What Does the Engine Code P2500 Mean?

If your car is showing the P2500 engine code, there may be an issue with your car’s charging system or the L-Terminal of the Generator Lamp control circuit.
Written by John Pickhaver
Reviewed by Melanie Reiff
If your car is showing the P2500 engine code, there may be an issue with your car’s charging system or a problem in the L-Terminal of the Generator Lamp control circuit. 
Diagnostic trouble codes (DTCs) enable you to identify potential problems with your car’s engine. An OBD-II code reader will help you identify the code, but you’ll need to do additional work to accurately determine the root issue and complete the necessary
car repairs
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. In this article, we’ll go over the P2500 engine code: what it means, how to deal with it, and how much it costs to fix. 
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What does the engine code P2500 mean?

Definition: The powertrain control module (PCM) has detected a lower-than-expected voltage signal from the generator lamp control circuit. 
The P2500 engine code indicates a problem with your car’s charging system, which delivers the electricity that powers your car while it’s running and sustains the battery’s charge.

How much will it cost to fix?

Faulty charging systems indicate that the
alternator needs repairs
or replacement. The total cost of parts and labor can run from $400 to $1000 or more. 
If the issue lies with a blown fuse, on the other hand, professional repairs will cost much less—around $100. You may be able to fix a blown fuse yourself if you have the appropriate training and tools.

What can cause the P2500 engine code?

If your car is showing the P2500 engine code, there’s likely a problem with your car’s charging system.
Potential issues that could cause this engine code include: 
  • Faulty generator/alternator 
  • Generator harness is open or shorted 
  • Generator circuit has a poor electrical connection 
  • Faulty Engine Control Module (ECM)
  • Blown fuse

Common symptoms of the P2500 engine code

Often, when the
check engine light comes on
, you won’t notice any other discernible symptoms of the problem. When the DTC shows issues with your charging system, you’ll want to be on the lookout for the following:
  • Charging system lamp illuminated
  • A loss or decrease in power to automatic windows
  • Loss of power to the radio
  • Faint or dimmed dashboard lights
  • Loss of power to the air conditioning and heating system
  • The engine shuts off unintentionally
  • The engine has drivability problems
  • Noticeable delays during engine start

How serious is the P2500 engine code? 

Because the P2500 engine code indicates issues with your car’s charging system, you will likely encounter drivability issues if you don’t address the problem in a timely manner. 
A P2500 engine often means the alternator is not charging, which can prevent your car from starting or not turning off after starting. To avoid the possibility of getting stranded somewhere, take the car in for an inspection as soon as your schedule allows.

Can I fix the P2500 engine code myself?

It may be possible to fix the P2500 engine code yourself if the issue lies with a simple problem like a blown fuse. Even so, you should have the issue professionally diagnosed before you attempt to make any repairs. 
You won’t want to conduct repairs yourself if any of the following fixes are needed:
  • Replacing and reprogramming a faulty powertrain control module (PCM)
  • Replacing a defective alternator, starter, or battery
  • Repairing or replacing generator/alternator wiring that is loosely connected, frayed, or detached
  • Repairing poorly connected
    battery terminal ends
  • Repairing corroded battery terminal ends 
  • Repairing or replacing starter wiring that is loosely connected, frayed, or detached
  • Repairing or replacing generator/alternator fuses

How to replace a blown generator/alternator fuse

If it turns out that you just need to replace an alternator fuse, then count yourself lucky: this is the least expensive of the potential fixes listed above.  
If you have the tools and experience, you can follow these steps to replace a blown generator or alternator fuse yourself:
  • Refer to your car manual to find where your alternator fuse is located in the fuse box.
  • You’ll likely see a diagram of the fuse box where each fuse is listed. Note the position of the fuse listed as "Alternator Fuse."
  • Open your car fuse box. 
  • This can usually be done by hand but sometimes you’ll need a screwdriver (likely Phillips head) to open the top. 
  • Find the alternator fuse by referencing the diagram in your car manual. Pry the fuse out by using your fingers or a small flathead screwdriver.
  • Read the fuse rating on the side. Ensure that you replace the blown alternator fuse with another of the same rating. Replacement fuses can be found in the fuse box. 
  • Replace the alternator fuse by pushing the new one into place using your fingers. Replace the fuse box cover by snapping it into place or using a screwdriver screw.
  • Treat yourself to something nice with the money you just saved!
  • Pro Tip: Use the Index and go to “F” to quickly locate all fuse-related info.
    MORE: How to find eco-friendly cars

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