Severity: Fix within days. Drive with caution and watch for new symptoms.
On GM vehicles, the sensor that reports the EGR valve's position is giving a reading the computer does not expect.
Clean the EGR valve and passages, test the valve, and replace it if the position reading stays off.
Rough idle or knocking under load is common. Drivable with care.
You can drive short distances carefully; watch for worsening symptoms. Rough idle or knocking under load is common. Drivable with care.
The most common causes are: Failed EGR valve; Carbon buildup holding the valve; Failed position sensor; Damaged wiring. A scan tool and a visual check of the parts above is where a technician starts.
Clean the EGR valve and passages, test the valve, and replace it if the position reading stays off.
