MajeSStic_

Hello all, I'm having a little problem with my camaro. Since I bought it the SES light has always been on. I also only get around 18-20 mpg on the highway with casual driving. Previous owner got an after market exhaust installed but never got the o2 sensor reinstalled/welded in. Could this be a problem? Car running too rich? It's funny because I took my old 83 z28 5 speed on the same trip and got almost 30 mpg with its old worn out 305.

MajeSStic_

Or could it just be because of the 10" wide tires in the back?

Uziguy18

iTrader: (1)

what year

a4 or m6?

o2's is part of it

MajeSStic_

1999 SS

M6

Car only has 72,500 miles on it.

eaglegoat

Yes, most likely this is the problem.
What codes?

mrvedit

When you say "but never got the o2 sensor reinstalled/welded in" are you referring to the front or rear O2 sensors?
The front are critical, the rears do nothing other than fault when the cats are worn out.

MajeSStic_

We crawled up under it and found two plugged in on the passenger side. One up high and one a little farther down. Are there supposed to be two more on the drivers side?

1slowbusa

iTrader: (8)

There are 4 sensors, 2 on each side. The two closer to the engine are the ones you need. The ones closest to the rear of the car do nothing but check the cats. To run closed loop, you need at least the O2 sensors that are closer to the engine. If you have cats and want to monitor them, put the other 2 in.

Look under the engine for the front O2 sensor connection. The ones, I believe they are under or beside the transmission are the ones for the cats. If the harness for the front will not reach, you will need to get extensions.

So basically, you need one on each side and they should connect to the connectors coming out from under the engine.

Post a picture if you can.

MajeSStic_

Thats what I thought. But I didnt see any on the drivers side. Ill crawl back under it and try and get some pictures today in between rain drops.

mrvedit

Excellent explanation by 1slowbusa.
There should be and absolutely need to be an O2 sensors on each side of the engine.

MajeSStic_

I'll try and get some pics when it stops pouring with rain.

redtan

iTrader: (5)

Why don't you go and find out what the code is (most places do it for free). Unless you're good at diagnosing things by looking at them (which you might be here with the o2s) that's usually the easiest way to start looking for the problem.

MajeSStic_

I plugged my tuner in to see if it would give me a code and it never did. We set everything back to stock and the light went off. I had a pen out to right down the code but didn't need it lol. I will probably take it somewhere when I go get a couple clutch parts and get them to see if there's a code.

MajeSStic_

Upper o2 sensor





Lower o2 sensor
I was able to locate both upper and lower sensors on the drivers side and both appear to be plugged in. Now I'm at a loss.