P0492 OBD-II Trouble Code: Secondary Air Injection System Insufficient Flow Bank

P0492 code definition

Code P0492 indicates that there is a problem with the secondary air injection system, which plays a role in emissions control.

What the P0492 code means

With the P0492 code, it means that the car’s computer has detected a problem with the second bank in the secondary air injection system, which is used to help reduce emissions. Pressure and flow are read through voltage signals sent to the computer, and any variations significantly outside of the automaker’s normal range will trigger this code to be set. Note that the Check Engine Light may or may not illuminate in this instance.

What causes the P0492 code?

A number of potential problems can cause the P0492 code to be set in the car’s computer. These can include:

  • Faulty one-way check valve (most commonly fails in cold weather)
  • Intake leak
  • Faulty relay
  • Blown air injection pump fuse
  • Faulty secondary air pressure sensor
  • Clogged secondary air injection ports in the cylinder head
  • Vacuum leak

What are the symptoms of the P0492 code?

In many instances, the only symptom you’ll notice is the Check Engine Light coming on. However, in other instances, symptoms may include the following:

How does a mechanic diagnose the P0492 code?

First, the mechanic will check the codes stored in the computer using a handheld scanner and clear them. The mechanic will then test drive the car to verify symptoms and to see if the code will set again.

Note that in many instances, an accurate diagnosis can only be made when the engine is cold. The pump operation will need to be verified (when cold) by removing the pressure hose. It will also need to be checked for electrical problems (after being detached from the wiring harness).

The check valve will need to be inspected (when cold). This requires multiple steps, including the removal of vacuum lines, the attachment of a vacuum pump and more, depending on how the valve performs in each step.

A visual inspection for carbon buildup within the cylinder head and/or EGR valve may also be necessary. If buildup is noticed, the head will need to be cleaned out thoroughly. The mechanic should also conduct a thorough visual inspection of all secondary air injection system hoses and lines to check for tears, deterioration, cracking and other problems.

Finally, the intake will need to be checked for leaks. This is most common on the intake manifold gasket.

Common mistakes when diagnosing the P0492 code

One common mistake here is not replacing the check valve. Replacing a pump may fix the problem for a brief time, but if the check valve is faulty and is not replaced, the new pump will fail shortly after installation.

How serious is the P0492 code?

The P0492 code is relatively serious, and it should be diagnosed and repaired quickly. It will eventually have an effect on drivability, as well as on fuel economy. If it results in engine stalling, it could also pose a safety issue.

What repairs can fix the P0492 code?

Multiple repairs may be necessary to repair the P0492 code. The most common repairs are replacement of the pump and the one-way check valve. However, vacuum line leaks will also need to be repaired, and the cylinder head may need to be thoroughly cleaned of carbon build up before the code can be cleared permanently. Replacing the intake manifold gasket may also be necessary if it has developed a leak.

Additional comments for consideration regarding the P0492 code

Diagnosing the cause or causes of the P0492 code can be lengthy, requiring multiple steps and multiple codes cleared after each step.

Need help with a P0492 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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