What are the common causes of P2509?

Loose or corroded battery terminals. An intermittent ECM/PCM power feed. A blown or loose fuse in the ECM/PCM circuit. Chafed wiring in the ECM/PCM power feed.

Read ECM/PCM power input voltage while wiggling the harness. Check the battery terminals for looseness or corrosion. Test the ECM/PCM power feed and fuse for an intermittent open. Inspect the ECM/PCM harness for chafe. Repair the power feed if it drops out during the wiggle test. Clear the code and retest.

P2509

ECM/PCM Power Input Signal Intermittent

System: Speed and idle control (P code)
Lamp: Check Engine Light
Category: Powertrain - Computer and Auxiliary Controls

What it means

P2509 means ECM/PCM Power Input Signal Intermittent.

Check these first

Loose or corroded battery terminals
An intermittent ECM/PCM power feed
A blown or loose fuse in the ECM/PCM circuit
Chafed wiring in the ECM/PCM power feed

What to do next

Read ECM/PCM power input voltage while wiggling the harness
Check the battery terminals for looseness or corrosion
Test the ECM/PCM power feed and fuse for an intermittent open
Inspect the ECM/PCM harness for chafe
Repair the power feed if it drops out during the wiggle test
Clear the code and retest

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Updated

Generic SAE J2012 definition. Last updated 2026-10-10.