Diagnostic article Generic OBD-II
P0A31: Motor-B temperature plausibility uses the inverter average after six hours off
Read the GM P0A31 correlation monitor and understand why the startup thermal context matters.
Read before applying this article
Documented application
GM 2010 10OBDG10 Hybrid Diagnostics, only the cited controller and monitor. These are historical calibration examples; individual vehicle, engine and hardware applicability is not 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.
P0A31 checks the motor B temperature sensor against the average inverter-module temperature. The monitor is intended to detect an implausible relationship between otherwise in-range measurements, rather than an electrical signal pinned at an extreme.
A long off period creates the comparison opportunity
GM specifies ignition-off time of at least 360 minutes and temperatures of at least −40°C for both the motor and inverter average. A difference above 28°C is the listed fault quantity. The table also includes an 8.336-second startup delay before its qualifying sample window.
Named inverter and motor-temperature out-of-range faults must be inactive. This matters because an invalid inverter reference could otherwise make a sound motor-temperature reading appear implausible.
Use motor B data, not an unlabeled average
Capture motor B's own temperature, the relevant inverter average and off-time at the same startup. Motor A temperature or a later warm reading cannot substitute for the specified comparison. Preserve validity flags and companion codes with the values.
A failed correlation does not prove which physical sensor caused the disagreement. The source gives no connector location, resistance curve or replacement instruction. Those details require the matching motor B controller service information. High-voltage motor and inverter assemblies remain a professional service boundary; the described temperature thresholds are monitor logic, not instructions for live electrical access.
Source and applicability
GM 2010 10OBDG10 Hybrid Diagnostics, only the cited controller and monitor. These are historical calibration examples; individual vehicle, engine and hardware applicability is not established. GM PDF, page 299.
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
Drive Motor B Temperature Sensor 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