Rick's Free Auto Repair Advice

P0411 Equinox and Terrain

P0411 on Equinox and Terrain

Diagnose and fix Equinox and TerrainP0411

P0411: Secondary Air Injection System Incorrect Air Flow Detected

Diagnostic steps

Using a scan tool with live data, monitor the Air Injection Reaction (AIR) solenoid sensor data. There are two voltages to monitor; 1-2 and 3-4. When the AIR solenoid is off, look for voltages between 2.5-2.7 volts.

Use the bi-direction scan tool to activate the AIR solenoid; voltage should rise to 3.3 volts on both sensors.

Start the AIR pump using the scan tool or using jumper wires and monitor voltages. They should be around 2.9-volts. This represents a working pump and no restrictions in the cylinder head.

If you don’t see voltage in step one check the solenoid relay on the left strut tower, fuse, or wiring harness

If the voltages don’t change when you activate the pump, check for restrictions in the cylinder head.

How the AIR system works

The secondary air injection system is used during cold starts to add oxygen to the exhaust to help burn off excess hydrocarbons introduced into the exhaust due to a cold rich mixture needed to start a cold engines.

The system uses an electric air pump to force fresh air into the exhaust stream get the catalytic converter up to temperature faster.

The system also uses a pressure sensor and shutoff/check valve. The pressure sensor is uses to monitor back-pressure. The shutoff/check valve open the passage between the pump and exhaust and the check valve prevents exhaust gas from flowing backwards into the pump.

The AIR solenoids are normally closed solenoids. When the AIR solenoids are energized, the valves open and air passes into the exhaust system. The AIR air pressure sensors operate similar to a Manifold Absolute Pressure Sensor (MAP) with different values.

Causes of Equinox and Terrain P0411

Buildup in the tube running from the shutoff valve to the cylinder head/exhaust.

GM service bulletin 18-NA-061 on P0411



GM has issued a service bulletin 18-NA-061 on P0411. GM has determined that the P0411 condition can also be caused by moisture and/or ice build up in the Secondary Air Injection system in cold climate areas.

This condition may also be caused by a by-product of using inferior fuel, creating restriction in the SAI ports in the cylinder head causing higher than expected SAI operation pressure.

If you live in a cold climate, check for signs of ice or rust int he SAI components.

GM recommends using GM UPPER ENGINE AND FUEL INJECTOR CLEANER to remove any carbon deposits.

© , 2022 Rick Muscoplat

Posted on by Rick Muscoplat


Custom Wordpress Website created by Wizzy Wig Web Design, Minneapolis MN