P2505
ECM/PCM Power Input Signal
The ECM/PCM monitors the main switched battery feed (typically terminal 15 / ignition-switched supply via the main relay). A general fault is reported — either the input is missing entirely or it does not match the expected timing relative to ignition state. Engine may not start or stay running.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- Failed main relayCommon
- Blown fuse on the ECM power feedPossible
- Corroded connector pin at the ECMPossible
Parts involved
- Main Relay
- Power Input Wire
- ECM
P2505 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.