Diagnostic article Generic OBD-II
P218A: Why bank 2 throttle stop learning can fail at several different stages
Understand P218A through closed-stop learning, sensor offset checks and the distinction between aborting and completing a test.
Read before applying this article
Documented application
2025 GM 25OBDG07A Part 2 monitor tables only; model, engine and transmission applicability are not established by the unresolved application-matrix filename join.
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.
P218A is the generic throttle actuator B idle-position-not-learned code. The GM bank 2 source describes lower mechanical-stop learning and separates several stages that can prevent a trustworthy learned offset from being established.
Reaching the stop is only the first stage
Initial learning first moves the throttle toward its closed position. A later stage presses it toward the lower stop with a defined drive effort, followed by a range check of the learned sensor voltages. A failure to reach position is therefore different from reaching it but failing the effort or sensor-offset checks.
The document supplies separate allowable voltage windows for the two position sensors at the lower stop. Those windows belong to this calibration and are not a universal throttle-cleaning or adjustment specification.
Lost eligibility is not the same as a mechanical failure
The first-learning path also recognizes a procedure aborted because an enabling condition no longer holds. The subsequent learning rows reference spring-check, power, safety and adaptation states. A failed learning status alone cannot determine whether the plate physically stuck or whether the procedure stopped for another reason.
Preserve the failed learning step, sensor values, spring-check status and reason for any abort. This evidence is more useful than repeating a reset without knowing why learning ended. The source does not authorize manually forcing the throttle against its stop or selecting a replacement body from the code alone. Use the exact vehicle's learning and diagnostic procedure to distinguish a valid failed test from an incomplete one.
Source and scope
2025 GM 25OBDG07A Part 2 monitor tables only; model, engine and transmission applicability are not established by the unresolved application-matrix filename join. These are documented monitor criteria, not a universal repair procedure. GM PDF, physical page 782 · GM PDF, physical page 783 · GM PDF, physical page 785.
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
Throttle Actuator B Control System - Idle Position Not Learned
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