P0492

What it means

P0492 means the powertrain control module has detected insufficient secondary air injection flow on bank 2 (the side of the engine opposite cylinder number one). During the cold-start monitor, the secondary air pump runs and the control unit checks the response, usually from the oxygen sensor readings or an air flow or pressure sensor. If the expected change is too small, it concludes that not enough air is reaching the exhaust on that bank and sets the code.

Symptoms

• Malfunction indicator lamp on
• Possible whistling, droning or no noise at all from the air pump on a cold start
• Failed emissions test or high hydrocarbon and carbon monoxide readings
• Slightly rough or unstable cold idle on some engines
• Often no noticeable change in normal driving

Possible causes

• Blocked, restricted or collapsed secondary air pipe or hose on bank 2, including carbon build-up at the exhaust injection portslikely
• Secondary air check valve or combination valve on bank 2 stuck closed or seized by carbon or moisturelikely
• Air pump weak, seized or water-damaged, or pump relay or fuse faultypossible
• Air switching valve, vacuum solenoid or vacuum supply fault that prevents air reaching bank 2possible
• Wiring or connector fault in the pump, valve or sensor circuitspossible
• Faulty bank 2 oxygen sensor or air flow/pressure sensor giving a false reading during the testrare
• Exhaust leak near the bank 2 sensor affecting the monitor resultrare

How to diagnose

1. Read all stored codes and freeze frame data, noting engine temperature and whether other secondary air codes (such as bank 1 or pump circuit faults) are present.
2. Visually inspect the secondary air pump, hoses, pipes, valves, wiring and connectors for damage, loose fittings, corrosion, water ingress and exhaust leaks.
3. Listen to the air pump on a cold start and check whether it runs, using a bi-directional scan tool if available to command it on.
4. Check the pump fuse and relay, and test for power, earth and control signals at the pump and valve connectors, following the manufacturer's wiring diagram.
5. Check vacuum supply and operation of the air switching valve or solenoid, where fitted, as this varies by model and engine.
6. Remove the bank 2 air hose and check by hand or with a gauge that air flows from the pump, then check the combination or check valve for free movement and blockage.
7. Inspect the bank 2 injection ports for carbon blockage as far as the engine design allows.
8. Monitor live data for the bank 2 oxygen sensor and any air flow or pressure sensor while the pump is commanded on, and compare with the manufacturer's specification.

How to fix

• Clear or replace blocked, damaged or collapsed secondary air hoses and pipes, and clean carbon from the injection ports where the design allows.
• Replace the bank 2 check valve or combination valve if it is seized, blocked or leaking.
• Replace the air pump if it is seized, weak or water-damaged, and fix the cause of any water ingress.
• Repair or replace the faulty relay, fuse, switching valve, vacuum solenoid or vacuum lines.
• Repair wiring or connector faults, then clear the code and confirm the monitor completes and passes.
• Replace a faulty oxygen sensor or flow/pressure sensor only once testing has confirmed it is at fault.

Can I keep driving?

Nearby codes

• P0491GenericAIR System Insufficient Flow Bank 1
• P0493GenericFan Overspeed