Diagnostic article Generic OBD-II
P21E0: How the cylinder 3 injector B low-circuit category differs from open load
Understand P21E0’s inactive-stage diagnostic value and the neighboring checks that help classify the fault.
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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.
P21E0 identifies cylinder 3 injector B circuit low in the generic catalog. The cited GM injector-3 row calls this the short-to-ground electrical category. Its monitored value is above 5 V while the power stage is not active.
The source value is not an external pin instruction
The internal output-voltage observation must be read with the stage state and diagnostic category. The summary does not specify a connector measurement point or explain the full driver topology, so it would be incorrect to convert that value into a universal external short-circuit test.
The same channel has a separate open-load check using a bounded inactive-stage voltage window and a high-circuit check using active-stage current. P21E0 is therefore a distinct classification rather than a generic indication that any injector test failed.
Conditions determine whether a retest is meaningful
The row lists three events, engine speed of at least 80 rpm and battery supply between the specified 10.9–25.5 V boundaries. Additional inhibition rules are referenced. An observation taken with no eligible events cannot demonstrate a pass.
Confirm the engine's injector B configuration before locating the circuit fault. Matching the document's channel number to the generic cylinder number does not provide a physical connector location. The code concerns electrical behavior and does not establish fuel delivery, nozzle condition or which component should be replaced without further circuit evidence.
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 556.
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
Cylinder 3 Injector B Circuit Low
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