P0490: high-pressure EGR command short to the power supply

P0490 checks the high-pressure EGR command circuit for a short-to-power category in this source. The hardware identifies the condition while H-bridge switch current exceeds 8 A during an on command.

High refers to the circuit fault category

The row does not measure excessive EGR gas flow or a valve stuck at a high opening. It evaluates the electrical drive path. Its ground-short counterpart uses the same current magnitude, so current alone is not enough to decide which short category occurred.

Monitoring requires relay supply above 11 V, no cranking, an enabled diagnostic system and determinate hardware status. The listed filter uses 240 failures among 300 samples on a 12.5 ms task, with Type A reporting.

Preserve the context for diagnosis

Record the active drive state and hardware fault classification with the failure. Comparing that event with an off-state continuity observation without considering command state can confuse separate diagnostic tests.

Verification should include normal electrical response during an eligible driven interval, using the vehicle's approved isolation procedure to establish the underlying cause. The table cannot locate a short in the harness or distinguish an actuator problem from controller electronics by code alone. It supplies no instruction to apply external power, intentionally short the circuit or bypass its protection. Exact vehicle and calibration applicability remains necessary.

Source and applicability

2025 GM 25OBDG04B diagnostic parameter tables; the cited monitor only. Vehicle, engine and calibration applicability must be confirmed separately. These tables describe detection logic, not a complete repair procedure or a component replacement verdict. gm-2025-04b, PDF page 1204.