ODBII Trouble Codes reset in 1995 W140
 

I borrowed an ODBII scan tool for my 1995 S320 (W140). All the data I've seen shows that the S320 was one of the few models in 1995 to actually be ODBII compliant.

I pulled the following codes:
p0411 Secondary Air Injection System - Incorrect Flow
P0400 Exhaust Gas Recirculation Flow Malfunction
P0300 Random/Multiple Cylinder Misfire Detected
P0302 Cylinder 2 Misfire Detected

None of which seem to be causing drivability issues now.

The problem is that when I try to clear the codes - they don't seem to clear. That is to say, that the codes are still present immediately after the Scanner claims to have successfully cleared the codes. This occurs even if I clear the codes and re-scan a moment later with the engine not running.

Is there an issue clearing codes with the 1995 (early ODBII) S320 model, or am I doing something wrong?

I would just like to actually clear the codes and then see if they re-appear.

Any help appreciated.

It is rare for the Diagnostic module not to clear properly. Something going on with the scan tool. Try disconnecting the battery for a while & see if the codes are cleared.
The codes P0 300 & P0 302 will cause running problems.

I suggest you change the plug resistor boots under each coil
[ all 3] and check archieves for 'EGR tube blockage -104 eng'.

Also check vac line in front of engine under plastic panel for cracks/disconnect to switch-over valves to EGR and AIR pump systems..
These are all common probables to your fault codes on 104 eng models....

Spark plug supperssor
 

Arthur is right once again. I recently changed the 3 coil suppressors (spark plug boots) and my 1995 E320 drives like a new car. My idle was slightly on the rough side until I changed out the suppressors. Cheap fix ($40) with outstanding results.

I am not sure which parts you mean by "3 coil suppressors". What do they look like, and do you have the part numbers?

By the way, I was able to clear the codes using M.B.Doc's suggestion - the scanner seems to be doing the job now.

I'll drive a few days and check for the codes again, but replacing the coil suppressors sound like a decent idea regardless...

<<and do you have the part numbers? >>

Fast Lane has them for $9.94 ea.

Part # F1010-84561