P06A3: reference D means the fourth monitored ECM reference

P06A3 monitors 5-volt reference circuit 4 in the cited ECM implementation. A failure can involve an out-of-range level or excessive separation between filtered and unfiltered measurements. The word open in a generic title does not prove that a wire is physically disconnected.

Scaling and stability both matter

The table's reference scale assigns 100 percent to 5.5 volts. Low and high failure boundaries are 88.64 and 93.18 percent; the stability comparison uses 0.90 percentage point. Interpreting those numbers as raw volts or as percentages of a five-volt full scale would produce a different and unsupported test.

The monitor can decide from nineteen failing counts in thirty-nine or from 187.5 milliseconds continuously. A reference that looks normal when viewed later may have failed the brief variation criterion earlier.

Choose the correct circuit evidence

First establish that the code came from the ECM covered by this strategy and identify reference circuit 4 in its wiring information. The source does not map the reference to a named pressure, position or temperature sensor. A coincident sensor code may help only after that mapping is verified.

The battery-voltage prerequisites differ for engaged and non-engaged starter conditions. Verification therefore needs a completed enabled reference test, not just a single meter or scan reading with unspecified starter state. Use the applicable circuit procedure to resolve the cause; this summary does not prescribe speculative sensor replacement.

Source and applicability

Documented monitors in gm-2025-03a, model year 2025. These are module/calibration examples; vehicle, engine and transmission applicability must be confirmed independently. GM 2025-03a, page 425.