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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
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