Error Code P0491: What It Means & What To Do?

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The error code P0491 can be defined as Secondary Air Injection System Insufficient Flow Bank 1. This trouble code indicates that there is an issue on the side of the engine which contains cylinder #1.

This diagnostic fault code is a generic powertrain code, which means that it would apply to the OBD-II equipped vehicles. The specific repair steps can vary as it depends upon the vehicle make and model.

The ambient air is being utilized by the secondary air injection system which would inject it into the exhaust, thereby diluting the mixture as well as facilitating lower emissions production. The messages which are related to the air pressure and flow through this system are sent to the powertrain control module which would convert these messages into the voltage signals. It would make it easy for the computer to determine if there is an issue if the reading of the voltage does not match as per the manufacturer specifications. Then the PCM would tell that there is some issue and would store the P0491 trouble code.

What causes this problem with the Secondary Air Injection System Insufficient Flow Bank 1?

• Some faults in the system relay
• Leakage in the vacuum
• Issue of clogged secondary air injection parts
• Defects in the air injection pump or fuse
• There can be a bad one-way check valve in the air inlet
• Damaged wiring or connectors, or loose sensor connections
• The secondary air pressure sensor might be bad

1. Exhaust Manifold - A faulty Exhaust Manifold can be troublesome. You can always rely on us as we have best auto parts for our customers.
2. Fuel Injection System - If everything is alright with PCM, then there is surely some defect in Fuel Injection System. Get it replaced before the situation gets worse.
3. Powertrain Control Module - P0491 code can display due to some issues in the Powertrain Control Module. So, it is very important to replace the Powertrain Control Module with us at equitable prices.
4. Fuel Injector - Do you remember when was the last time you got your car Fuel Injector checked up? A defective Fuel Injector can cause a lot of issues like displaying P0491 code.
5. Engine Control Module - Are there some faults in your Engine Control Module? Don’t waste time and get them replaced or else P0491 code can turn up.

There could be countless symptoms which that would accompany with this fault code. Willing to know some common symptoms of OBD Trouble Code P0491? Your wish is our demand. Have a look at them below:

Common Symptoms

• Appearance of the check engine light
• There can be a hissing sound from the air injection system
• Issue of sluggish acceleration
• Stalling while idling or at start-up

Looking out for some ways with the help of which you can correct this fault code? Then you have arrived at the correct place. We are here to help you out, so you must check out the steps mentioned below as follows:

• You must replace the damaged wiring, connectors, or other electrical components
• The secondary air injection pump should be replaced or repaired
• Replace the pump’s one-way check valve
• If there are any damaged vacuum hoses or fittings which could be causing a vacuum leak then they should be repaired or replaced
• Make sure to replace the pump fuses
• Carefully clean the cylinder head

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It is essential to diagnose this fault code. Here are some steps which a mechanic should follow for diagnosing the problem that triggered a P0491 code to be stored:

• An OBD-II scanner should be used to verify the set code and record other relevant data
• You must verify that it isn’t an intermittent condition by clearing the codes, road testing the vehicle, and scanning the computer again to see if they return
• Inspecting the air injection pump wiring harness and other connections for damage or shorts
• Make sure to inspect the system hoses and fittings for heat damage, cracks, and other conditions that may be causing a leak
• The system fuses should then be tested
• Testing the one-way check valves to ensure that air is only able to go through in one direction
• Test the secondary air injection system pump

Common Mistakes When Diagnosing The P0491 Code

A big mistake can be made by replacing the secondary air injection system pump without actually inspecting the check valves and this would result in the pump failure. A proper diagnostic process should be carried out on all the parts

P0492 - Secondary Air Injection System Insufficient Flow Bank 2