P0497: EVAP purge-flow assessment from tank-pressure response

P0497 is documented as a purge-flow monitor that observes tank pressure with the canister vent valve closed and the purge valve open. The table describes this as the assessment for a purge valve stuck closed.

The test requires a prepared system state

The monitor uses the difference between filtered tank pressure and starting pressure, and also references integrated purge mass during vacuum buildup. Those are responses during a controlled test, not a direct measurement proving that a valve is physically jammed.

The enable conditions include an active canister-purge diagnosis, coolant temperature above 69.75°C, ambient temperature above −7.5°C, idle operation, and essentially stationary vehicle speed. Pressure stabilization and compensation-gradient measurements precede the decision. The continuation states that the monitor runs once per trip.

How to interpret a failed or absent result

An arbitrary tank-pressure reading taken during driving does not reproduce this test. Equally, a trip without a recorded failure may not have provided the warm, stationary, stabilized conditions needed to run it.

Two-trip reporting and a one-second time column are shown, but the preparation stages have their own timing. Verification should establish the correct commanded valve states, a completed stabilization sequence, and a passing purge-flow result. The source’s pressure-sign wording is retained as a calibration matter rather than converted into an unsupported generic vacuum-test procedure.

Documentation and applicability

These details describe the monitor in GM’s 2025 25OBDG07A Part2 file. Its application-matrix filename does not match the download index, so model and engine applicability remain unresolved. Use the vehicle’s correct service information before applying these calibration details.

GM diagnostic table, PDF page 154; GM diagnostic table, PDF page 155.