5 different codes for recent Check Engine Light [/align]
[hr]


P0136-Bank 1 Sensor 2
P0300
P0410
P0141 Bank 1, Sensor 2
P0302 Cyl Misfire.


Car runs fine, new spark plugs around 22k miles ago.

I imagine that at least the Oxygen sensor is bad, since two codes were thrown for the same one....could it trigger the misfires?

'01 SLK320[/align]

 

Hi,
1. First step. Cancel codes and see what comes back.
2. Check wiring connector to Bank 1 Rear O2 sensor. NC / Water ingress / Corrosion? Code is CIRCUIT problems although this does include circuit resistance which could be a bad sensor.
3. Need to look at the waveform / voltage coming from "faulty" O2 sensor vs other bank to determine if different. If so I agree sensor is likely culprit.

Something doesn't quite stack up since fueling is controlled by the upstream O2 sensor rather than rear sensor. So I don't understand the misfire. Have you looked at the plugs? Were they OE spec or some fancy aftermarket part when changed? Plug colour look OK? (Careful not to overtighten when you replace). Replace plugs in different cyl. Does misfire move to P030X?

P0410 code is secondary air injection (electric air pump at front of engine). This injects air to light up the cats when they are cold and is triggered by the rear O2 sensor. If the upstream cat (fuel system control) fails to control emmissions leaving cat 1. Air injectiop is on all M112 R170 SLK V6 since the California tune engine is fitted to all markets worldwide )complexity reduction).

Looks pretty conclusive that O2 sensor is bad but I like to be sure before swapping out parts.

If you do change I suggest you use OE part (especially if you only change one) although others (cheaper) will work. Some give all sorts of issues especially Universal types due to wiring implications.

Stuart

 

As Stuart said, clear codes. Its worth cleaning maf too.

Bazzle

 

I used the Correct Bosch plugs, and they have been in for 22k miles with no issues. MAF was replaced around 10k miles ago.

I'll see what happens when I scan again.

 

OK. Just do as I stated including inspecting and moving around the plugs.
So many things can cause a misfire. Coil pack, leads, wiring ....+ as Bazzle says the MAF.
Need some additional info so reset and scan.