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P0492 – Secondary Air Injection System (Bank 2) (OBD2)

P0492 means "Secondary Air Injection System (Bank 2)". The secondary air system pumps fresh air into the exhaust for the first minute or two after a cold start, so the catalytic converter heats up faster and cold-start emissions fall.

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P0492 quick summary

Fault codeP0492
MeaningSecondary Air Injection System (Bank 2)
SystemPowertrain (Engine & Transmission)
VehiclesGeneric OBD2
SeverityLow
Can I drive?Yes. The engine runs normally, but cold-start emissions are higher and the car may fail the emissions test.
Repair cost€20 – €700

How the secondary air injection system works

An electric air pump blows air through a combination (check) valve into the exhaust ports. The extra oxygen burns the rich cold-start exhaust in the manifold, heating the catalytic converter. The check valve prevents exhaust from flowing back into the pump; it is opened by vacuum through a solenoid or by air pressure.

The control unit monitors the system with the oxygen sensors or a pressure sensor: when the pump runs, the oxygen sensor should show a lean signal. If not, it stores flow codes (P0410, P0411, P0491, P0492); other codes cover the switching valves and the pump relay.

The pump often fails because moisture or exhaust gas gets into it through a leaking check valve. Carbon can also block the air passages in the cylinder head. Faults do not affect driving, but the car will not pass an emissions inspection with the Check Engine light on.

Bank 2 is the cylinder row that does NOT contain cylinder 1, so this code only appears on V6, V8, V10, V12 and boxer engines.

On VAG vehicles (VW, Audi, Škoda, Seat, Cupra), VCDS and older VAG testers can show this code as the five-digit VAG code 16876 (P0492). Both numbers mean the same fault.

Symptoms of P0492

  • Check Engine light on
  • No pump noise after a cold start – or a loud whine/rattle from the pump
  • Usually no driving symptoms
  • Failed emissions test

Most common causes of P0492 (most likely first)

Mechanic's Pro Tip

If the pump is full of water or soot, replace the check valve along with it – a leaking check valve is usually why the pump died, and the new pump would suffer the same fate.

  1. 1.Failed secondary air pump

    Most likely

    Moisture or exhaust gas damages the motor.

  2. 2.Sticking or leaking check (combination) valve

  3. 3.Faulty pump relay, fuse or switching valve

  4. 4.Cracked air or vacuum hoses

  5. 5.Carbon-blocked air passages in the cylinder head

Step-by-step diagnostic guide

  1. 1

    Read codes

    Read all codes and note whether they concern flow, the switching valves or the relay.

  2. 2

    Listen at cold start

    Listen for the pump during the first minute after a cold start. No noise points to the pump, relay or fuse.

  3. 3

    Check relay, fuse and power

    Check the relay and fuse, and measure the supply voltage at the pump when it should run.

  4. 4

    Check valve and hoses

    Check the check valve for exhaust deposits and correct operation, and the hoses for cracks.

    Multimeter: Vacuum-operated valves should open with about 0.3–0.5 bar vacuum and seal when released.

  5. 5

    Run the system test

    Use the scan tool to run the secondary air test and watch the oxygen sensor go lean when the pump runs.

Frequently asked questions

Can I keep driving with P0492?

Yes. The engine runs normally, but cold-start emissions are higher and the car may fail the emissions test.

How much does it cost to fix P0492?

Typical repair costs are 20 € – 700 €, depending on the cause and the vehicle. The most common fixes are: failed secondary air pump; sticking or leaking check (combination) valve; faulty pump relay, fuse or switching valve. Always confirm the cause with the tests above before buying parts.

Is the secondary air system necessary?

Yes, for emissions approval. Disabling it is illegal and the Check Engine light will stay on.

Why does the pump only run for a minute?

It is only needed while the catalytic converter warms up after a cold start.

What is the difference between P0492 and similar codes?

P0492 belongs to a group of codes for the same component that differ in the type or location of the fault: P0418 – Secondary Air Injection System Relay A circuit Malfunction; P0419 – Secondary Air Injection System Relay B Circuit Malfunction; P0491 – Secondary Air Injection System (Bank 1); P2257 – Secondary Air Injection System Control A Circuit Low; P2258 – Secondary Air Injection System Control A Circuit High; P2440 – Secondary Air Injection System Switching Valve Stuck Open Bank 1. The tests on this page apply to the whole group; the type of fault tells you where to start.

Related fault codes

This guide is for information only. Working on vehicles can be dangerous — if you are unsure, have the car checked by a qualified mechanic. Values can differ between model years; always check the manufacturer's repair information.