Diagnostic article Generic OBD-II
P0990: Pressure switch E fails to confirm pressurization
P0990 checks whether switch E reaches the expected pressurized state after a calibrated hydraulic delay.
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Documented application
2009 General Motors diagnostic parameter file 09OBDG03 TRANS Diagnostics.pdf. Section-specific modules and calibrations; no per-code model or engine applicability 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.
P0990 is the pressurized-state counterpart of the switch E check in GM's group 03 transmission table. The controller expects the switch to report pressure when the CBR1/C456 hydraulic condition reaches the specified high level.
The continuation page supplies the actual decision
The first page lists pressure at or above 700 kPa. The following page explains that a table-based hydraulic delay must expire before switch state is judged. If the switch does not indicate pressurized afterward, the controller increments a failure counter; the listed threshold is 15 failing counts.
Reading only the generic high-circuit title would miss both the hydraulic expectation and the delay. A switch state observed during an unfinished pressure transition cannot be treated as the completed diagnostic result.
Determine whether the state or its report is wrong
The monitor requires suitable fluid temperature, voltage and engine speed and excludes specified temperature, solenoid and range faults. Those prerequisites need to be restored before lack of a returning code can count as verification.
Preserve the expected pressure state, switch indication and related faults. Follow the matching transmission procedure to separate hydraulic behavior from switch or circuit reporting. P0990 alone does not choose a replacement part. Verification should demonstrate the correct pressurized indication after the prescribed delay and successful monitoring, not merely an empty code list immediately after clearing.
Source and applicability
2009 General Motors diagnostic parameter file 09OBDG03 TRANS Diagnostics.pdf. Section-specific modules and calibrations; no per-code model or engine applicability established. This explanation describes the documented monitor, not a universal repair procedure.
GM diagnostic parameters, PDF page 41 · GM diagnostic parameters, PDF page 42.
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
Transmission Fluid Pressure Sensor/Switch E Circuit High
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