P2509 OBD-II Trouble Code: ECM/PCM Power Input Signal Intermittent

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P2509 code definition

The P2509 diagnostic trouble code is an indication that the ECM/PCM power input signal is having an intermittent problem.

Related Trouble Codes:

What the P2509 code means

The powertrain control module (PCM/ECM) receives information from several circuits. A contact relay is used to supply voltage to the PCM. The battery voltage circuit, ground circuit, and ignition power circuit are located on the contact relay. In addition to these three circuits on the contact relay, the PCM receives information through an output signal. If the voltage of these signals does not remain within the specifications that have been predetermined by the manufacturer, the PCM will store the P2509 diagnostic trouble code and the Check Engine Light will come on.

What causes the P2509 code?

  • Blown fuse
  • Faulty fusible link
  • Faulty circuits
  • Faulty battery
  • Faulty battery cables
  • Faulty PCM relay
  • Faulty powertrain control module

What are the symptoms of the P2509 code?

  • Check Engine Light on
  • Engine won’t start
  • Engine won’t crank
  • Engine shuts down
  • Check Engine Light faulty

How does a mechanic diagnose the P2509 code?

  • Diagnostic trouble codes should be diagnosed in the order that they appear in the PCM.

  • Use an OBD-II scanner to collect all trouble codes that have been stored by the PCM as well as freeze frame data.

  • Inspect the PCM wiring for damage, frays, breaks, and shorts.

  • If the PCM wiring has damage, frays, breaks, or shorts, repair or replace them.

  • Inspect the battery cables for loose connections, broken terminals, and corrosion.

  • Repair or replace battery cables as necessary.

  • Clear all diagnostic trouble codes from the PCM and operate the vehicle or complete a test drive to see if the P2509 diagnostic trouble code comes back.

  • If the P2509 diagnostic trouble code does come back, test the PCM relay to see if it is working properly.

  • Inspect and test the fuse and fusible link.

  • Clear all diagnostic trouble codes from the PCM and operate the vehicle or complete a test drive to see if the P2509 diagnostic trouble code comes back.

  • If the P2509 diagnostic trouble code does come back, test the electrical circuitry of the relay and fuse system.

  • Clear all diagnostic trouble codes from the PCM and operate the vehicle or complete a test drive to see if the P2509 diagnostic trouble code comes back.

  • If the P2509 diagnostic trouble code does come back, inspect the battery and charging system for proper operation.

  • Repair or replace the battery and/or charging system components as necessary.

  • Clear all diagnostic trouble codes from the PCM and operate the vehicle or complete a test drive to see if the P2509 diagnostic trouble code comes back.

  • If the P2509 diagnostic trouble code does come back, place the key in the ignition and turn it to the on position. If the Check Engine Light does not come on, a faulty relay is possible.

  • If the relay is not faulty, replacing and reprogramming the PCM may be necessary.

Common mistakes when diagnosing the P2509 code

It is common for misdiagnosis to occur when components other than the PCM are overlooked. Often the PCM does not need to be replaced and reprogrammed and repairing or replacing relay fuses, other fuses, battery wiring, or the battery itself can resolve the P2509 diagnostic trouble code. Replacing and repairing these components is much more cost effective than replacing and reprogramming the PCM.

How serious is the P2509 code?

A diagnostic trouble code is normally considered serious when it causes drivability issues or a change in performance. When the P2509 diagnostic trouble code is stored in the PCM the car will experience drivability and performance issues in that it may not start or the engine will completely shut down. For this reason, this diagnostic trouble code is considered serious and should be diagnosed and repaired as soon as possible.

What repairs can fix the P2509 code?

Additional comments for consideration regarding the P2509 code

The P2509 diagnostic trouble code is not always an indication that the powertrain control module (ECM/PCM) needs to be replaced and reprogrammed. It is common for low battery voltage or a bad relay fuse to be the cause of this trouble code. This should not be overlooked during diagnosis of the P2509 trouble code.

Need help with a P2509 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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