So I rebuilt my 4.3 earlier this year. I also removed the catalytic converter when I had the flow masters put on it. Never got a C.E.L. until 4000 miles later. No damage to O2 wiring, new sensor, and new TPS. Comes on above 60mph @ 2000+RPM. any ideas? This is on an 89 4.3 TBI. I know the ECM is not bad, because I chipped a spare ECM with an Edelbrock chip and added Venom injectors a while back. Code has shown up with both ECMs and is only above 60mph. I'm stumped.

 

check for exhoust leaks, also you say you had it chipped and injectors, that would alter stock fuel trim and therefore you may need a diffrent o2 sensor or it could be a bad sensor. are you able to check ecu parameters with a scan tool on that engine? if so check to see whats going on at 60 mph and report. pretty sure it has to do with all that extra fuel your dumping into the engine. alot of time the mas may need to be replaced too when rechipped thats if that uses one

Trouble Code 13 indicates that the exhaust stream oxygen content sensor (O2 sensor) is not responding as expected. When cold, the sensor is 'biased' by the ECM to about 450 millivolts. Before it warms to at least 600 deg F (315 deg C) it acts as an open circuit and when the ECM reads it, it reads the 450 mV bias. The ECM expects the sensor to warm in a short period of time and begin sending its own voltages.

The conditions for setting this code are:

engine running at least 40 seconds and
no code 21 or 22 (TPS errors) present, and
coolant temperature is at least 118 deg F (48 deg C), and
O2 sensor voltage not fluctuating (i.e. steady between 350 and 557 mV), and
TPS signal indicates above idle (over 6%), and
all the above conditions met for more than 8 seconds

Typical causes for this code include:

1) Defective or degraded O2 sensor
2) Deposit contaminated O2 sensor (running leaded fuel, RTV silicone deposits etc.)
3) Corroded/defective O2 sensor connection
4) Defective sensor ground circuit
5) Defective connection at ECM
6) Defective ECM

do you have a thermostat installed?

 

Thanks for being the 1st to respond to my thread. The o2 sensor (Bosch) is new, although it is very well possible it could be defective... Will be eyeballing things for the next few days as I did some work to it this morn. I'm ruling the defective ECM out because I have had two ECMs in it, and same code on both. I do have a 190 degree thermostat installed. Honestly, I think a bad EGR valve was the cause of the code. I was getting a bad EGR code for sometime before code 13 and then the egr code stopped and 13 took it's place. It has been dumping more fuel because of the valve being bad, and o2 getting the tail end of the problem. I installed a new EGR on it this morn. So far, so good. Will know this afternoon when I hit the highway to get my truck aligned. Everything I read on a faulty EGR points to the CEL coming on at cruising speeds, and false o2 codes... I hope the new EGR has solved this, if not, I will pursue the steps you've outlined to narrow down the possibilities. Thanks again! BTW, even before the chip and Venom injectors, the code was being thrown.

 

Well, I thought the new EGR solved the problem, but it did not. I guess next week I will remove the o2 sensor and replace it. It's still under warranty, so, we'll kill that possibility.

 

How would I find the pin location on the ECM?

 

How to look up Service Engine Soon codes without scan tool - S-10 Forum


copy and paste on your browser its a how to

 

LMAO! I knew this! I was talking about the connection pin for the o2 on the ECM. So if it is faulty, I can bypass it.

EDIT: http://www.chevythunder.com/fuel%20i...ts.htm#1986-89 pinouts (ecm #1227165)

 

Found out that I have a exhaust leak somewhere. This may be giving me my troubles. Will update soon.

 

If the leak/or muffler is right there past the 02,it'll go nuts. I ran open exhaust right past the cat for a few days after i got this blazer (rusty exhaust falling off) and the 02 sensor was going nuts until i added some pipe back on it later.

 

Thanks. I had my cat gutted and some exhaust work done to the 02 sensor, where that entire section was replaced. I will go over that thoroughly.