P0B79: block 13 low sensing should be checked as a paired event

P0B79 is a low-range measurement code for block 13 in GM's 2010 hybrid diagnostic table. The standardized circuit M label identifies the channel family. It does not establish a particular failed cell or prove that the traction battery has reached a low state of charge.

Look for the complete pair

The monitored condition joins block 13 below 2 V with block 14 below 2 V. Preserve both readings when the problem occurs. Treating the named channel in isolation would omit a condition explicitly required by this calibration.

The table calls for fifteen failures among twenty samples, separated by 100 ms. That repeated-sample filter helps explain why an isolated fluctuation and a matured stored fault are different observations.

Determine whether retesting was eligible

RUN mode, a 9–18 V low-voltage supply and absence of P0A1F are prerequisites. The supply figures refer to the battery controller's operating environment. They must not be confused with expected high-voltage block values or used as instructions for connector testing.

A technician should use the paired readings and related codes to select the applicable sensing-circuit diagnosis. The source gives no universal replacement instruction and does not distinguish every real low-voltage condition from every inaccurate measurement. Verification should document normal relevant data during an enabled test, with physical high-voltage work performed under the vehicle's prescribed service precautions.

Source and applicability

GM 2010 10OBDG10 Hybrid Diagnostics, cited BPCM or hybrid-controller monitor only. Historical calibration values are not universal specifications; no per-code model, engine or hardware fitment has been established. GM PDF, physical page 229.