pin 8, code 13 states: "O2S (Lambda) control system operating at rich or lean limit"

which would seem to me to indicate a bad O2 sensor, but not code is showing up on the #2 pin, so I'm not sure if this is correct. Any ideas?

Also, I've been trying to find the exact location on where the oxygen sensor is on my car, and I know it's under the front passenger side of the car, but where exactly, and how do I gain access to it? Thanks

John

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1995 E320 119,000 miles

No, that code doesn't mean that the O2 sensor is defective!

It means that computer imputs have caused the computer to go to a maximin adjustment factor! All the way RICH or LEAN.

Vacuum leaks, fuel pressure, OR defective air mass sessor are the most common problems

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I agree .. First look are the easy ones .. see if there is gas in the vac line at the pressure regulator ..common
..then look EVERYWHERE for vac leaks,
..also even a plugged/dirty A/F can bring this code up

Thanks, M.B. DOC & Arthur


A coupe more questions:

Where is the pressure regulator located?

What's the easiest way to check for vacuum leaks? I've seen several ways to do it in previous threads, so I just wanted to know the quickest/least involved way.

Thanks
John

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1995 E320 119,000 miles

PR is the can at the front of the fuel rail .. over by the termo housing .. it has a vac hose hooked to it .
There should be no gas evidence in the hose or you have a ruptured reg diaphragm .. allowing both too high a FP and raw gas getting sucked into the engine .. so you can see how this would easily upset the A/F mixture .
vac leaks are just searched for , check every hose ,, suspect on that chassis are around the throttle/intake area and under the engine front plastic cover ,, the white plastic line going to the SOVs is infamous and many Techs just can that line and go with a full length rubber one [ the plastic ones crack and break from heat fatigue]

My 94 E320 had the same code, after checking/replacing all the other items on the list, replacing the Engine Control Module finaly fixed the problem. My car did not have any drivability issues, but I did not like the illuminated check engine light!!

Takes about 5 mins to replace the ECM. Dealership wanted $2200 but I got one from the salvage yard for around $150. It was from a 95 E320. I did not have to program it, as the car it came from had the same California Emissions, Traction Control etc.

If you take your car to the dealer, they will probably look at the live adaptation values as they swap out components like the O2 sensor, MAS, ECM etc. with known good ones to find the root cause.

Electronics on these cars are unreliable, OVP, Fuel Pump realy, Compressor Control Relay, Aux Fans and/or relays, AC Push Button units are a few items that have an above average failures rates on this model.

The Fuses may appear good visually but maynot be working. Also, the wiring harness disintegrates, creating short circuits, which maybe the root cause for the above average electrical issues.

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Zafar
94 E320 58000 Miles