Diagnostic article Generic OBD-II
P0AC8: Battery input two has an independent extreme-cold circuit check
Interpret the GM P0AC8 circuit-high threshold without borrowing the rationality monitor’s peer comparisons.
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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.
P0AC8 is battery temperature input two's circuit-high diagnosis. In the GM table the relevant indication is below −45°C. This is an absolute signal-limit check, not a requirement that input two disagree with all three other temperatures.
The monitor can reject one channel directly
The controller must be in run mode with its low-voltage supply in the stated range. P0A1F must be inactive. The sample rule is 30 failing observations within 40, taken at 100ms intervals.
By comparison, P0AC6 requires valid input two and a three-way disagreement pattern. Treating P0AC8 as that same comparison would add conditions that the circuit-high row does not contain.
Keep the named input in the record
Record input two's actual temperature and validity alongside its companion codes. A minimum-pack-temperature value may happen to equal it at one instant, but it does not preserve which channel generated the failure. That identity is needed when consulting the vehicle's sensor map.
The source does not establish an open connector, a failed sensor or the correct repair. It supplies no terminal or resistance-test instructions. A trained battery technician must follow the applicable circuit procedure and high-voltage isolation requirements before accessing pack components. An implausibly cold reading does not indicate that the pack is electrically discharged or safe to handle.
An input can reach its circuit limit without completing a rationality comparison.
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 236.
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
Hybrid/EV Battery Temperature Sensor B 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