P2495: High bypass-sensor voltage does not establish full opening

P2495 concerns the upper electrical limit of the EGR cooler-bypass position signal. GM expresses this limit relative to a 5 V reference, not as a universal percentage of mechanical valve travel. A reported high circuit condition must therefore be separated from an ordinary command to move the valve toward an endpoint.

Read the raw signal before interpreting travel

The cited threshold is above 99% of the reference voltage. P2494 supervises the low end, below 1%; neither of these electrical-range checks alone measures whether exhaust gas is being cooled effectively. The meaningful evidence is the raw feedback channel and its reference context.

The test runs after cranking and requires the powertrain-relay supply above 11 V, together with its calibration enable. A supply transition outside those conditions can be informative, but it is not automatically an occurrence of this exact monitor.

Check persistence and operating eligibility

The controller uses 200 failing samples out of 250, with a 6.25 ms function task. A single high point and a completed fault therefore carry different information. Two-trip reporting is separate from this short sample-based evaluation.

A useful record keeps raw voltage, the operating state and the fault status aligned in time. Once feedback is out of range, apparent calculated position should not be accepted as independent proof of valve movement. Determining the electrical cause requires the correct circuit procedure; the high designation does not identify a failed valve assembly.

Source and applicability

2025 GM 25OBDG04A documented monitor only. Vehicle, engine and calibration applicability must be confirmed from the matching service information; no model fitment is inferred. These criteria explain controller logic, not a complete repair procedure. 25OBDG04A, PDF page 1208. 25OBDG04A, PDF page 1209.