The computer sees a problem in the system that blows air into the exhaust after a cold start. The driver may hear a loud pump or see only the engine light.
Likely causes, most common first
- Failed air pump
- Stuck check valve
- Blown fuse or faulty relay
- Cracked air hose
Parts usually involved
- Secondary air pump
- Check valve
- Relay
- Air hose
Test before you replace
Command the pump with a scan tool on a cold engine and check the hoses and check valve.
General guidance for generic OBD2 codes. Always follow the maker's procedure for the car in front of you.