What it means
The sense (feedback) line that lets the ECM verify the main power relay has actually closed shows intermittent dropouts. The ECM expects to see battery voltage on this line whenever the relay is energised — short losses suggest aged contacts, vibration or chafed wiring.
At a glance
- Usually lights the check-engine light
How it works
The ECM/PCM monitors a feedback line to confirm that its main power relay has closed and is supplying power. P2511 sets when that sense line intermittently loses its expected voltage while the relay is energised, often because of worn relay contacts or a vibration-sensitive wire or connector.
Common causes
Most likely first.
- Aged main relay contacts
- Chafed sense wire shorting intermittently
- Connector with intermittent contact under vibration
Symptoms
- Check-engine light
- Intermittent stalling or no-start
- Electrical functions may cut out briefly
How to diagnose it
- Check freeze-frame data and live relay status for brief sense-voltage dropouts, especially around the reported stall or electrical interruption.
- Inspect the main power relay and its socket for loose fit, corrosion, heat damage, or worn contacts.
- Inspect the relay sense wire and connectors for chafing, pin damage, or movement that could interrupt contact.
- Monitor sense-line voltage while gently moving the accessible harness and relay connector to try to reproduce the dropout.
- Check relay output and sense-circuit continuity against the wiring diagram and manufacturer's specification.
Common fixes
- Secure a loose relay or connector and clean corroded terminals.
- Repair a chafed sense wire or a connector that loses contact under vibration.
- Replace the main power relay if its contacts cause intermittent output loss.
- Repair a damaged relay socket or terminal that fails the continuity check.
Can I keep driving?
The intermittent relay signal can precede an unexpected stall or no-start, so avoid driving in situations where a sudden loss of power would be dangerous. If electrical functions cut out or the engine stalls, pull over safely and have the fault addressed.
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.