P0492: Secondary Air Injection System Insufficient Flow (Bank 2)

What it means

AIR system flow on bank 2 is below threshold during the cold-start self-test — typically a clogged check valve, leaking hose, or weak air pump.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

The secondary air injection system sends fresh air into the exhaust during cold starts to reduce emissions as the engine and catalyst warm up. The control module checks for expected airflow on Bank 2 during the cold-start self-test. P0492 sets when Bank 2 receives less flow than expected, which can result from a restricted passage, leak, weak pump, or control fault.

Common causes

Most likely first.

1. Restricted or carbon-clogged air passage or check valve
2. Weak or failed secondary air pump
3. Leaking, disconnected, or split air hose
4. Faulty air control valve or relay

Symptoms

• Check engine light on
• Rough running or misfire shortly after a cold start
• Increased exhaust emissions
• Failed emissions inspection

How to diagnose it

1. Review freeze-frame data and related codes to confirm the fault occurred during a cold-start test and determine whether other secondary-air faults are present.
2. Inspect Bank 2’s secondary-air hose, check valve, and air passage for disconnection, splits, carbon restriction, or exhaust soot.
3. Check whether the secondary-air pump runs during the test; if it does not, inspect its electrical supply, relay, and control circuit.
4. Test Bank 2 airflow and check-valve operation using the manufacturer’s procedure, comparing it with the expected system response.
5. Repair the confirmed Bank 2 restriction or leak, or the failed pump, valve, or relay, then verify flow during a cold start.

Common fixes

• Reconnect or replace a leaking, split, or disconnected hose supplying Bank 2.
• Clear a carbon-restricted Bank 2 check valve or air passage if it is serviceable.
• Replace a weak or failed secondary-air pump after confirming its electrical supply and control.
• Replace a faulty air control valve or relay if testing shows it is preventing Bank 2 airflow.

Can I keep driving?

You can generally drive if the engine runs normally, though cold-start roughness or misfire and increased emissions may occur. Repair it before an emissions inspection, and avoid repeated short trips if they worsen cold-start running.