Diagnostic article Generic OBD-II
P2505: Interrupted permanent ECM supply affects engine-off timing
Understand the permanent battery-supply interruption behind this GM P2505 monitor and why it differs from a general low-voltage code.
Read before applying this article
Documented application
GM 2015 15OBDG04 ECM Summary Tables, permanent supply interruption monitor on physical page 247. The source does not establish a particular vehicle, engine or wiring layout for this code.
The code alone does not identify a failed part or establish that a vehicle is safe to drive. Confirm the vehicle, reporting module and applicable service procedure.
The cited GM P2505 monitor detects an interruption in the permanent battery-voltage supply to the ECM's engine-off-time circuit. Its focus is continuity of that supply path. This is narrower than saying the entire vehicle battery is weak or that every ECM power input failed.
Why key-off history matters
The circuit supports the controller's engine-off timing information. A supply interruption between operating periods can therefore matter even when the engine later starts and charging voltage looks normal. A current running-voltage reading does not reconstruct whether the permanent feed remained available during the preceding interval.
The table identifies interruption through an open circuit as the monitored event. It does not provide a low-voltage threshold, identify a particular fuse or determine whether the interruption was intentional. A documented battery disconnect and an unexplained recurring interruption should be distinguished in the diagnostic history rather than automatically treated as the same repair problem.
When the controller checks
This implementation enables the check with ignition on and evaluates it once per driving cycle at a 0.01-second rate when its basic conditions are met. It uses event-based failure recognition rather than publishing a duration for how long the battery must be disconnected.
Preserve timing-related companion faults and recent power-service history before clearing the record. Verification should establish continuity through the relevant off/on sequence and a completed monitor result using vehicle-specific service information. The code alone does not justify replacing the ECM, and the source summary does not supply wiring locations or a complete power-distribution test.
Source and applicability
GM 2015 15OBDG04 ECM Summary Tables, permanent supply interruption monitor on physical page 247. The source does not establish a particular vehicle, engine or wiring layout for this code.
Article source documents
Source checks describe how the text was prepared; they do not certify a diagnosis or confirm compatibility with every vehicle using this code.
Original code reference
Dictionary definition
ECM/PCM Power Input Signal
This definition retains its original catalog scope. The article above is limited to its explicitly documented application.
Reference scope
Generic OBD-II definition.
A manufacturer label does not establish the model, year, engine or module to which a diagnosis applies. Read the safety and diagnostic limits.
Definition source
- DTC Database: pinned community code definitions
Source checked · MIT