Secondary air injection system incorrect flow detected

Causes of a secondary air injection system incorrect flow detected trouble code

Secondary air injection faults are common on older vehicles equipped with a secondary air system.

Most common cause of secondary air injection system incorrect flow detected

Secondary air is added to the exhaust manifold or directly into the catalytic converter mainly to add oxygen to the exhaust to complete combustion of excess fuel and to get the catalytic converter up to full operating temperature.

The ECU commands the A.I.R. pump to run and energizes the secondary air solenoid valve to open to allow air into the exhaust. It then expects to see a leaner report from the upstream oxygen sensor to confirm that air has been added to the exhaust.

If it doesn’t see an increase in oxygen, it sets a secondary air incorrect flow trouble code.

There are two common causes of these codes

1) Failed switching valve that’s not opening
2) Failed A.I.R. pump

A failed switching valve is the most common cause of these codes

Secondary air one-way valve and solenoid

Start by check the switching valve to make sure it’s opening when commanded. It’s a solenoid valve, so make the solenoid coil isn’t shorted or open. Use a digital multimeter set to the ohms scale and check resistance on the coil. If the coil is open, you’ll get an ` or an OL or L. Replace the solenoid.

Next, check for a short to ground by touching a prove to one terminal and the other to a metal ground. You should not see continuity. Do the same on the other terminal.

Next, jumper power and ground to the solenoid to see if it’s opening and closing properly and check for carbon buildup in the valve. Replace if you find faulty movement.

If the valve is working, then the problem is most likely a bad pump.

If you have a bidirectional scan tool, you can command the A.I.R. pump on to check operation.

If you don’t have a scan tool, you’ll have to use jumper wires to add power and ground. If the A.I.R. pump doesn’t work, that must be fixed first with a new pump.

The most common code is P0411

See this post to learn what the secondary air system does and how it works.

23 Rick Muscoplat