Diagnostic article Generic OBD-II
P0B4D: Block-four high sensing is a single-channel upper-limit test
Read the GM P0B4D voltage-sense monitor without importing the neighboring low-limit test’s paired condition.
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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.
P0B4D is the upper-limit diagnostic for block-four voltage sensing. The cited GM threshold is a block-four indication above 23V. This entry evaluates the named channel directly; it does not require block five to be high at the same time.
The opposite fault has different logic
The adjacent P0B4C low-limit monitor uses a pair of low readings. Copying that pair requirement into P0B4D would change the documented high-limit test. Here the prerequisites are battery-controller run mode, an accepted low-voltage supply and no controller-performance fault.
The failure decision counts 15 qualifying samples within 20 at 100ms intervals. An isolated high sample may be worth retaining, but it is not the entire controller decision.
Distinguish a sensing limit from overcharge proof
Save the exact block-four reading, its status, the pack reference and other voltage-sensing codes. The upper-limit code does not independently identify a charging-control failure or prove a damaged physical block. Its physical location also cannot be inferred from the number alone.
The correct battery diagram and service tests are needed before choosing a repair. A trained high-voltage technician must use prescribed isolation and verification for any pack access. Do not increase battery voltage to reproduce this calibration threshold, and do not treat the scanner's reading as a direct safety measurement.
The dedicated pack reading and this block input are different measurements.
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 224.
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 Voltage Sense D 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