Diagnostic article Generic OBD-II
P0975: Allison solenoid 2 open-circuit test follows a hardware fault
P0975 identifies an open shift-solenoid 2 circuit through a qualified internal driver test.
Read before applying this article
Documented application
2009 General Motors diagnostic parameter file 09OBDG01 Allison 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.
GM's Allison table uses P0975 for shift solenoid 2 control-circuit open. That is more specific than the generic shift-solenoid B range/performance label. The controller's electrical test must be understood before assuming the code proves a mechanical shift-valve defect.
A pending indication is followed by discrimination
The source first sets a pending state after a hardware-fault occurrence. Sustained hardware evidence then initiates an internal low-side-driver test. With the engine cranking or running, the follow-up result determines the open-circuit classification. The adjacent P0976 entry uses a different follow-up result for a ground-related fault.
These are controller actions, not instructions for manually opening a live solenoid circuit. They explain why a generic initial electrical indication can lead to different final codes.
Check the supply and driver prerequisites
The monitor requires powered components, a specified battery-voltage window and high-side driver 2 enabled. Related driver-supply faults must be absent. A blocked test in the presence of those faults is not equivalent to a passing solenoid circuit.
Preserve the exact code and companion driver faults for the matching transmission service procedure. The summary does not establish which physical part caused the open path. Verification should show successful completion of the qualified electrical check. A normal shift or an erased code cannot demonstrate that the controller's open-versus-ground discrimination now passes.
Source and applicability
2009 General Motors diagnostic parameter file 09OBDG01 Allison 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.
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
Shift Solenoid B Control Circuit Range/Performance
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