Diagnostic article Generic OBD-II
P219C: cylinder one can be imbalanced in either mixture direction
GM P219C can represent either lean or rich cylinder-one imbalance relative to its bank, so direction must come from diagnostic data.
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Documented application
GM 2020 20OBDG07 shared cylinder air-fuel imbalance monitor. Only the cited monitor and calibration are described; per-code vehicle and engine applicability has not been established.
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.
P219C identifies cylinder-one air-fuel imbalance. In this GM strategy, the controller evaluates an individual cylinder against the average air-fuel behavior of its bank. The code is not a direct measurement of injector flow and does not, by itself, name a defective injector.
The same code covers two directions
The shared table gives a lean-side threshold above approximately 1.18 and a rich-side threshold below approximately 0.83 for its normalized comparison. These are controller calculation limits, not fuel-trim percentages or tailpipe mixture readings. Both paths include P219C, so the stored number alone does not tell a technician which direction occurred.
Preserve the relevant cylinder and bank data before clearing memory. A bank-wide correction and one cylinder's deviation from that bank describe different patterns; a bank average can hide the individual imbalance this monitor is looking for.
Confirm that the comparison was valid
The source requires usable engine-roughness information, completed synchronization and appropriate trigger-wheel adaptation. Rough-road detection must not be active. The monitor also operates only within calibrated speed and air-charge regions and is listed as running once per driving cycle.
These prerequisites matter when judging a test after repairs. An absence of a new code during a disabled operating state is not a completed passing evaluation. The source supplies no automatic injector, ignition or mechanical repair sequence. Use the actual engine's cylinder numbering and diagnostic procedure to investigate the recorded imbalance, then verify it during an eligible operating condition.
Source and applicability
GM 2020 20OBDG07 shared cylinder air-fuel imbalance monitor. Only the cited monitor and calibration are described; per-code vehicle and engine applicability has not been established.
20OBDG07 Diagnostics, physical PDF pages 129, 130, 131, 132, 133, 134.
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 1 Air-Fuel Ratio Imbalance
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