Diagnostic article Generic OBD-II
P2188: Bank 1 rich-at-idle monitoring uses a learned negative additive correction
Understand the scoped GM P2188 additive-trim threshold and why adaptation stability matters more than an isolated live correction.
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Documented application
2025 GM 07A-1 documented monitor only. Vehicle, engine and controller calibration applicability must be established separately; no model fitment is inferred from the file.
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.
P2188 identifies the bank 1 rich-at-idle system condition. In the cited GM monitor, the assessed quantity is the additive part of long-term fuel trim in gasoline operation. The code represents a learned correction beyond its permitted boundary, rather than direct proof of a leaking injector or another particular component.
The negative boundary belongs to one trim component
The documented failure threshold is below −5.48 percent for bank 1's additive trim. The monitor requires additive adaptation to be active and applies stability conditions to the multiplicative adaptation process. Its continuation includes more than ten seconds of stability and restrictions on correction changes and comparable operating points.
A short-term fuel-trim spike is therefore not the same measurement. An unidentified combined trim value also cannot be judged against the additive boundary without confirming what the diagnostic parameter represents.
Verify readiness before judging a new reading
The row's 0.2-second evaluation is separate from the longer eligibility conditions, and reporting is two-trip. A return to an apparently normal idle display before adaptation becomes stable does not demonstrate that this specific monitor passed.
Retain the additive value, bank identity, adaptation status and operating-state history. The source supports investigating the learned rich-direction correction but provides no ranked causes, connector procedure or component replacement conclusion. The applicable controller's parameter definitions and service tests are needed to connect this scoped result with a repair.
Source and applicability
2025 GM 07A-1 documented monitor only. Vehicle, engine and controller calibration applicability must be established separately; no model fitment is inferred from the file. GM PDF, physical page 252; GM PDF, physical page 253.
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
System Too Rich at Idle Bank 1
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