VW 2.5 Secondary Air Injection Incorrect Flow (P0411)
The secondary air injection system’s job on your VW 2.5 engine is to prevent excessive emissions. A bad component in this system is almost sure to set off a check engine light. Generally the fault code would be something like “P0411 – Secondary Air Injection Incorrect Flow”. The important thing to note is that when you have this fault code it points you in the direction of the secondary air system, but you will still need to track down which component is causing your issue.
What does the Secondary Air Injection System Do?
The Secondary air system’s basic function is to use an air pump (for VW generally electric) to force additional air into the exhaust on cold start. Pumping the air into the exhaust has 2 main functions, both of which are emissions related. 1 Pumping additional oxygen into the exhaust helps break down hydrocarbons (essentially unburned fuel), this is required as vehicles run richer on cold starts. 2 Pumping that air into the exhaust will heat the catalytic converter up quicker allowing it to reach its efficiency range quicker.
Sounds Fancy but Why Do I care?
If you have an issue with your secondary air system your VW 2.5L engine will set a check engine light. Check engine lights in pretty much all parts of the US means you will not be able to pass inspection. So you need to address this issue to pass. You also need to fix this to prevent further damage to parts in this system. Take a look below for a little more on that.
What parts do I need to replace?
This system is pretty simple on the VW 2.5 engine, it consists of an Electric Secondary Air Pump, Electric Combination Valve, and the hoses and pipes that connect them. You will need to track down which of these is your issue. There are generally only a few ways these fail
- The Combination (N112) Valve Stops Working (may be stuck open or shut)
- The Secondary Air Pump Stops Working
- There is a leak in one of the hoses bleeding off the air the pump is making
- The Secondary Air Pressure Sensor (failed sensor not reading)
- Bad Mass Air Flow Sensor (Less Common)
- Bad Oxygen Sensor (Less Common)
Its important to note that if your combination valve get stuck open you will need to repair this as soon as possible. A stuck combination valve will force condensation from the exhaust into the secondary air pump. This will generally cause the pump to fill with water and eventually will destroy the pump as well.
Secondary Air Injection Pipes
If you have a 2006-2008 VW 2.5 Engine up to production date 6/30/08 you would need to swap to a replacement kit that includes a new updated pipe, pressure sensor and connector adapter.
2.5L Secondary Air Pipe Kit with Sensor and Adapter 07K198125
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