Hi everyone,

A little backstory first - I have a 1984 Firebird that I recently removed the stock 305 and replace it with a 350. I removed all emissions stuff and put headers on it. I did replace and re-install the o2 sensor, though. I kept the stock carb and manifold too. When I drive, the check engine light will come on. It's code 13 which is for the oxygen sensor. The car runs great it's just the check engine light keeps coming on. Any idea what the problem is? Would it hurt the engine in any way to just remove the check engine light?

Thanks,
J

 

Sounds like either 02 sensor is bad or is not connected. possible burn through wire on new exhaust. You can check if sensor is good by using ohm meter. Let me know if you do not know how to perform test.

 

I replaced the O2 sensor with a new one, however I had to splice about 4 foot of wire on to it so it could reach the threaded hole on the header. I'll check the wire though for melting....however, the car runs great now anyways, so if that's not the problem, will it hurt to just pull the Check Engine bulb and leave everything as is? Code 13 is the only code the ECM is showing....

Thanks,
J

 

i f you pull the check engine bulb how will you know if you get future codes?

 

I replaced the O2 sensor with a new one and the Check Engine Light still comes on with code 13....could it be anything else? I did remove all emission stuff when I put my 350 in, but I reinstalled the O2 sensor in the header.

Thanks,
J

 

Had this same problem on my 92 305TBI...

(takes deep breath)...

whats happening is when you first start the car in the morning and its cold, the computer runs the engine in "Open Loop" mode where it does not listen to the sensors until a couple of things happens... Engine warms up to certain temperature and O2 sensor starts to get a reading and a couple other things I'm not certain of... but all these things has to happen or it stays in Open Loop... the computer is getting no signal from the O2 Sensor so it throws Code 13 at this time...

The computer has a designated ground wire that comes out and bolts behind the drivers side head (at least on my 305TBI) along with a couple other wires...

I cut these wires and didnt even think twice whenever I first got the car and replaced the drivers side head gasket (bolt wouldnt come off)... Could not for the life of me figure out what I did wrong until someone sent me a schematic from the official GM book for CODE 13... all I did was cut the wire at the PCM and ran another wire from there to a ground close to the O2 sensor and VIOLA! No more code 13...

At the time, I am not certain of exactly which wire, have to check the schematic when I get to my home computer...

 

Okay sounds good....please post the schematic when you get the chance!

Thanks,
Joe

 

Well, here you are...

 

Just as another little thought here, I had a 1985 Z28 with the 305 engine in it and was getting the code 13 also. After changing two O2 sensors and still having the problem, I borrowed the dealers service manual and found the problem was a mis-adjusted throttle position sensor. Adjusted it and never had the problem again.