|Trouble Code||Fault Location||Probable Cause|
|P0411||Secondary air injection (AIR) system -incorrect flow detected||AIR pump, AIR valve, AIR hose(s)|
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What Does Code P0411 Mean?
The secondary air injection (AIR) system aids in reducing hydrocarbon (raw fuel) tailpipe emissions during a cold start. An electric air pump draws fresh air and pumps it into the exhaust in order to accelerate catalytic converter operation. A secondary air injection pressure sensor is used by the Powertrain Control Module or PCM to monitor the air flow from the air injection pump. The PCM supplies 5 volts to power the sensor and another 5 volts as a reference or signal while finally supplying the much needed ground on the third circuit. The sensor returns a certain amount of the reference voltage based upon the amount of pressure changes within the exhaust system.
Code P0411 will set when the predicted system pressure and actual system pressure is above a predetermined amount for a certain amount of time (for example; above .4 volts for 22 seconds). This amount is set by the manufacturer.
What are the common causes of code P0411 ?
- High resistance in connections/relay contacts to A.I.R. Pump Relay – likely
- Failed A.I.R. Pump – possible
- Failed A.I.R. System Pressure Sensor or BARO Sensor – possible
- Failed PCM – unlikely
What are the symptoms of code P0411 ?
- Malfunction Indicator Light “ON”
- Possibly Reduced Engine Power, depending upon the failure and how long failure has been occurring
- Possible noises from the A.I.R. pump, depending upon the failure and how long failure has been occurring
How do you troubleshoot code P0411 ?
First, take a look and see if there are any technical service bulletins (TSB) for your particular vehicle. There may be an update, or known fix put out by the manufacturer that can save you from wasting time and money.
Next, see if there are any other diagnostic fault codes. Diagnose current faults first, in the order in which they are stored. Misdiagnosis occurs when this code is diagnosed when it is a stored code, especially while other codes are active. Also, check for active Secondary A.I.R. Pump or Pump Relay fault codes. If these codes are present, diagnose them before attempting to diagnose the P0411.
If P0411 is the only active fault code present, and there are no updates/TSBs for your particular vehicle, then the next step is to locate A.I.R. Pump Relay on your particular vehicle. Once located, visually inspect the connections and wiring. Look for burn spots or melted plastic. Pull the connectors apart and carefully inspect the terminals (the metal parts) inside the connectors. See if they look corroded, burnt or possibly green in color versus the normal metal color you are probably used to seeing. You can get some Electrical Contact cleaner at any parts store if cleaning of the terminals is needed and a light plastic bristle brush to clean them with. Afterwards let them air dry, get some dielectric grease (same stuff they use for light bulb sockets and spark plug wires) and put some where the terminals come into contact.
While the relay is removed from its socket, momentarily bypass the A.I.R. Pump Relay by taking a jumper wire and plugging one end into pin 30 and one into pin 87. The pump should run. If it does not, the A.I.R. Pump will need to be replaced.
If the pump runs, find another relay identical to the one removed from the A.I.R. Pump Relay socket. Plug the new relay into the socket for the A.I.R. Pump Relay.
If you have a scan tool, clear the diagnostic trouble codes from memory, and see if this code returns. If it does not, then the connections/relay were most likely your problem, which is the most common issue.
If the P0411 code does return, we will need to test the sensor and its associated circuits. Typically, there are 3 wires at the A.I.R. System Pressure Sensor.
Disconnect the harness going to the A.I.R. System Pressure Sensor. The sensor is usually part of the Secondary Air Check Valve. For this code, the easiest thing to do is take a fused jumper wire (that’s a jumper wire with a fuse in line; it protects the circuit you are testing) and connect the SIG RTN wire to the A.I.R. System Pressure Sensor Signal input wire. With the scan tool hooked up, monitor the A.I.R. System Pressure Sensor volts. It should now read close to zero volts. If a scan tool is not available that has a data stream, then see if code P2432 A.I.R. System Pressure Sensor Circuit Low Input is now set after more than 15 seconds. If either of these have occurred, then the wiring and PCM are good. The most likely problem is the sensor itself.
If all tests have passed so far, and you continue to get a P0411 code, this would most likely indicate a failed A.I.R. System Pressure Sensor, although a failed PCM could not be ruled out until the sensor had been replaced. If unsure, seek assistance from a trained automotive diagnostician. And remember, PCMs must be programmed, or calibrated to the vehicle in order to be installed correctly.
Codes Related to P0411
P2430, P2431 & P2432 Secondary air injection (AIR) system pressure sensor faults – P2430 may set along with P0411 as it is a generic failure of the Secondary AIR Pressure Sensor. P2431 and P2432 are unlikely to set along with the P0411, as their requirements to set are entirely different.
P0418 Secondary air injection (AIR) system Pump Control Circuit – PCM detects a failure of the pump control circuit.
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