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P2500 OBD-II Trouble Code: Generator Lamp/L-Terminal Circuit Low

Check Engine Light

P2500 code definition

The P2500 diagnostic trouble code is an indication of a problem in the L-Terminal of the Generator Lamp control circuit.

Related Trouble Codes:
P2501 OBD-II Trouble Code: Generator Lamp/L-Terminal Circuit High

What the P2500 code means

The P2500 diagnostic trouble code is an indication that there may be a problem with your charging system. The battery gives power to the starter and once the engine has started up, the generator/alternator takes over. Any or all of these 3 components in a vehicle’s charging system may be faulty if the P2500 diagnostic trouble code is present. When the powertrain control module (PCM) detects a lower than normal voltage signal of the battery, starter, or generator/alternator, the generator/alternator lamp light will come on in the dashboard. The Check Engine Light may be present in addition to the generator/alternator lamp light. The powertrain control module (PCM) will then store the P2500 diagnostic trouble code.

What causes the P2500 code?

  • Faulty alternator
  • Faulty battery
  • Faulty starter
  • Generator/alternator wiring that is loosely connected, broken, or frayed
  • Battery terminal ends that are loose
  • Battery terminal ends that are corroded
  • Starter wiring that is loosely connected, broken, or frayed
  • Drained battery
  • Faulty generator/alternator fuse
  • Faulty powertrain control module (PCM) is faulty

What are the symptoms of the P2500 code?

  • A loss or decrease in power to automatic windows
  • Loss of power to the radio
  • Faint or dimmed dashboard lights
  • Loss if power to the air conditioning and heating system
  • The vehicle is hard to start
  • The vehicle may cut off after driving
  • The vehicle won’t start at all
  • There may be a bad smell coming from the battery

How does a mechanic diagnose the P2500 code?

  • Diagnostic trouble codes should be diagnosed in the order that they appear in the powertrain control module (PCM)

  • Uses an OBD-II scanner to collect all trouble codes that have been stored by the powertrain control module (PCM) as well as freeze frame data

  • Inspects the generator/alternator wiring for loose connections, broken wiring, or frayed wires

  • Checks the battery terminals for tight connections and corrosion and repairs or replaces them as necessary

  • Clears all diagnostic trouble codes from the powertrain control module (PCM) and completes a test drive to see if the P2500 trouble code comes back

  • If the P2500 diagnostic trouble code does come back, check the battery by performing a battery load test

  • Checks the power that is going to the generator/alternator

  • Checks the power going to the generator/alternator fuse

  • Clears all diagnostic trouble codes from the powertrain control module (PCM) and completes a test drive to see if the P2500 trouble code comes back

  • If the P2500 diagnostic trouble code does come back, checks the starter wiring for loose connections, broken wiring, or frayed wires and repairs or replaces them as necessary

  • Checks the operation of the alternator by performing a charging system test

  • Clears all diagnostic trouble codes from the powertrain control module (PCM) and completes a test drive to see if the P2500 trouble code comes back

  • If the P2500 diagnostic trouble code does come back, it is possible that the powertrain control module (PCM) is faulty. This is rare but it is possible.

  • If the powertrain control module (PCM) is faulty, it will need to be replaced and reprogrammed.

Common mistakes when diagnosing the P2500 code

One common mistake when diagnosing the P2500 trouble code is replacing the battery and/or starter when the generator/alternator is what needs to be replaced. Generators/alternators may be overcharging or failing to charge completely. Another common mistake when diagnosing the P2500 trouble code is when batteries, alternators, and/or starters are replaced when there are loose connections. Repairing loose connections may solve the problem without having to replace a component of the charging system.

How serious is the P2500 code?

A diagnostic trouble code is normally considered serious when it causes drivability issues or a change in performance. If the alternator is not charging, this can lead to drivability issues such as the vehicle not starting or turning off after starting. It may also be necessary to continuously jump start the car. Jump starting a vehicle continuously may cause irreparable damage to the battery and/or alternator. For these reasons the P2500 diagnostic trouble code is considered serious.

What repairs can fix the P2500 code?

Additional comments for consideration regarding the P2500 code

Most of the time, the P2500 diagnostic trouble code means that there is a problem with the generator/alternator and how it is operating. Because the battery, starter, and generator/alternator work together to start and run the car, it is always possible that there is a problem with any or all of these components.

Need help with a P2500 code?

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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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