P0A05: power-electronics coolant-pump driver has an open-circuit result

P0A05 in the cited 2009 GM two-mode hybrid table is an open-circuit diagnosis for the power-electronics coolant-loop pump power stage. The monitor uses an internal electrical voltage check in the driver circuitry.

Electrical continuity and cooling performance differ

The code does not directly measure coolant circulation or establish a trapped-air or blocked-hose condition. Those can matter to cooling, but this row's evidence concerns the pump's electrical power stage. A coolant-flow complaint should not be substituted for the actual circuit result.

The adjacent P0A06 branch identifies a short-to-ground condition. Retaining the precise code distinguishes an open-circuit investigation from the neighboring electrical polarity.

The published check is qualified

The table requires engine speed above zero and battery voltage within its stated operating band. It evaluates the condition over four seconds and lists a two-trip reporting classification. A pump observed with the controller asleep or the engine stationary is not automatically being tested under the same conditions.

The internal criterion is identified as an integrated-circuit decision. The document supplies no universal external voltage threshold or connector pinout that would independently prove the failure.

A qualified hybrid technician should correlate the stored driver result with the applicable pump circuit and system state. Do not bridge the power stage or work on high-voltage-associated equipment from this summary alone. Verification needs a valid electrical monitor result and any separate cooling checks required by the full service procedure.

Application limits

2009 General Motors diagnostic parameter file 09OBDG13 2-Mode Hybrid Diagnostics.pdf. Section-specific modules and calibrations; no per-code model or engine applicability established.

Source

09OBDG13 2-Mode Hybrid Diagnostics — 2009 Diagnostic Parameters, physical PDF pages 16.