Diagnostic article Generic OBD-II
P2321: A low ignition-control signal with an unresolved coil label
P2321’s useful evidence is an off-state low signal; its generic and GM coil designations must be reconciled before physical diagnosis.
Read before applying this article
Documented application
2025 GM 25OBDG07A Part 2 documented monitor only; its application-matrix filename join is unresolved. No model, engine or universal calibration applicability is inferred.
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.
P2321 appears in the generic catalog as an ignition coil H primary-control low fault. The GM row used here instead names coil F. That unresolved mapping is important: the article can explain the monitored electrical behavior without safely assigning it to a physical cylinder.
The supported electrical finding
The row describes voltage remaining low during the driver’s off state and treats it as a short-to-ground condition. It requires synchronized ignition, speed above 1,400 rpm and enough ignition-counter advancement for firing events. A 0.4-second confirmation interval and two-trip reporting are listed.
A low signal while the driver is on is not the same observation. Retaining command timing alongside the feedback avoids confusing normal switching with the off-state failure being monitored.
How to use the limitation
Resolve the exact controller and circuit designation in the vehicle’s service information before identifying a coil location. Do not silently translate H to F, or assume either letter directly gives a cylinder number. Once the channel is established, the relevant diagnostic question is why the circuit cannot achieve its expected off-state behavior. The source gives no component-isolation procedure that would justify replacing a coil, harness or module solely from this DTC.
Document scope and source
2025 GM 25OBDG07A Part 2 documented monitor only; its application-matrix filename join is unresolved. No model, engine or universal calibration applicability is inferred. These figures explain the cited controller logic, not a vehicle-specific repair instruction. Match the vehicle’s service information before applying them.
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
Ignition Coil H Primary Control 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