P2508
ECM/PCM Power Input Signal High
The ECM/PCM switched-battery input reads above the upper threshold. Most often caused by a charging system overvoltage (failed alternator regulator) or wrong jump-start procedure. Sustained high voltage risks damaging ECU electronics.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- Alternator regulator overvoltageCommon
- Improper external power source or jump-startPossible
Parts involved
- Alternator Regulator
- Power Distribution
P2508 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.