1998 SL 500 - P0410 Sec Air Inj Code
 

I have a 1998 SL500 with 93K miles with a check engine light (code P0410) that keeps coming on. It comes on after driving about 3-4 miles, sitting at a stoplight. The idle stumbles for a second and the light comes on when the secondary air pump kicks in. The dealer replaced the secondary air pump and 1 oxygen sensor about 15K miles ago. I replaced the other oxygen sensors, all the vacuum lines, spark plugs and the secondary air system seems to be working properly (the pump runs at various times). I have cleaned the valves that connect to the vacuum lines and manually operated them with a hand pump or 12VDC. I bought a new code reader and here is the data frozen when the fault last occured:

P0410 Secondary Air System

Rpm: 575
Load value 23.1%
MAP Sensor 59 KPA
Coolant Temp 172 degrees F
Short term fuel trim 1 6.2%
Long 1 4.6%
Short 2 39.8%
Long 2 4.6%
Short 3 -100.6%
Long 3 -100.6%
Short 4 -100.6%
Long 4 -100.6%

It looks like it is running out of fuel on one cylinder bank?

Any suggestions?

Most MB scanners can perform an activation of that system & show info on the reaction of the front O2 sensors. Possibly a blockage....