What it means
A fault is detected in the ECM/PCM power input signal. The code does not specify the feed circuit or whether the fault is missing power, incorrect timing, or another signal problem.
At a glance
- Usually lights the check-engine light
How it works
The ECM or PCM relies on power from the battery through fuses, relays, wiring, and connector pins to run the engine and control vehicle systems. P2505 reports a problem with the module's power-input signal, but does not identify which feed or the exact type of signal fault.
Common causes
Most likely first.
- Failed main relay
- Blown fuse on the ECM power feed
- Corroded connector pin at the ECM
Symptoms
- Check-engine light
- Intermittent stalling or no-start
- Engine may cut out unexpectedly
How to diagnose it
- Record freeze-frame data and check for related power-supply codes to see whether the fault coincided with cranking, stalling, or a no-start.
- Inspect the battery terminals, ECM/PCM connectors, and accessible power-feed wiring for looseness, corrosion, or damage.
- Check the ECM/PCM power-feed fuses and main relay, verifying that the relay switches as intended when the vehicle is powered up.
- Use the wiring diagram to check for power and ground at the module during cranking and while the fault is present.
- If feeds, grounds, fuses, and relay operation are correct, investigate the module connector pins and power-input signal circuit for an intermittent or internal fault.
Common fixes
- Clean and secure corroded battery or module connector terminals.
- Replace a blown ECM/PCM power-feed fuse after checking for a short that caused it to fail.
- Replace a failed main relay.
- Repair an open or damaged module power-feed wire or connector.
Can I keep driving?
An intermittent loss of module power can stall the engine or prevent it from restarting, so avoid driving if the vehicle is cutting out. If it runs normally, limit the trip to getting the fault checked, since an unexpected stall can create a road hazard.
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.