I was driving home today in my 1985 Camaro 305H LG4 and the check engine light came on. I have not seen the check engine light in this car in about 150K miles. It came on 2 times about 5 minutes after start up and stayed on less than a minute each time. I got home and checked the codes and I have 12 and 13. I read that 12 is a check code. So I have code 13. The definition is O2 sensor-signal stays low ("lean") during warm engine cruise or sensor circuit is open or left sensor circuit is open (dual sensor models). I am sure I only have 1 on this old of a car. What exactly is this saying? Do I just need a new O2 sensor or do I have problems further up? I don't ever remember replacing the O2 sensor on this car. It may be the original one with 251K miles on it. I am sure it wouldn't hurt to change it but I am wondering if I am running lean. Thanks, Robbie

 

its a wonder yours didn't go out on you about 100K miles ago. I replaced mine, thinking it was the reason my SES light was on. Came to find out later it was another problem. But as hot as these cars run, those sensors don't last too long. Hope that helps

Will

 

9 times out of 10 when you get any kind of 02 code it is the sensor itself. In rare cases the wire can get burnt or cut, but it's usually the sensor.

Besides, if you haven't replaced it in as long as you say, it would be a good idea to do it anyway. You should see a gas mileage improvement at least.

Yes, you only have one sensor. It's located near the collector on the driver's side exhaust manifold. Buy some more WD-40 and let that thing soak a good while before attempting to remove. Also, make sure to get a Bosch unit, don't let them try to sell you a cheap foreign knockoff (been there ). I replaced mine a couple months ago when I changed my headers, only cost $34

 

Thanks. I will get a new O2 this weekend. I haven't seen the light come on again.

 

$34 sounds too expensive.
I paid less than $18 for my bosch unit from Advance Auto parts.
I think it might have been even cheaper, like $13.

 

Mine ran me around 30 bucks also. Sure that wasn't a knock sensor??? For 15 bucks I mean.

 

It was an O2 sensor. the ones for my LT4 are $35 each and those are the 3 or 4 wire type which cost more. I do remember using only one $20 bill to buy the O2, I remember this since I am also low on cash and am very frugal with spending money.

 

Remember that these cars have MILES of vacuum lines. If you get some significant vacuum leaks going you'll throw a Lean O2 code. Had the EXACT same problem with my brother's 85 LG-4. Turns out the vacuum reservoir for the HVAC controls (little plastic "mailbox" above the brake booster) had gotten a nasty crack in it and leaking massive vacuum. After fixing the O2 code went away and the idle speed also dropped quite a bit- right back to the factory specified idle speed- imagine that!

 

If possible, get rid of all the smop crap and ECM controlled stuff and put a nice carb and intake on it. I got a lot of power going to a carb on my LG4. 133K miles on my car and I ran a 14.94 @ 91.67mph with only a carb, intake and open element air cleaner, still ran the stock exhaust and manifolds.
Here is a pic of my engine bay all nice and neat