Genuine BMW 11-72-7-557-903 Secondary Air Injection Pump N51 SULEV

The Genuine BMW Secondary Air Injection Pump (OEM Part # 11-72-7-557-903) is a factory-original emissions control component engineered exclusively for BMW vehicles equipped with the N51 SULEV (Super Ultra Low Emission Vehicle) engine. Also referred to as the A.I.R. Pump or smog pump, this is a direct-fit OEM replacement manufactured to BMW's precise specifications.

The secondary air injection (SAI) pump plays a critical role in BMW's cold-start emissions system. During a cold start, the pump activates for approximately 60–90 seconds, forcing fresh air into the exhaust manifold. This additional oxygen helps combust residual unburned fuel in the exhaust stream, rapidly bringing the catalytic converter up to its operating temperature and dramatically reducing harmful cold-start emissions.

Common Failure Symptoms:

• Loud "jet engine" or whining noise during cold starts
• Check Engine Light with fault codes P0491 / P0492
• Failed emissions inspection or smog test
• Increased cold-start emissions

Key Features:

• 100% Genuine BMW OEM part — manufactured to factory standards
• Direct-fit replacement requiring no modifications
• Designed specifically for the N51 SULEV engine
• Restores proper emissions system function and catalytic converter warm-up performance
• Ensures continued compliance with SULEV emissions regulations

Important Note: This pump is exclusive to the N51 SULEV engine variant. Verify your engine code on the underhood emissions label before ordering. BMW's SULEV emissions warranty may cover this component for up to 15 years or 150,000 miles in qualifying states — consult a BMW dealer to confirm coverage before purchasing.

When replacing this pump, it is strongly recommended to also inspect or replace the secondary air injection check valve to prevent exhaust backflow from causing premature failure of the new pump.

OEM Part Numbers: 11-72-7-557-903 | 11 72 7 557 903 | 11727557903