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Check Engine Light on 86 Mercedes 300E reveals o2 sensor cutoff

3K views 6 replies 4 participants last post by  Ian P. 
#1 ·
My check engine light is on and the car starts hard needing a little help with the pedal. It appears that the o2 sensor is cut from the computer. If anyone is familiar with this problem please advise on where and how I can check for a loose wire on the engine or under the car. Thanks
 
#3 ·
Check your OVP relay, I had the same problem on my car. Replaced the OVP, problem solved.

-Tubs
 
#5 ·
Not sure if the 86s had wiring harness issues, I know the later M104 engines like mine did. But not sure about the 86 300E, might want to check that wiring for some crispy insulation.

-Tubs
 
#6 ·
Tubs300E - 2/6/2004 12:43 AM

Not sure if the 86s had wiring harness issues, I know the later M104 engines like mine did. But not sure about the 86 300E, might want to check that wiring for some crispy insulation.

-Tubs
Thanks. I took the car to one of those do it yourself carwashes and hosed it down really well under neath. Now the check engine light only comes on when I hit the brake. Pretty weird. It appears there is definitely a loose connectiion somewhere. I'll try to jack up the car and look at the O2 sensor. Stayed tuned.....
 
#7 ·
RE: O2 Sensor

The connection to the O2 sensor is under the passenger floor mat and floor panel.
Try disconnecting it to see if it changes anything.
These are pretty easy to change and cheap if you get a "universal" sensor. The only difference is it doesn't have the MB plug mounted, you have to splice the wires.

Ian P.
 
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