What P0411 means
P means powertrain (engine and transmission). The 0 marks a generic code defined by SAE, so the same number means the same thing across makes. The third character, 4, places it in the auxiliary emission controls subsystem; the last two digits identify the specific fault.
Secondary air injection pumps fresh air into the exhaust for a short time after a cold start, helping the catalytic converter light off sooner. It consists of an electric air pump, a relay, and one or more switching (check) valves. The engine computer runs the system and checks the result through the O2 sensors.
What “Flow” means here
The module ran its flow test on the secondary air injection system and the measured result did not match what it expected. This is a performance result, so blocked passages, stuck valves and leaks are as likely as electrical faults.
What you may notice
Symptoms depend on the vehicle and on how the module responds to the fault. Any of these can accompany P0411:
- Usually none while driving
- A loud air pump that runs briefly after cold starts, or no pump noise at all
- Readiness monitor not completing
Where to start diagnosing P0411
- Listen for the air pump running for a short period after a cold start.
- Check the pump fuse and relay.
- Inspect hoses and check valves; moisture getting past a failed check valve can seize the pump.
- Watch upstream O2 sensors go lean when the system runs on a cold start.
Clear the code only after recording freeze frame data: it shows the engine speed, load and temperature at the moment the fault set, which is often the best clue to reproducing it.
Live data to watch
These standard OBD2 values relate to P0411. Support varies by vehicle; a value your car does not report will simply be missing.
| Value | What to look for |
|---|---|
| Commanded secondary air status (PID 0x12) | Shows when the system is commanded on. |
| O2 sensor voltage (PIDs 0x14–0x1B) | Should drop lean while secondary air flows. |
Related codes
Codes from the same secondary air injection system family. If several are stored together, the shared part — wiring, a common reference voltage, or the component itself — is the place to start.
| Code | Definition |
|---|---|
| P0410 | Secondary Air Injection System |
| P0412 | Secondary Air Injection System Switching Valve "A" Circuit |
| P0413 | Secondary Air Injection System Switching Valve "A" Circuit Open |
| P0414 | Secondary Air Injection System Switching Valve "A" Circuit Shorted |
| P0415 | Secondary Air Injection System Switching Valve "B" Circuit |
| P0416 | Secondary Air Injection System Switching Valve "B" Circuit Open |
| P0417 | Secondary Air Injection System Switching Valve "B" Circuit Shorted |
| P0418 | Secondary Air Injection System Control "A" Circuit |
Further reading
Frequently Asked Questions
What does P0411 mean?
P0411 is the generic SAE J2012 code for "Secondary Air Injection System Incorrect Flow Detected". In plain terms, it means the engine computer's secondary air injection system monitor has reported "Secondary Air Injection System Incorrect Flow Detected".
Can I keep driving with P0411?
Normally drivable; it affects cold-start pollution and inspection readiness, not how the car drives.
What should I check first for P0411?
Listen for the air pump running for a short period after a cold start.
Definition source: SAE J2012 / ISO 15031-6 generic DTC definitions. This is the generic meaning that applies across makes; a manufacturer can define a code more narrowly or add its own sub-codes, so confirm against the service information for your vehicle before replacing parts. Written by the OBDAssistant engineering team — see our editorial policy.