P2510: ECM relay faults can mean power ends too late or too early

P2510 is an ECM power-relay performance code. In the cited Duramax implementation, the controller can detect a relay that does not switch off when commanded or one that opens too early during power-down. Those opposite timing failures share this code, so “relay stuck on” is only part of its meaning.

Two histories produce different evidence

A relay remaining on is inferred from timer values longer than would be possible if the relay opened at the end of after-run. Premature opening is indicated by a missing EEPROM write from the previous after-run. The controller is evaluating whether its shutdown sequence completed correctly, not simply checking for battery voltage at one moment.

This explains why normal operation after restarting does not exclude a power-down fault. An interrupted prior shutdown may leave diagnostic evidence even if the supply is presently restored. It also explains why a relay that switches once during inspection is not automatically proven healthy across the whole sequence.

Preserve the transition information

GM lists checking after the engine transitions from start to run or after the power-down event, with two checks per drive cycle and first-failure detection in this calibration. Event history and companion supply faults can therefore be more useful than an isolated running-voltage snapshot.

Vehicle-specific diagnosis must determine whether the relay, its control path or power continuity caused the abnormal sequence. The summary supplies no pin test or replacement instruction. Verification needs a correctly completed shutdown and subsequent monitor assessment; clearing the record without that transition does not reproduce the test.

Source and applicability

GM 2009 09OBDG01 Duramax Engine Diagnostics, only the cited ECM monitor. This historical calibration does not establish applicability to every Duramax vehicle or provide a complete service procedure.

General Motors source, physical page 24