Secondary Air Injection System Insufficient Flow (Bank 2)
The P0492 code means the vehicle's onboard diagnostic system has detected: Secondary Air Injection System Insufficient Flow (Bank 2). This is a low severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- moderate
- Estimated cost
- $200 - $700 (parts and labor)
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Common Symptoms
- Check Engine Light on
- Failed emissions test
- Cold start emissions elevated
- Brief rough idle on cold start
Probable Causes (Ranked by Likelihood)
- Clogged secondary air passages on Bank 2 Very High
- Failed secondary air check valve on Bank 2 High
- Secondary air pump low output Moderate
- Blocked air injection port in exhaust manifold Moderate
Step-by-Step Diagnostic Procedure
-
Verify the secondary air pump runs during cold start and produces adequate airflow
-
Inspect the Bank 2 secondary air check valve for sticking or carbon blockage
-
Check the Bank 2 air injection passages in the exhaust manifold for carbon obstruction
-
Compare Bank 1 and Bank 2 secondary air system operation; if only Bank 2 is affected, the issue is isolated to that side
Common Fixes by Vehicle
What techs usually find when diagnosing P0492 on specific vehicles — tap your vehicle for the fix and the exact part:
2005-2012 Honda Pilot/Acura MDX 3.5L moderate DIY
Bank 2 air injection on Honda V6s is typically the passenger-side combo valve. Same failure mode as P0491 but on the opposite bank. Replace both valves at once since they usually fail together (Honda 36281-RYE-A01 and 36271-RYE-A01).
Labor: 2-3 hours2006-2011 Acura RDX/TSX 2.3L/2.4L easy DIY
Check the vacuum hose routing -- the Bank 2 air switch valve uses a separate vacuum signal. Cracked or swapped hoses mean the valve never opens during the cold-start test. Verify with a Mityvac hand pump: 18 in-Hg should actuate the valve audibly.
Labor: 30 min2005-2014 Subaru Tribeca/Outback H6 3.0L/3.6R moderate DIY
Failed air pump motor -- on Subaru H6 engines the pump sits in the passenger-side fender. It seizes from moisture. Replace pump assembly and install drain boot to prevent water pooling. Also inspect the check valves at the manifold for corrosion.
Labor: 2 hoursFrequently Asked Questions
What is the difference between P0491 and P0492?
P0491 indicates insufficient secondary air flow on Bank 1 of the engine, while P0492 indicates the same condition on Bank 2. On V-configuration engines, each bank has its own air injection pathway and check valve.
Can carbon buildup cause P0492?
Yes. Carbon buildup in the exhaust manifold air injection ports is a very common cause. Over time, exhaust soot and carbon accumulate in these passages, restricting airflow from the secondary air pump.
How often does the secondary air pump need replacement?
Secondary air pumps typically last 80,000 to 150,000 miles. Moisture entering the pump through cracked hoses accelerates wear. The check valve can also fail, allowing exhaust to back-flow into the pump and damage it.
Sources
This page is built from documented references. Verify against your own service info before repair work.
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