2004 E320 drive cycle & secondary air monitor not ready - PeachParts Mercedes-Benz Forum

97 SL320 · #1 08-01-2018, 08:29 PM

OBD 2 constantly runs monitors under all conditions. The non AC might be for the fast track all monitor test.

The secondary air test on my 97 runs after the engine is warmed up and returns to idle. It runs the air pump then looks for the O2 sensor to read lean ( low voltage for a traditional unit , for a wide band it just looks for a lean condition ) Also, in normal operation the air pump only runs in the first minute after a cold start.

I'd expect the 04 it use the same strategy, listen for the pump to run.

ROLLGUY · #2 08-01-2018, 10:19 PM

Quote:

Originally Posted by 97 SL320

OBD 2 constantly runs monitors under all conditions. The non AC might be for the fast track all monitor test.

The secondary air test on my 97 runs after the engine is warmed up and returns to idle. It runs the air pump then looks for the O2 sensor to read lean ( low voltage for a traditional unit , for a wide band it just looks for a lean condition ) Also, in normal operation the air pump only runs in the first minute after a cold start.

I'd expect the 04 it use the same strategy, listen for the pump to

run.

Quote:

is the air pump working? replaced alot of them over the years..... if it needs a pump, get a new relay-dealer only-they are updated. good luck, chuck.

I checked the pump by powering it up, and yes it is working. I also started the engine cold, and the pump did not come on. I don't have a CEL, so I assume the fuse and wiring are good. Could the relay be bad and not turn the CEL on? Do you know where I can find the relay? I have a parts car (well actually a running usable one), so I can borrow parts for testing.

tjts1 · #3 08-02-2018, 02:14 AM

Try this

ROLLGUY · #4 08-02-2018, 10:30 AM

Quote:

Originally Posted by tjts1

Try this

Been there, done that, thanks. Just this morning I started the car, and the air pump did not go on. I started the sedan, and the pump immediately came on. I pulled relays out one at a time until the motor went off. I plugged it back in to make sure I had the correct one. I took the relay from the sedan, and replaced the one in the wagon. Still no go. I put the relay from the wagon in the sedan, and it seems to work. This all tells me that the relay is fine, but something else is keeping the secondary air pump from activating.