P04E2: PCV hose pressure signal low from an open or ground short

P04E2 is the crankcase ventilation hose-connection sensor circuit-low code. The cited GM monitor uses a pressure transducer whose output represents gauge pressure between the PCV hose and atmosphere. It detects continuous open-circuit or short-to-ground behavior in that signal path.

Low circuit data is not proof of disconnected plumbing

The electrical boundary is at or below 4.3 percent of the five-volt range, associated with −5.71 kPa in this sensor calibration. That out-of-range signal must be distinguished from a valid pressure signature used by a separate hose-performance diagnostic. The label alone does not prove a PCV hose has physically come off.

The controller counts 1,280 failures among 1,600 samples at 3.125 milliseconds each. Its Type B, two-trip reporting uses repeated observations rather than one isolated pressure value.

Separate open wiring from real pressure

Preserve the raw or normalized voltage with the converted pressure and fault status. Because both values may come from the same electrical input, their apparent agreement is not independent evidence of actual crankcase vacuum.

Use the vehicle-specific sensor circuit procedure to establish why the output is held low and whether the circuit is open or grounded. The monitor does not identify the affected connector or component universally. Verification should show a completed passing circuit-low test. Checking hose attachment alone does not establish that the electrical pressure measurement is valid.

Source and applicability

This explanation is limited to the 2025 GM 25OBDG03A monitor on page 312. Its thresholds are calibration examples, not universal specifications. Confirm the vehicle, engine and controller procedure before applying them.