P0492
Secondary Air Injection System Insufficient Flow (Bank 2)
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The P0492 code is the bank 2 counterpart to P0491, indicating insufficient airflow from the secondary air injection (SAI) system into the exhaust on bank 2 (the side opposite cylinder 1 on a V-configuration engine). The SAI system injects fresh air into the exhaust during cold starts to help the catalytic converter reach operating temperature faster and reduce cold-start emissions.
If you see both P0491 and P0492 together, the issue is likely the shared air pump or a common vacuum supply — since both banks would be affected by a single pump failure. If only P0492 is present, the problem is more likely isolated to the bank 2 check valve, diverter valve, or the air passages on that side of the engine.
This code only applies to vehicles equipped with a secondary air injection system, which is common on many V6 and V8 engines but not found on all vehicles. The system only operates for the first minute or two after a cold start, so it won't affect your driving experience once the engine is warm. However, the code will cause an emissions test failure. If you hear abnormal sounds from the air pump during cold starts, address the issue promptly to prevent further damage to the pump.
Severity
Symptoms
- •Check Engine light is on
- •Unusual noise from the air pump (whining, grinding, or hissing)
- •Rough or unstable idle during cold starts
- •Sluggish performance during engine warmup
- •Vehicle fails emissions inspection
Likely Causes
The check valve on the bank 2 air injection line fails and allows hot exhaust gases to flow backward, damaging the pump and blocking air delivery.
The air pump has failed or is producing insufficient airflow due to internal damage, often from exhaust backflow through a bad check valve.
Vacuum hoses controlling the bank 2 air diverter or shut-off valve have cracked, rotted, or disconnected, preventing proper air routing.
Carbon deposits in the cylinder head passages on bank 2 restrict secondary air from reaching the exhaust, causing insufficient flow.
The valve that routes secondary air to bank 2 is stuck, clogged, or failed, preventing air delivery to that side of the exhaust.
Estimated Cost
Professional Repair
Includes parts + labor
Common Fixes
- Replace the one-way check valve on the bank 2 air injection line
- Replace the secondary air injection pump
- Repair or replace deteriorated vacuum hoses to the air switching valves
- Clean carbon buildup from the bank 2 air injection ports