in proper working order. This can be tested and verified with a good quality load tester, but if such a tool is not available, the battery MUST be inspected and tested by a specialist battery dealer or competent repair shop before proceeding with the diagnostic process. If the battery proves to be defective, replacing it will likely resolve the code, although this is not guaranteed.

Step 1

Record all fault codes present, as well as all available freeze frame data. This information can be of use should an intermittent fault be diagnosed later on.

NOTE: Since loss of ground is a major cause of this code, use this opportunity to inspect both the engine and body ground cables/connections, but be sure to install a memory saving device before disconnecting the ground cables. Clean all connection points, and make sure all connections are tightened properly. Clear the code(s), and rescan the system to see if the code returns.

Step 2

If any other codes are present along with P0563, note the order in which they were stored, and resolve all other codes in this order, since one or more of the other codes could have been the cause of P0563.

If however, there are no other codes present, now would be a good time to inspect the battery terminals for corrosion, since many, if not most electrical issues stem from corroded and/or improperly fastened battery terminals. However, do NOT remove any battery terminal without first installing a memory saving device to prevent the PCM and other controllers from losing memory or programming.

Only remove the battery terminals in the order specified in the manual after the memory saving device is installed. Use a solution of baking soda and luke-warm water to remove deposits of acid from the battery posts, and reconnect the terminals in the reverse order of removal. Make sure the terminals are tightened properly, and apply either a coat of dielectric grease or an approved battery sealing spray over the terminals to prevent further acid accumulations. Remove the memory saving device, and rescan the system to see if the code returns.

NOTE: Rinse the battery and surrounding area with clean water to remove all acid residues, and make sure the battery is dry before reconnecting the terminals.

Step 3

If the code persists, and the battery is known to be good, perform a thorough visual inspection of all wiring between the battery and the alternator. Look for obvious signs of trouble like discoloration around wire/cable terminations that would indicate poor contact and overheating, shorted, damaged, and/or corroded wiring and connectors. Make repairs as required, clear all codes, and rescan the system to see if any codes return.

NOTE: Include the alternators’ drive belt in this inspection. Check the belt for damage such as fraying, or glazing caused by slippage and correct the belt tension if required. Note that this could require the replacement of both the drive belt and the automatic tensioning device. Consult the manual on the correct procedure(s) to carry out these replacements, or refer the vehicle for professional diagnosis and repair.

Step 4

If the code persists, consult the manual on the specified charging values for the application, start the engine, and prepare to test the output from the alternator with a digital multimeter.

Let the engine idle, set the multimeter to the appropriate DC setting, and place the red probe on the positive battery post, and the black probe on the negative post. The reading displayed on the multimeter should fall within the specified range, but keep the probes on the battery posts for at least 60 seconds, since the PCM may adapt the alternators’ output for any number of valid reasons. Take the final reading only when the displayed reading has stabilized, and note the voltage for future reference.

A properly functioning alternator should never generate less than about 13.5 volts, or more than 15 volts, depending on the type of battery, the battery’s state of charge, and the current load(s) placed on the battery. However, there is no single “magic” or fixed value that applies to all applications under all possible conditions, so consult the manual for the application to determine the ideal charging rate for that application.

In addition, bear in mind that the manual may prescribe that the alternator be tested at specified engine speeds, and with certain electrical consumers being in operation. Follow these directions exactly to get reliable and accurate results.

NOTE #1: Note that in some circumstances, the alternator could deliver more than 15 volts. This is not necessarily indicative of a problem or malfunction but to be sure that it is not, consult the manual on both the maximum allowable charging rate for the application, as well as the maximum allowable time the high voltage is allowed for. Also, note that over charging conditions are usually not indicated by a warning light.

NOTE #2: If the alternator delivers more than 15 volts for more than about 60 seconds or so after start-up, it is almost certain that the voltage regulator is defective. This is a serious condition if the alternator output is controlled by the PCM or other controller, since the high voltage could damage controllers and other components, including the battery. On many applications, the voltage regulator is easily accessible (and replaceable), so replace it by following the instructions in the manual. Clear all codes, and retest the system to verify that the alternator output falls within the manufacturers’ specifications.
NOTE #3: Do not place the probes on the battery terminals, since the object of the test is to see how much current reaches the battery. Testing the output voltage on the terminals could give false or misleading readings, especially if contact between the terminals and the battery terminals is not perfect.

Step 5

If however, the alternators’ output is lower than the value specified in the manual, test the unit’s output at the point where the cable leading to the battery positive terminal attaches to the alternator. This terminal will be marked with either a big + symbol, or with the letters BATT+. Place the red probe of the multimeter on the cable termination, and the black probe on the battery negative post.

There will be slight difference between this reading and the reading obtained across the battery posts, but this difference should not be bigger than about 0.2 volts. If the difference exceeds this value, it is likely that a high resistance in the cable is causing a severe voltage drop, which could be big enough to prevent the battery being charged properly.

Inspect all connections on this cable, but do NOT disconnect any connection while the engine is running, the ignition is switched on, or without a memory saving device being installed. If all connections are found to be sound, follow the directions in the manual to test the cables’ resistance, and replace the cable if its resistance does not agree with the value stated in the manual. Repeat this step after the cable replacement to verify that the correct voltage reaches the battery.

NOTE: If there is no voltage from an alternator at the BATT+ terminal, the warning light will burn steadily, which means that the alternator is defective, and is not charging at all. It may be possible to repair/rebuild the alternator, but in the end, it is often more cost effective to replace the defective alternator with an OEM part.

Step 6

If the warning light remains illuminated, or if it dims in response to changes in the engine speed, the most likely cause is a failure of one or more of the diodes in the rectifier that changes the current from AC to DC.

While it is possible to replace the rectifier as a complete unit on a DIY basis, the process involves disassembly of the alternator. If you are not comfortable with the idea of removing the alternator from the engine, stripping it down, de-soldering the rectifier, and then assembling the alternator after the rectifier replacement, and then to reinstall the alternator, refer he vehicle to a competent repair shop for professional diagnosis and repair.

Step 7

If none of the above steps have revealed any obvious causes of P0563, the problem is likely to be caused by a parasitic drain on the battery. Depending on the exact nature of the problem, a parasitic drain can cause the battery to discharge in anything from a few hours to a few days.

If a parasitic drain is suspected, turn off all electric consumers, but leave the multimeter connected to the battery. Set the meter to the appropriate DC voltage setting, but ensure that the probes are in firm contact with the battery terminals or post.

Bear in mind that most applications make standby power available to various accessories like power windows (and others) so the initial drain on the battery might be significant for the first 30 -, to 60 seconds or so after the ignition is turned off. However, some electrical consumers, like the Keep Alive Memory in the PCM, draws current continuously, but this current draw is normally miniscule, and measured on the milli-volt scale. Consult the manual on the exact maximum allowable drain value for the application, and note this value for future reference.

Depending on the application, the current drawn by the PCM is typically only a few hundred milli-volts but bear in mind that tracking devices, some aftermarket audio system components, the security system, and modifications to the electrical system in general could contribute to the parasitic current draw to the point where the battery could be discharged to below the critical level set by the manufacturer in a matter of hours, which will set code P0563 every time it happens.

Thus, disconnect all aftermarket accessories and/or components and monitor the continual current draw on the battery with the multi-meter. Verify that the draw falls within the specified range, but if it does not, start pulling fuses one by one until the current draw either stops completely, or falls to within acceptable limits. This process of elimination is the quickest way to identify the circuit with the problem, which is almost always a short circuit, or a poor ground connection.

Be aware though that identifying the actual problem might be extremely challenging and time consuming, so unless the cause is obvious, the better option might be to refer the vehicle for professional diagnosis and repair.

Step 8

On applications where the alternator is not controlled by the PCM, the above steps should resolve almost all possible causes of code P0563. However, on applications where the alternator is controlled by the PCM or other controller, the cause of the code might involve software failures or malfunctions in the controller, which happens more frequently than one might suppose.

In these cases, replacing or reprogramming the PCM is required, but bear in mind that the placement PCM needs to be integrated into the CAN (Controller Area Network) bus system, which means that this procedure is best left to competent professionals who have access to the required equipment and the latest software.

Codes Related to P0563

  • P0560Relates toSystem Voltage [Malfunction]”
  • P0561Relates toSystem Voltage Unstable”
  • P0562Relates toSystem Voltage Low”

NOTE: Be aware that there does not appear to be a uniform definition of P0563 and its related codes. On some applications, one or more of the codes listed above may be defined as “ECM/PCM Power source circuit- unexpected voltage”, while on others, the definitions are as listed in this section. Also, note that there are other definitions such as “CHARGING SYSTEM LOW/ [HIGH/UNSTABLE] VOLTAGE” listed, but regardless of the actual wording of the definition, the meaning is the same in all cases, i.e., there is a problem of some kind in the charging system of the application that produces abnormal voltages.

BAT Team Discussions for P0563

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