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P2509 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.

Definition

“PCM Power Input Signal Intermittent.” This code is logged when the powertrain control module (PCM) loses its power supply.

Meaning

The powertrain control module (PCM/ECM) receives information from circuits used to supply voltage to the PCM. The voltage of these signals needs to remain within manufacturer specifications 

If the PCM has trouble receiving power, it will fire out the P2509 error code which will trigger the Check Engine Light.

Causes

Blown Fuse

You can remove the fuse box cover and replace the fuse in question.

Faulty Fusible Link

A fusible link is a piece of wire that is designed to melt and cease conducting electricity, once its current carrying capacity is exceeded.

Faulty Circuits

This could be an open or short in the circuit or one of its wires.

Faulty Battery

If the vehicle fails to start the voltage may be low and could indicate a faulty battery.

Faulty Battery Cables

The car’s battery cables could be nicked, frayed, etc.

Faulty PCM Relay

The PCM relay controls the power and signals to the vehicle. Most of the time when the PCM relay is not functioning properly the vehicle will not start.

Faulty Power Control Module

If your vehicle's powertrain control module (PCM) has gone bad, you'll likely need to replace the unit. 

Symptoms

Check Engine Light on

The check engine light is the automotive equivalent of a doctor doing an examination. You’ll need a tool to figure out what the problem is and try to get it fixed..

Engine Won’t Start

When your car won’t start, it’s never a good thing. It can leave you stranded in the worst places, and it can eat up your time.

Engine Won’t Crank

This might happen with a faulty PCM, because the module can no longer communicate with the engine properly.

Engine Shuts Down

Warning messages indicate a problem with the Powertrain system, such as a failed spark plug, faulty fuel injector, or dirty air filter.

Check Engine Light Faulty

The check engine light is designed to alert you that something is wrong with your car. The light isn’t immune from faults 

Diagnosis

  • Use an OBDII scanner to collect all PCM trouble codes.
  • Inspect all PCM wiring for damage, frays, breaks, etc. Repair or replace damaged items.
  • Check the battery cables first for broken terminals and corrosion. Repair or replace as needed.
  • Clear all trouble codes from the PCM and complete a test drive. If the P2509 code comes back, test the PCM relay next. 
  • Check out the fuse and fusible link. Make any repairs you need to. Clear all trouble codes and complete a test drive. If the code comes back, test the relay and fuse system.
  • Clear all trouble codes and complete a test drive. If the code comes back, check out the battery and charging cables. Repair or replace any bad components.
  • Clear all trouble codes and complete a test drive. If the P2509 code comes back, test for a faulty relay. 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

The code P2509 is thrown off if the engine control module (ECM) detects Misfire or a Multiple Spark-Per-Cylinder condition. A misfiring cylinder can be caused by an air leak, a vacuum leak or even fuel delivery issues.

How serious is this?

The P2509 Code is normally considered to be serious because it’ll eventually lead to more serious problems such as engine starts. The problem needs to be fixed sooner than later.

What repairs can fix the code?

Repair or replace any blown fuses, fusible links and circuits, faulty battery and/or battery cables and PCM relays. A PCM replacement or reprogramming is possible.

Related codes

  • P2505: ECM/PCM Power Input Signal
  • P2506: ECM/PCM Power Input Signal Range/Performance
  • P2507: ECM/PCM Power Input Signal Low
  • P2508: ECM/PCM Power Input Signal High

Conclusion

By now you should have a better understanding of what the P2509 OBDII Code is and how to diagnose and repair the problem. Be aware that the problem will not fix itself. You’ll need to get your vehicle repaired as soon as possible as the problem involves engine starting issues.