What it means
The ECM/PCM power input signal is above the expected range. The code does not identify the cause or establish that the ECU is at risk of damage.
At a glance
- Usually lights the check-engine light
How it works
The ECM or PCM receives battery power through its supply circuits and monitors that input to ensure it stays within an expected range. P2508 means the module sees an input above that range; possible sources include excessive charging voltage or an abnormal external power connection.
Common causes
Most likely first.
- Alternator regulator overvoltage
- Improper external power source or jump-start
Symptoms
- Check-engine light
- Electrical accessories may behave erratically
- Unusually bright or flickering lights
How to diagnose it
- Save freeze-frame data and check charging-system and module-supply data to determine whether the high input occurred with the engine running or after an external power connection.
- Inspect the battery terminals, ECM/PCM power-feed wiring, and connectors for incorrect connections, damage, or signs of overheating.
- Measure battery and module supply voltage with the engine off and running, comparing results with the manufacturer's specification.
- If running voltage is high, check alternator output and regulator operation, along with charging-system grounds.
- If charging voltage is normal, inspect the module power-feed circuit for an unintended connection to a higher-voltage source.
Common fixes
- Correct an improper external power or jump-start connection and inspect affected wiring.
- Clean and secure loose or corroded battery and module power connections.
- Repair a power-feed wire shorted to a higher-voltage source.
- Repair or replace the alternator regulator if testing confirms overvoltage.
Can I keep driving?
Avoid driving if the lights are unusually bright or accessories are malfunctioning, as high supply voltage can damage electrical components. If the vehicle recently received an external power connection, check the system before continuing to drive.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.