Technical Description of OBD-II Trouble Code
Detected Incorrect Flow in Secondary Air Injection System
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that applies to vehicles equipped with OBD-II. Although it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
The Secondary Air Injection system is an emission control system that uses an air pump (either electric or driven by the drive belt) to introduce fresh air into the exhaust manifold(s) or exhaust ports when the engine is in open loop and pre-catalytic converter when in closed loop. This helps reduce hydrocarbon emissions (HC), carbon monoxide (CO), and nitrogen oxides (NOx). The fresh air aids in converting carbon monoxide (CO) into carbon dioxide (CO2) and hydrocarbons (HC) into water vapor (H2O).
A check valve is present in the air supply line to prevent exhaust gases from flowing into the pump. The airflow may be controlled by a vacuum-controlled or electrically-controlled cutoff valve. When the powertrain control module (PCM) activates the valve, vacuum is sent to the cutoff valve to open it and allow fresh air to flow. Some systems may only have a check valve, and the flow may be regulated by an electromagnetic clutch on the air pump (similar to an A/C clutch).
During hard acceleration, the air pump is deactivated to prevent backfiring in the exhaust. To perform a self-check, the PCM activates the AIR system and directs fresh air into the exhaust system. The oxygen sensors detect this fresh air as a lean condition, causing the short-term fuel trims to adjust in a positive direction. The PCM expects to observe this adjustment within a few seconds during the self-test. If the short-term fuel trims do not increase, the PCM interprets it as a malfunction in the AIR system and records a code.
Other trouble codes related to the secondary air injection system include P0410, P0412, P0413, P0414, P0415, P0416, P0417, P0418, P0419, P041F, P044F, P0491, and P0492.
Symptoms
The symptoms of a P0411 DTC may include:
Causes
The potential causes of a P0411 code include:
Possible Solutions
If you have access to a scan tool, activate the AIR pump with the KOEO (Key on Engine Off) command. It should activate. If it does not, remove and inspect the AIR pump relay for discoloration or melting due to heat. Repair as necessary.
With the ignition on (engine off), check for battery voltage at the switched battery feed to the relay and the relay control circuit. If either of these voltages is not present, inspect the circuit for a blown fuse or an open/short in the wiring. Repair the cause of the short and retest. If both voltages are present, use a fused jumper to connect the battery feed to the AIR pump feed circuit. The pump should activate. If it does not, check for power and ground at the AIR pump when jumpered. If there is no voltage or ground, repair any open in the wiring harness. If voltage and ground are present but the pump still does not run, suspect a faulty AIR pump. If the pump activates after jumpering the AIR pump feed circuit, the problem is likely the AIR pump relay. Replace it and retest.
If the scan tool activates the AIR pump, activate the AIR pump solenoid valve with the KOER (Key on Engine Running) command and check for vacuum at the cutoff valve. There should be vacuum present to open the valve. If there is no vacuum, check the AIR pump’s vacuum solenoid valve for vacuum supply from the manifold. If there is vacuum, the vacuum solenoid is likely faulty. Replace it. If there is no vacuum at the supply to the vacuum solenoid, check for a plugged or damaged vacuum line or a plugged vacuum port. However, if there is vacuum at the cutoff valve, shut off the engine and use a vacuum pump to apply vacuum to the cutoff valve. Check if it holds vacuum and if air flows through it when vacuum is applied. If it does not hold vacuum or the valve does not allow air flow, replace the cutoff valve. If the cutoff valve functions properly, inspect the check valve for any obstruction or if it is missing. Replace as necessary.
Inspect the steel line to the exhaust catalyst as well as the exhaust ports for any damage or holes that could cause false readings.
