Secondary air injection codes

A secondary air system uses an electric air pump to blow fresh air into the exhaust for the first minute or two after a cold start, which helps the catalytic converter warm up quickly and burn off extra fuel. A switching or check valve lets air in and keeps exhaust out the rest of the time. OBD rules require the computer to check that the air actually flows.

How these codes differ

• Flow codes (P0410 general system fault, P0411 incorrect flow, P0491 and P0492 insufficient flow on bank 1 or bank 2) mean the computer did not see the expected effect of the added air, usually on the oxygen sensors. They point to a pump that is weak or dead, a valve that does not open, or a blocked or leaking hose or passage.
• Circuit codes (for example P0412 for the switching valve circuit and P0418 for the pump relay circuit) are electrical: they point to the relay, fuse, wiring or the valve or pump coil rather than to air flow.
• Stuck codes in the P2440s (valve stuck open, pump stuck on) mean a part kept working when it should have stopped. A valve that sticks open lets moist exhaust back toward the pump.
• The test only runs on a cold start, so a repair cannot be confirmed until the engine has cooled down and the computer has run the check again.

Codes that show up together

• A pump fault or a flow code (P0411, P0491 or P0492) after the pump has already been replaced: check the valve as well. Water or exhaust condensate in the pump is a common way pumps fail, and condensate gets in through a valve that sticks and no longer closes.

Secondary air injection codes

• P2440

  Secondary air switching valve stuck open (bank 1)

  Severity: Monitor

• P2442

  Secondary air switching valve stuck open (bank 2)

  Severity: Monitor

• P0411

  Secondary air injection flow not as expected

  Severity: Monitor

• P0418

  Secondary air pump relay A circuit fault

  Severity: Inspect soon

• P2441

  Secondary air switching valve stuck closed (bank 1)

  Severity: Severity not verified

• P0410

  Secondary air injection system fault

  Severity: Monitor

• P2445

  Secondary air pump not running when commanded (bank 1)

  Severity: Monitor

• P2432

  Secondary air pressure sensor signal too low (bank 1)

  Severity: Monitor

• P0491

  Secondary air injection system is not moving enough air (bank 1)

  Severity: Severity not verified

• P1445

  On Toyota, secondary air switching valve No. 2 stuck closed (bank 2)

  Severity: Severity not verified

• P2444

  Secondary air injection pump stuck on (bank 1)

  Severity: Severity not verified

• P1444

  Secondary air switching valve No. 2 stuck open (Toyota, Lexus)

  Severity: Monitor

• P2431

  Secondary air system pressure or flow sensor reading out of range (bank 1)

  Severity: Inspect soon

• P2433

  Secondary air system pressure or flow sensor circuit reading too high (bank 1)

  Severity: Inspect soon

• P1442

  On Toyota, secondary air injection switching valve No. 2 stuck closed (bank 1)

  Severity: Severity not verified

• P2443

  Secondary air injection switching valve stuck closed, bank 2

  Severity: Severity not verified

Sources and review

1. Final Regulation Order: 13 CCR §1968.2, Malfunction and Diagnostic System Requirements (OBD II), 2004 and subsequent model-year passenger cars, light-duty trucks and medium-duty vehicles (2015 amendments) — California Air Resources Board
2. Performing troubleshooting in the secondary air system — MS Motorservice (Pierburg)

Last reviewed

October 16, 2026

Written by

Saurabh K.

Editorial review

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Technician review

Technician review pending

This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error