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  • The P2502 code is defined as Charging System Voltage. This code triggers when the charging system voltage falls below a certain threshold for a certain amount of time.
  • The P2502 code can be caused by a faulty alternator, a dead battery, faulty wiring, or issues with the powertrain control module or charging system.
  • The P2502 code can have symptoms like an illuminated check engine light, an illuminated charging system warning light, stalling, a no-start condition, and malfunctioning onboard electronics.

Vehicles are equipped with an alternator that converts the mechanical energy generated by the engine into electrical energy. Like generators, alternators pass magnets over coils to generate current that’s used to charge the battery and power various electronics. Problems with the charging system can trigger the P2502 or other related trouble codes.

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What Does the P2502 Code Mean?

The P2502 code is defined as Charging System Voltage. This code triggers when the charging system voltage falls below a certain threshold for a certain amount of time. This can either be caused by an old battery that refuses to hold a charge or an issue with either the alternator or other parts of the charging system.

close up shot of a car alternator
The P2502 code means that your vehicle has a charging system issue.

Note: The definition of the P2502 code can be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

What are the Common Causes of the P2502 Code?

The issues that trigger a P2502 code can be caused by the following:

What are the Common Symptoms of the P2502 Code?

The P2502’s symptoms include the following:

How to Diagnose the P2502 Code

The P2502 code might be commonly caused by a faulty alternator, but it can also be caused by other issues. You’ll need to identify which part is problematic to determine the proper course of action. Otherwise, you might end up fixing or replacing a functional component.

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Accessing and testing components might require the use of specialized tools and knowledge. If you find this task daunting, don’t hesitate to reach out to a professional mechanic.

car alternator and battery images
A faulty alternator or battery may cause the P2502 code to register.

How to Fix the P2502 Code

The P2502 might have a list of common causes, but there isn’t a single procedure that can cure those issues. Repair procedures vary depending on the vehicle model, design, and layout. Sometimes, a trouble code can also trigger several related trouble codes. When this happens, you might need to fix the problems in the appropriate order dictated by the manufacturer. To learn about possible solutions, consult reputable internet repair resources and how-to guides. When your scan tool shows diagnostic trouble codes, don’t forget to consult your vehicle’s repair manual.

It’s best to consult a professional mechanic if you don’t have much experience diagnosing or correcting error codes.

A Closer Look at the Charging System

Before power is directed to your vehicle’s battery, the alternating current (AC) from the alternator needs to be transformed into direct current (DC) using a rectifier. A voltage regulator controls the voltage directed into the battery.

See also  Charging Systems

A functioning but discharged battery should be able to convert all of the current produced by the charging system into stored chemical energy. However, a faulty battery won’t be able to store all the energy and a voltmeter connected to a faulty battery will indicate a low charging voltage. 

To identify the issues causing the P2502 code, a mechanic might need to test the charging system and the battery. Remember that diagnosing a faulty charging system will require a functioning and charged battery to get an accurate test result. When a discharged battery is used during charging system testing, the tests could incorrectly indicate a faulty alternator or voltage regulator.

About The Authors
Written By Automotive and Tech Writers

The Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Reviewed By Contact Center Manager and Technical Reviewer at

William “Bill” Guzenski has produced hundreds of how-to videos for the automotive community. He’s an ASE Certified Master Automobile Technician, and is affiliated with the Specialty Equipment Market Association (SEMA). He loves attending race events and car shows throughout the country, as well as traveling in his 40-foot motorhome, exploring abandoned mines and ghost towns.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

File Under : OBD-II Trouble Codes Tagged With : ,
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