The diagnostic codeP2509 OBDII means that an intermittent power input signal has been detected in the Engine Control Module (ECM)/Powertrain Control Module (PCM). The signal is not continuous, and it is not within the parameters set by the manufacturer.
A contact relay supplies voltage to the ECM / PCM. The battery voltage, ground, and ignition circuits are located in this relay. In addition to these three circuits, the computer receives information via an output signal. If one of these signals is not within the established range, this code will be set.
Reasons for storing the P2509 OBD2 fault code are:
The battery may have defects or poor connections.
Perhaps the alternator could be overloaded.
Incorrectly adjusted or corroded system cables.
The ECM / PCM relay may be faulty.
Possible solutions of the DTC code P2509 Generic
Steps to diagnose and solve the DTC P2509 OBDII code:
Check that the battery charge level is correct. The battery should have 12.75 volts. Also, verify that it is in optimal conditions. To do this, use a voltmeter in the battery terminals after verifying that it is completely loaded. Then, start the engine. If the voltage falls below 10.5 volts, the battery possibly is defective. You must replace it.
Check all the battery cables and verify that they are correctly tightened and undamaged. Repair if necessary.
With the engine running, verify with a voltmeter that the battery terminal voltage is above 13.5 volts. If not, the regulator could be faulty. You must change the alternator.
Check that the system fuses are in good condition. You should replace any of these that have excessive consumption.