P2508
ECM/PCM Power Input Signal High
Computer / power supply
Generic OBD-II
Medium
What it means
P2508 means the engine computer sees the voltage on its own power-input sense circuit reading higher than expected. Because it concerns the ECM's supply, the usual causes are an overcharging alternator, a bad ground, or corroded power connections. High supply voltage can cause stalling or hard starting, so it's worth diagnosing sooner rather than later.
Medium
Can I keep driving? Often drivable, but because this concerns the ECM's own supply voltage, it can cause stalling, hard starting, or erratic running if the charging system is overcharging.
Common symptoms
What you'll notice
- Check-engine light on
- Possible stalling, hard starting, or intermittent no-start
- Erratic running or other electrical codes setting together
- Battery/charging warning if the system is overcharging
Common causes
Most likely first
- Charging system overvoltage (faulty voltage regulator / alternator)Likely
- Poor ground or high-resistance connection at the ECM raising sensed voltageCommon
- Corroded or loose ECM power connector or power-relay terminalsCommon
- Wiring fault shorting the power-input sense circuit to a higher voltageLess often
- Faulty ECM (least likely — rule out the supply first)Less often
How to diagnose & fix
Work through it in order
- Measure battery/charging voltage with the engine running; confirm it stays within about 13.5-14.7 V.
- If overcharging, test the alternator and voltage regulator.
- Inspect and clean the ECM power and ground connections and the main power relay.
- Back-probe the ECM power-input sense circuit and compare to actual battery voltage.
- Only after supply, grounds, and wiring check out, consider the ECM. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P2508?+
It can be, but overvoltage to the ECM may cause stalling or hard starts and can stress electronics, so have the charging system checked promptly.
Can I just clear P2508?+
It returns whenever the ECM sees high supply voltage again. Fix the charging or wiring fault first, then clear.
Related codes
Often seen with P2508
Read & clear P2508 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX