Skip the auto shop - Our mechanics make house calls

P2504 OBD-II Trouble Code: Charging System Voltage High

check engine light

P2504 code definition

The P2504 OBD-II fault code simply means that an irregularity was detected in the charging system circuit - specifically that the voltage was high. This high voltage reading may have originated from the battery, charging system, or starter.

What the P2504 code means

The P2504 trouble code means that a higher than normal voltage within the charging system was detected. The code alone, however, does not indicate whether this high reading is an intermittent or ongoing issue.

What causes the P2504 code?

Most commonly caused by a faulty alternator or other charging system issue, the PCM detects a voltage higher than the accepted parameters, registers the P2504 code, and then illuminates the Check Engine Light on the vehicle’s dashboard.

What are the symptoms of the P2504 code?

Aside from the illumination of the Check Engine Light, a vehicle registering the P2504 code may also display one or more of the following symptoms:

  • Engine stalling when on idle
  • Decrease in fuel efficiency
  • Improper shifting in a vehicle with an automatic transmission
  • Red battery light may come on the dashboard

How does a mechanic diagnose the P2504 code?

Using a specialized scan tool with a greater sensitivity and scope of application than those found in auto parts stores, a mechanic can verify the existence of the P2504 code. Using the information collected and provided by that scan tool, the mechanic can then use professional reference materials to interpret that data and determine a probable cause for the trouble code registering.

The technician then performs a hands-on inspection of the affected system and most likely culprits, replacing any worn components or making other needed repairs. Afterwards, the mechanic may test drive the vehicle and use the scan tool again to verify that the issue has been resolved.

Common mistakes when diagnosing the P2504 code

The most frequent mistakes a mechanic may make within a P2504 trouble code diagnosis are:

  • Not verifying the existence of the P2504 code

  • Failing to test the alternator and unnecessarily replacing the battery or starter

  • Failing to thoroughly inspect the alternator, battery and related charging system components

  • Forgetting to clear the P2504 OBD-II fault code after making needed repairs

How serious is the P2504 code?

Since the P2504 code registers due to voltage abnormalities in the alternator, battery, or charging system, the problem can worsen over time, ultimately preventing a vehicle from starting or staying running. If the issue is left neglected, such voltage spikes may affect other components or systems, resulting in more costly repairs down the road.

What repairs can fix the P2504 code?

After the validation of the P2504 code by a qualified mechanic in possession of a specialized scan tool, the following repair(s) may be required:

  • Reinstalling primary or secondary grounds
  • Repairing wiring or battery cables
  • Replacing corroded battery terminal ends
  • Replacing an alternator, battery, or starter
  • Replacing a defective voltage regulator
  • Replacing a faulty PCM in rare cases

Additional comments for consideration regarding the P2504 code

Since there are multiple potential causes of the P2504 code registering, it can take up to several hours for a qualified mechanic to accurately diagnose the cause of the fault code. Multiple scans and other tests may be in order even after repairs have been made to verify the issue has been satisfactorily resolved.

Need help with a P2504 code?

Let YourMechanic connect you with an experienced and qualified mechanic to diagnose and repair the cause of the P2504 code in your vehicle. If needed, that technician can even come to you at your home or office for your convenience and safety. Receive a quote, book an appointment with a mechanic online or talk with a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...
P0291OBD-II Trouble Code: Cylinder 11 Injector Circuit Low
P0291 code definition When your vehicle’s PCM registers the P0291 code, it means that a voltage reading came from the fuel injector circuit – for cylinder number 11’s fuel injector –...


Related questions

Q: Multiple trouble codes, no spark, no start.

You are getting codes to each and every major sensor on the engine that is needed to run your motor. You either have a major malfunction with the ECU or a problem with the harness not being wired correctly. You...

Q: My aura shakes when it starts saying "service traction" what is it?

Hello, thank you for writing in. At this point there are a lot of possible causes for your vehicle's symptoms. To gather more information, we need to start with having the vehicle scanned for diagnostic troubleshooting codes. This can be...

Q: Check engine light came on while driving

The Check Engine Light is an indicator that something is affecting your emissions in a negative way. This can be as simple as a loose gas cap, to a misfire and many things contribute to the overall emissions output. The...