P0492: Secondary Air Injection System Insufficient Flow, Bank 2
P0492 means the secondary air system is not pushing enough fresh air into the exhaust on bank 2, the side of the engine without cylinder 1. It is not urgent for the engine, but it turns on the check engine light and can keep the car from passing an emissions test.
You can keep driving
The data lists no change in how the car drives and no limp mode. The fault affects emissions during warm-up, so the car will likely fail an emissions test until it is repaired.
What it means
After a cold start, a secondary air pump blows fresh air into the exhaust right behind the exhaust valves. This lets leftover unburnt fuel burn off and warms up the catalytic converter faster. The engine computer monitors this air flow for each bank of cylinders. P0492 is stored when too little air reaches bank 2. On VW and Audi engines, the computer estimates the air amount from how the front oxygen sensor reacts during the cold-start phase. An Audi bulletin describes values of 0.4 to 0.7 on both banks as too little air, often caused by coked (carbon-clogged) air passages in the cylinder head. On VW and Audi V engines, each bank has its own combination valve, while both share one pump. Ford uses this code for the bank 2 secondary air monitor. GM uses P0411 instead.
Likely causes
- Secondary air passages in the cylinder head cokedVery likely
Carbon deposits narrow the passages that carry air to the exhaust valves, so not enough air gets through even when the pump runs.
- Combination valve stuck or stiffVery likely
This valve opens to let pump air into the exhaust and closes to protect the pump, and if it sticks, air flow to bank 2 drops.
- Vacuum supply or changeover valve leaking, valve closes too earlyPossible
The combination valve is opened by vacuum, so a leak can make it close before the monitoring test is finished.
- Secondary air pump weak or water in the pumpPossible
A worn or water-damaged pump cannot deliver the needed volume of air.
- Hose between pump and valve leaking or offLess likely
A leaking or disconnected hose lets air escape before it reaches the exhaust.
What you may notice
- Check engine light on
- No change in how the car drives
- Secondary air readiness not set, which shows up in an emissions test
- Possibly no pump noise after a cold start
What to check, cheapest first
- 1Start the engine cold and listen for the secondary air pump running for a short time. No noise points toward the pump or its supply. · you can do it
- 2Look at the hoses between the pump and the valves for cracks, loose ends or disconnected connections. · you can do it
- 3Read the stored codes and check for related codes such as P0491, which would point to bank 1 as well. · mechanic
- 4Check the vacuum supply and the changeover valve for leaks, and see whether the combination valve opens and holds. · mechanic
- 5Test the secondary air pump for proper operation and check for water inside it. · mechanic
- 6Inspect the air passages in the cylinder head for carbon buildup if the pump and valves test fine. · mechanic
Related codes
Frequently asked questions
Can I drive with P0492?+
Yes. The data shows no change in driving and no limp mode. The check engine light stays on and emissions during warm-up are not controlled properly, so have it repaired.
Can a loose gas cap cause P0492?+
No. The code relates to air flow in the secondary air system on bank 2. A gas cap is not among the listed causes.
Will P0492 pass an emissions test?+
Probably not. The secondary air readiness monitor is not set while the fault is present, and the check engine light is on. After the repair, a drive cycle is needed before the monitor sets again.
Can I fix P0492 myself?+
The reference marks it as not suited to DIY, with an estimated 0.5 to 4 hours of repair time depending on the cause. Checking for hose problems and pump noise is a reasonable first step, but the rest needs proper testing.
Written with the help of AI from the public OBDex definition (CC0). Each make may use the code differently. Updated: 2026-11-10