P2509 Code: PCM Power Input Signal Intermittent

On-board diagnostic (OBD) codes are designed to help you or your mechanic identify potential problems in your vehicle. They can be retrieved with a scan tool, but knowing what they mean is another thing.

This article may give you a better idea of how a P2509 error may affect your vehicle. Learn about the code’s definition, triggers, and symptoms with the help of this informative guide.

What Does the P2509 Code Mean?

Diagnostic trouble code (DTC) P2509 stands for “PCM Power Input Signal Intermittent.” This code is logged when the powertrain control module (PCM) loses its power supply. Like any electrical device, the PCM needs a complete circuit with power and ground. The PCM relies on a constant power supply from the battery. If this supply is interrupted, it will log error code P2509.

The PCM should always be supplied with a stable current to operate smoothly, regardless of whether the ignition is switched on or off. It receives a constant voltage from the batteries through unswitched battery wires that are directly connected to the positive battery post. The PCM also receives switched battery input through the vehicle ignition switch wire when the vehicle is turned on.

When the PCM’s voltage supply is interrupted, the module will log error code P2509.

You can learn more about how PCM voltage disruption can cause OBD codes like P2509 to appear in our discussion about ECM/PCM power feeds.

Note: The definition of code P2509 may be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

What are the Possible Causes of the P2509 Code?

P2509 is a generic code, so it can have many causes. Here are the most common:

• Loose or corroded battery cables or terminals
• Low battery voltage
• Defective battery
• Wiring issue with the PCM’s circuit
• Defective PCM
• Leaking diode

What are the Common Symptoms of the P2509 Code?

You may notice the following symptoms if your vehicle has logged the code P2509:

• Illuminated check engine light
• Vehicle does not start
• Engine may stall
• Depending on the severity, other DTCs may also be stored

How to Diagnose the P2509 Code

Diagnosing code P2509 can be hard because it shares similar triggers and symptoms with other DTCs. However, this does not mean it shares a universal fix. Vehicles are built differently depending on the manufacturer, so diagnostic procedures may vary.

Always refer to repair and diagnostic information specific to your vehicle when attempting diagnosis. Alternatively, let a technician troubleshoot your vehicle if you’re not confident in your auto repair skills.

How to Fix the P2509 Code

Code P2509 may be set in vehicles of varying makes and models. It may also share similar triggers and symptoms with other DTCs. However, sharing similar symptoms does not mean a single solution will work on every vehicle with the same logged code.

Always refer to the factory repair information of your vehicle before DIY-ing any repairs. If you don’t have the required tools or know-how to attempt repairs for this code, you can have a mechanic do it for you. Just bring your vehicle to an auto repair shop for the appropriate diagnosis and fix.

ECM / PCM Power Feeds

The ECM/PCM on every modern vehicle has multiple power and ground feeds. There is “Keep Alive Power” to prevent the loss of Adaptive Memory Tables, and there are pins that are only powered when the key is on. Those feeds are usually, but not always, delivered through a dedicated relay and, on some systems, that same switched power will feed the solenoids controlled by the ECM/PCM.

If one of the power feeds to the ECM/PCM is intermittently lost, it poses a significant problem because every power feed is there for a reason. Sometimes if one of the grounds is lost it can cause P2509 or similar codes.

Where To Buy Parts for the P2509 Code

You’ll likely need a new battery if you’re looking to solve the P2509 trouble code. Good thing you can buy one with just a few clicks here at CarParts.com! We can ship that new battery to your door in as fast as two business days if you order by 12 PM ET.

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Products Mentioned in this Guide

Battery Engine Control Module