Diagnostic article Generic OBD-II
P2818: GR10 torque-converter clutch remains coupled when commanded off
P2818 checks for unintended torque-converter coupling during low-speed shifts or an impending engine stall.
Read before applying this article
Documented application
2025 GM 25OBDG04B diagnostic parameter file; the cited monitor is documented, but individual vehicle, engine and calibration 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.
P2818 is the hydraulically stuck-on code for torque-converter control in this GR10 section. The controller evaluates two situations: low-speed shifts into a driving range and a separate non-garage-shift condition associated with possible engine stall. TCC command must be off for the listed assessments.
Low slip needs supporting evidence
The garage-shift branch checks absolute converter slip below 35 rpm together with engine-speed shortfall or decline and torque conditions. The other branch uses slip below 30 rpm, torque above 70 Nm and either substantial speed shortfall or rapid engine deceleration. Low slip alone is therefore not the complete test.
Fault timing is mapped to engine-speed behavior. The supporting garage-shift table ranges from 0.250 to 0.100 seconds across its listed speed-change values; additional counters and qualification apply. Reporting is Type A, one trip.
What to preserve
Retain commanded TCC state, engine and turbine speeds, torque and shift phase. Near-zero slip while lock is intentionally commanded is different from unwanted coupling with the command off. Electrical or speed-sensor faults can also prevent a valid result.
The continuation includes a branch with a placeholder-like reverse-speed value, so it is not a safe standalone drive procedure. Professional verification should follow the applicable service instructions without deliberately provoking a stall or unintended deceleration. The code does not establish a particular replacement part.
Source and application limits
This explanation covers the cited 2025 GM monitor. Confirm the vehicle and calibration in its service information before applying these limits; inclusion in this file does not establish model compatibility. GM diagnostic parameters, PDF page 2291. GM diagnostic parameters, PDF page 2292. GM diagnostic parameters, PDF page 2293. GM diagnostic parameters, PDF page 2294. GM diagnostic parameters, PDF page 2295. GM diagnostic parameters, PDF page 2296. GM diagnostic parameters, PDF page 2601.
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
Pressure Control Solenoid H Stuck On
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