P0492Generic code

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

The P0492 code means not enough secondary air is reaching bank 2. The computer detects it because the oxygen sensor on that bank does not go lean when the pump is turned on. There are usually no driving symptoms, but the vehicle will not pass an emissions test while the code is set.

Severity
Low
Can I keep driving?
Yes, no immediate risk
Estimated cost
$100 to $1,200
Difficulty
Medium
System
Emissions Control
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

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What the P0492 code means

The secondary air system injects air into the exhaust manifold during the first minutes after a cold start. That oxygen burns the hydrocarbons coming out of the engine, which runs rich when cold, and it warms the catalytic converter up quickly. The computer checks the system by watching how the oxygen sensors react when the pump runs.

The P0492 code means that on bank 2 the sensor does not react enough. If the other bank works fine, the problem is in the valve, the hose or the passage for that bank. If both fail, it is the pump.

Moisture and carbon that clog the passages in the cylinder head are a frequent cause on engines with a lot of miles.

When only one bank fails, compare it with the other one. Swap the check valves from side to side if they are identical and see whether the code moves to the other bank. On Volkswagen and Audi V6 and V8 engines, the air passages in the cylinder head clog with carbon, and cleaning them means removing the intake manifold.

P0492 code symptoms

  • Normally no driving symptoms.
  • Check engine light on.

Likely causes of the P0492 code

  1. Stuck check valve on that bank. The most frequent cause when only one bank fails.
  2. Broken or disconnected hose. Check the clamps too.
  3. Clogged passages. Carbon blocks the air paths in the cylinder head or the manifold.
  4. Weak air pump, if both banks fail.

How to diagnose the P0492 code step by step

  1. Cold start the engine and listen for the pump.
  2. Check the valve and the hose for bank 2.
  3. Watch the upstream sensor on that bank when the pump is on. It should drop toward lean.
  4. Swap the check valves between banks if they are identical, to see whether the fault changes sides.

How to fix the P0492 code

  • Replace the valve or the hose.
  • Clean the passages.
  • Replace the pump if it is failing.
  • Clear the codes and verify.

Technical reference data

  • The system only runs after a cold start.
  • Approximate values only: check the manufacturer data for your engine.

Brand-specific notes

This is a common code on a few brands, and other makes use equivalent codes with different numbers.

P0492 on Volkswagen

Very common on Volkswagen vehicles. On V6 and V8 engines the air passages in the cylinder head clog with carbon.

P0492 on Audi

Very common on Audi vehicles. On V6 and V8 engines the air passages in the cylinder head clog with carbon.

P0492 on Porsche

Very common on Porsche vehicles.

P0492 on Toyota

Toyota uses equivalent codes with other numbers.

P0492 on Lexus

Lexus uses equivalent codes with other numbers.

Frequently asked questions about P0492

Can I drive with a P0492 code?
Yes. A P0492 code does not usually change how the vehicle drives, but you should still get it fixed.
What usually fails?
The check valve or the clogged passages. If both banks set a code, suspect the air pump.
Will I pass the emissions test?
No, not while the code is set.
How much does it cost to fix P0492?
Roughly $100 to $1,200, depending on whether it is a valve, a hose, a cleaning job that needs the manifold off, or the pump.
What does the P0492 code mean?
It is a generic OBD2 code that means the secondary air injection system is not delivering enough air to bank 2. The oxygen sensor on that bank does not respond when the pump runs.
What is the most common cause of P0492?
A stuck check valve on bank 2 when only that bank fails. Clogged passages and a broken hose are next.

Related codes

Questions about the P0492 code

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