Error Code P2509: What It Means & What To Do?

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The trouble code P2509 can be defined as ECM/PCM Power Input Signal Intermittent. When the ignition switch would be turned "ON", then the battery voltage would be applied from the battery to the powertrain control module (PCM)/engine control module (ECM) through the main relay. There might be some cases where the ignition switch would be turned "OFF", and then the ECM/PCM would be supplied with power through the battery power input line to control the basic operation of the automobile. The ECM/PCM would set the P2509 error code when the ECM/PCM power input would not be as per the specifications set by the manufacturer. The engine control module, powertrain control module or the transmission control module monitors this circuit depending upon the particular automobile.

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Willing to know some common symptoms of OBD Trouble Code P2509? Your wish is our demand. Have a look at them below:

Common Symptoms

• Visibility in the check engine light
• It might be very hard to start the car or sometimes failure to start
• Tachometer might start fluctuating between 500 to 700 rpm when idling cold
• Check gauges light might illuminate and voltmeter displays 11 volts or less
• Truck might cut off while driving
• Additional codes P2502 - charging system error and P2503 - charging system output low might accompany the error code P2509

If you wish to correct this fault code, then you have to follow certain steps. Correcting a problem needs your careful attention. Here are some ways with the help of which you will be able to correct the OBD Code P2509:

• Rehabilitate the defaults in the wiring harness to the battery or ECM for power supply to the ECM
• The malfunctioning PCM/ECM should be repaired or replaced as per the need
• The fuse should be restored to working order
• Recondition the non-functioning circuits
• It is necessary to perform proper service of the unsound battery cables
• Adjust the flawed battery of the car engine

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If you want to easily diagnose this fault code, then all you have to do is to follow the steps which are mentioned below:

A technician begins by hooking the vehicle to an OBD-II scanner to verify that the code is present, and check for other codes. The freeze frame data along with current data is recorded, and the codes are then cleared to see if they reoccur.

Visual inspection of the wiring and connectors to check for loose connections, corrosion, or shorts is done.

Most of the latest vehicles utilize a PCM/ECM relay in order to supply the PCM with power and ground signals. Others use a system which includes a relay as well as a fused wire that comes directly from the ignition switch or battery junction block.

This type of error code pertains to the voltage supply for the powertrain control module. Just keep in mind that the PCM and ECM are generally the same constituent.

ECM is short for "engine control module." Since the engine control module and the transmission control module are frequently integrated into a single module, the computer that controls them is referred to as the "powertrain control module." Ninety-five percent of late-model vehicles use a powertrain control module (PCM). Voltage is generally supplied to the PCM using a contact relay.

A contact relay used in automotive applications will normally used between three and five circuits for operation.

The initial circuit is constant battery voltage. This circuit is generally fused and it stays "hot" at all times. After that the next circuit is a ground circuit and it is also constant.

The third circuit will likely be an ignition power circuit which supplies a second supply of battery voltage. The contacts inside the relay are closed when the third circuit is activated, which would send power to the PCM.

A fourth (and fifth) circuit provides the PCM (and other system controllers) with an input signal that reflects relay voltage. The PCM and other controllers utilize the input voltage signal to monitor relay voltage and store a trouble code if the signal is unusual.

This error code can be successfully diagnosed by using several tools. A suitable OBD-II scanner and a digital volt/ohmmeter would be helpful in trying to perform a successful diagnosis. Gaining access to access a manufacturer's wiring schematic will also prove to be necessary to successfully diagnosing this code. You can always start with a visual inspection of all wiring as well as connectors.

Make sure to repair or restore the faulty, disconnected, shorted, or corroded wiring, connectors, and components as per the requirement.

The system should be retested after repairs are completed to ensure success. If all system wiring, connectors, and components appear to be in good working condition, then you should connect the scanner to the diagnostic connector and all the stored codes and freeze frame data should then be recorded.

This information can prove to be extremely helpful in diagnosing intermittent conditions that may have contributed to this code being stored.

Then continue by clearing the code and operating the vehicle to see if it returns. This will help to decide whether or not the malfunction is intermittent. Now once all the codes have been cleared, then the vehicle should be taken out for a test drive to see if the code returns.

If the code is not returning immediately, then it would mean that you have an intermittent condition. Intermittent conditions can prove to be quite challenging to diagnose and in extreme cases it should be allowed to worsen before a correct diagnosis can even be attempted.

Start your diagnosis with a visual inspection of the battery cables and battery cable ends. Carefully clean or replace cables and ends as per the requirement. Just make sure that the battery should be fully charged and then perform a battery load and starting/charging system test. Compare your findings with manufacturer's recommendations and then the faulty components should be replaced as per the need.

If the battery and starting/charging system are in good working condition, then the system fuses and fusible links should be tested.

The defective components should be replaced and after that retest the system. Without a constant supply of battery voltage to the PCM, your vehicle could continue to store trouble codes, stall at idle or under acceleration, or exhibit a no start condition. Then you should continue with a visual inspection of all PCM and PCM relay system circuitry.

Repair or restore any wiring, electrical connectors, or system components which appear to be defective, shorted, corroded, disconnected or faulty. If the code resets, or you are experiencing a no start condition, start by unplugging the PCM relay connector.

Examine for voltage and ground signals on the right circuits and your findings should be compared with the wiring schematic or as per the specifications set by the manufacturer.

Probe any circuits that do not coincide with the specifications set by the manufacturer with the digital volt/ohmmeter. Just be sure to disconnect the PCM and other associated control module connectors before testing individual circuits for continuity and resistance.

Repair open, disconnected, or shorted circuits as per the requirement and retest the system. If all of the circuits in the relay connector are in line with manufacturer's specs and the relay fails to provide an output signal to the PCM, then it would mean that there is some fault in the relay.

If the service engine soon lamp fails to illuminate when the key is in the key on engine off position, suspect a defective PCM relay. If all system circuits check out, and the PCM relay is providing all necessary power and ground circuits, then it would mean that the PCM is quirky.

Keep in mind that the PCM replacement would require reprogramming of one or more control modules.

Common Mistakes When Diagnosing The P2509 Code

• The mechanics might unnecessary replace the powertrain control module. Technicians might report that shortcomings in the voltage supply to the powertrain control module relay are more common in late model vehicles than in earlier automobiles which are equipped with the OBD-II systems.