Howdy,

I received a code 4-3-6 in my A2 socket and I'm wondering if the rear O2 sensor is really the culprit. I reset the code a few days ago and it returned with the same CEL light. Should I just bite the bullet and replace both sensors front and rear or just the rear?

TIA

CJLomax

95 850 GLT N/A

The rear O2 senses the output of the cat converter. I would first check all vacuum lines and elbows, especially those under the battery tray and the one under the thermostat. Then clean the throttle body and see if that helps.

Klaus
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(V♂LV♂s 1995 854T, 1998 V70R)

Thanks Klaus,

The TB and the PVC are clean I check them monthly, however I haven't checked the elbows or the hoses. I'll do that this evening.


CJlomax

Hmmm ... still pulling that 4-3-6 code every other day and no issues with PVC or vaccum hoses. It looks like I'll have to replace the O2 sensors. I'll probably change both since they may have been in there well over 100K miles.

CJLomax

If over 100K miles, probably a good idea. I would change the front one first (most often the one that goes) and go with the rear one later if the code persists.
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1998 S70 T5 Emarald Green Metallic, 2004 V70 2.5T Ruby Red, Previous Owner of Black '94 850 Turbo Wagon. My cars have been running so well lately they've got me worried.