E36 OBD1 O2 Sensor Failures
 

Hello,

I have a 1994 325is e36 with OBD1. In the past 40 thousand miles the o2 sensor has been replaced about 10 times. Always turning on the CEL light. Relay checked. MAS checked. Plugs replaced. Not sure what is happening. Put a Desno O2 sensor in at one point and it went 10 thousand miles. When that one went out this summer I put another one in. now 6 months later CEL is on and O2 is again out.

Car is 5 speed manual. Yes there are different part #'s for O2 sensors for manual and automatic depending on the manufacturer.

What causes these to burn out. I replaced the ECU at one point. Car only has about 95 thousand miles. This started at the normal O2 interval at 60 thousand miles and has been a problem ever since.

Do I have a bad CAT? Can I put one of those spark plug non foulers in the CAT to move the O2 sensor out a little farther so it does not get so hot?

Anyone have any ideas. Has anyone had this happen to their OBD1 E36 and what was or is the cure.

Thank you!
__________________
Rick

Rick,

Why don't you check out our Pelican Technical Article about O2 sensors here: Pelican Technical Article: About Oxygen Sensors.

There's a lot of content in that thread that may help answer your issues. If you do not find something in there I am sure one of our technicians may help better assist you with your particular issue.

RE:E36 OBD1 O2 Sensor Failures
 

Hello,

Those are not the answers to the specific questions that I am asking. I have replaced the DME box and and installed my chip specific to my car. No changes at all. Car burns out o2 sensor every 5 to 10 thousand miles. Often o2 relay replaced too.

Usually goes out in dead cold of winter. Heater in the o2 sensor is burning out. Right now CEL is on. New o2 sensor, relay and new plugs. CEL was reset now back on after 5 minutes. Car is running but I the answer why this is happening. Anyone else had this same specific problem on E36 325is? This is OBD1 car from 1994.

Thank you,

There is no such a problem with the O2 sensors, the sensors in my E36 M3 are now in 50 k miles and still work properly.
Have you ever tried to check with a good fault diagnosis tool to see if there are any faults? Best is a real good BMW tool which goes deep into the system.
How to the O2 sensors look? One can diagnose a lot from the colour.
Sometimes, oxygen sensors can become contaminated by elements from within the engine. Exhaust from an overly rich fuel mixture can foul an O2 sensor, as will leaded fuel. Antifreeze or silicone residue resulting from faulty gaskets can have the same effect.

Hi Triodeotl - I looked at the link that Luccia posted and it seems that at the bottom of the article there are a bunch of comments from some folks who have had the exact same issue as you (or close anyways, O2 sensor burns out every 5 to 10 thousand miles?). Anyways if you scroll down to the comments in the discussion thread from that article, someone might have posted an answer already or might get some inspiration from those ideas. Good luck!

OBD1 has only one sensor in the front that is heated. Not sure what M3 you have but likely has four o2 sensors. My 1st sensor went 60 thousand miles but since then nothing but 1 or 2 a year since up to 94,000 miles.

Its a problem have big Snap On Tool. Works on OBD1 where other aftermarket tools do not.

CEL is on.

Codes are:201 & 13

201 = Control

13 = o2 Circuit

Sensor tip is black carbon. Car would hardly run once warmed up because the heater in the o2 sensor was burned out because the relay could no longer cycle it when the DME told it to turn he heater for o2 on.

Spark plugs look clean not carbon no bad coils.

Codes

201

13

E36 OBD1 O2 Sensor Failures
 

o2 sensor voltage is under half volt at idle and .47 when accelerated. Wiring harness appears to be fine.