I found two codes on my '94 C280: P0400 EGR Flow Malfunction and P0411 Secondary Air Injection Incorrect Flow. What should I check next?

try this to clear the EGR flow
 

malfunction. You will have to clean out the "pipe" from the egr valve to the intake manifold. This can be as simple as "rodding" out the line from the egr valve to disassembling the connection at the intake end and cleaning it out. Do a search on EGR and you will find this thread.

The other (I would imagine) has to do with your air pump system, maybe the line plugged or the pump inoperable. Wait for someone more knowledgeable in this regard to answer this one.

Jim
'85 300D - no check engine light
'95 E320
'97 CRV

The EGR and Sec AIR switchover valves are both on the front of the head and both use the same vacuum source. I would be sure the vacuum line has good vacuum and that the outputs aren't switched. The two systems work at different times.

Check valve
 

There may be a vacuum check valve in between the AIR and EGR switchover valves. Test it for leaks. Also make sure AIR pump is working when cold.

On my car, the LH-SFI module sends a 'turn-on' signal for each function. Not sure how it's done on your car but probably similar since they're the same year.

Had similar problem but only with AIR. Took all components associated with AIR (switchover valve, check valve, vacuum lines, and EGR switchover valve) apart but could find nothing wrong. After re-assemblying, it worked! No codes since.

[Edited by JimF on 04-16-2001 at 06:40 PM]