Technical Description of OBD-II Trouble Code
The secondary air injection system on Bank 2 is experiencing insufficient flow.
What does that mean?
This code is a generic powertrain code that applies to all makes and models from 1996 onwards.
However, the specific troubleshooting steps will vary depending on the vehicle.
The secondary air injection system is commonly found in Audi, BMW, Porsche, and VW vehicles, as well as some other vehicles. It consists of an air pump, an exhaust manifold, an input check valve, a vacuum control switch, an electrical input circuit for the vacuum control switch, and numerous vacuum hoses.
This system injects fresh air into the exhaust system during cold starts to provide oxygen and aid in the combustion of harmful emissions, specifically hydrocarbons. After approximately one minute, the system shuts off.
If the air pump and check valve are faulty, they are usually easier to replace. However, many of the vacuum lines are located under or behind the intake manifold, making them difficult to access in most cases. The P0492 code indicates a fault with the system, typically indicating that the secondary air flow is too low on Bank 2. Bank #2 refers to the side of the engine that does not contain cylinder #1. For Bank #1, refer to code P0491.
Other trouble codes related to the secondary air injection system include P0410, P0411, P0412, P0413, P0414, P0415, P0416, P0417, P0418, P0419, P041F, P044F, and P0491.
Symptoms
Symptoms of a P0492 engine code may include:
Potential Causes
Potential causes for a P0492 code may include:
Diagnostic and Repair Procedures
Most of the diagnostic tests must be performed when the engine is completely cold. Some follow-up tests may need to be conducted after the engine has cooled down again, which usually takes a few hours. Some tests may also generate additional fault codes. Remember to clear all fault codes once the problem has been identified and repaired.
1. Check the pump. Ensure that the engine is completely cold. Remove the pressure hose from the pump or from the manifold check valve, whichever is easier to access. Have someone start the engine while you check if the pump is running and pumping air out of the end of the hose or outlet nipple (depending on where it was disconnected). If air is pumping, proceed to step 4. If not, go to step 2.
2. Unplug the electrical harness connector from the pump. Apply 12 volts to the pump using jumper wires. The terminal with the brown wire is ground, and the other terminal is positive. If the pump runs, go to step 3. If not, the pump needs to be replaced.
3. Ensure that the engine is cold. Connect a multimeter and have someone start the engine for this step. Test the pump harness connector to ensure that it has 12 volts by checking the power between the two terminals in the pump harness plug. If you have 12 volts, repeat the first three steps to ensure that no mistakes were made. If you do not have 12 volts, check the fuses and the relay. If you find a faulty fuse or relay, replace it and repeat this step to ensure that there is power at the harness.
4. Ensure that the engine is completely cold. Remove the pressure hose from the check valve. Check if air is coming out of the hose when you start the engine. Do not turn off the engine. After a minute, does the valve close and stop the air flow? If so, the check valve is working properly. If the valve did not open, go to step 5. If the valve stays open, remove the vacuum control hose and start the engine (the engine does not have to be cold for this test). If the valve stays open, the valve is faulty. If it closes, the vacuum control switch is likely the problem.
5. For this step, you will need a vacuum pump, which is available at auto parts stores. Start the engine with the vacuum pump attached and holding a vacuum check valve nipple. If the valve is open, release the vacuum. If the valve closes, the valve is functioning correctly. If the valve does not open at all or does not close, the valve needs to be replaced.
6. Allow the engine to completely cool. Attach the vacuum to the control hose at the check valve. Start the engine. You should have at least 10 to 15 inches of vacuum. If not, you may need to take the vehicle to a shop, as further diagnostic testing requires the removal of some engine components. If no vacuum is present or the vacuum readings are low, proceed to step 7.
7. Locate the vacuum control switch in your vehicle. Trace the vacuum line from the check valve to the switch. Take note of any hardened spots in the hose, cracks, or loose connections. Replace the hose if you find any of these issues, then repeat the test in step 6. If you still have no vacuum, you may need to remove engine parts to access the switch.
8. Remove the input vacuum line from the control switch. Attach a vacuum gauge to the input hose to test manifold vacuum while the engine is running. If you have no vacuum, replace the vacuum line and repeat this step.
9. Apply vacuum to the input nipple of the vacuum control switch. The valve should close, and the pump should not hold a vacuum. Apply 12 volts to the two terminals of the control switch using jumper wires. If the switch does not open and release the vacuum from the pump, then the switch needs to be replaced.
Secondary Air Injection Video
We are not affiliated with the producer of this video, but we are including it here as an additional resource for diagnosing your air injection problem(s).
