TBI, ODB1 code 13, 02 Sensor circuit? Specs included..
 

Using our shop OTC/Genisys scanner, I have a code 13 showing on my 1991 blazer 4.3L TBI 4x4
says code 13 is 02 Sensor Circuit
Im having trouble finding info on what this might mean.
This is a recent motor install, the "new" motor has 60k, has been run about 30 minutes since install.

Here are the specs for the engine at Idle
RPM 700
TP Sensor V .45v
Trottle angle 9%
coolant temp 178
battery 14.4 v
Idle air control 30
air control solenoid On
Air switch On
Block learn Mult 128
Diagnostic state Road
Knock signal No
Loop status Open
MAP voltage 1.18 v
Manifold absolute pres 10iHg
02 Cross counts 0
02 Fuel state Lean
02 Voltage 0.45 v
PROM ID 3151
TCC clutch Unlock

Do these specs look OK? Its been having idleing issues, low RPMs and shaking (was dropping to 580 rpms at times), but it ran good for me tonight, at 700rpm.
So whats the code 13 mean?
Thanks in advance..

RE: TBI, ODB1 code 13, 02 Sensor circuit? Specs included..
 

Oxygen sensor circuit open or no activity

Basically, what it is saying is the O2 sensor is not "switching", going high to low as mixture changes. You can try and reset the computer, (pull the fuse, or, disconnect the battery for a minute...) and see if the code resets. You are getting a voltage reading, at least, you have one in the specs there. With the engine running, does it change at all? or does it stay constant? Is the O2 sensor new? Or is it the orginal that was in there? Did you use any RTV on the "new" motor?

RE: TBI, ODB1 code 13, 02 Sensor circuit? Specs included..
 

Thanks for the reply.
The 02 sensor is old, but I have no idea how old. I did not remove the 02 sensor.
I used very small amounts of RTV on the motor, only for small things like sealing block drain plugs, some on the oil pan gasket, and some accessory bracket bolts (I didn't have loctite).
I ran the engine for about 20 minutes with the diagnostic scanner hooked up.
According to the scanner, the O2 sensor voltage was .45v & .47v at all times, between 700-2000 rpm. Not much of a change.
I reset the ECM/ECU before doing any scans, and this code 13 popped up while the scanner was hooked up, so it is an active code. It was running about 5 minutes when the code appeared.
The "02 Fuel State" was changing from "Lean" to "Rich", back and forth, at around 2000rpm, but then went back to "Lean" at idle. Does this mean the sensor is working?

What kind of voltages should I be getting from the 02 sensor?

RE: TBI, ODB1 code 13, 02 Sensor circuit? Specs included..
 

That is correct, block learn 128, 0 cross counts, open loop = no O2 sensor activity. Is the sensor wiring hooked up?

RE: TBI, ODB1 code 13, 02 Sensor circuit? Specs included..
 

Voltage should cycle rapidly between about .4 volts, and a little less the 1. If it does not, replace the O2 sensor, and the problem should go away.

I have found the using RTV on things like valve cover gaskets, and intakes, kills the O2 sensor. I guess something about the products of it curing plays havoc with O2 sensors, and they stop working..... Can't swear to the connection, but, on motors that I have used RTV, within a week I end up replacing the O2 sensor, not as consistant on motors I do not..... although, I haven't done a motor in a few years......

RE: TBI, ODB1 code 13, 02 Sensor circuit? Specs included..
 

OK, 02 sensor is replaced. Voltage is showing around .47v at idle, and .3v to .6v during regular operation. It goes into "closed" mode operation, which I assume means the system is all working. Idles and runs great!

However, it still wants to die when idleing in drive/reverse. Not sure why. RPMs drop to around 580 at times, idling in Drive. Can a troublesome transmission cause this to happen? EGR valve is clean..

Thanks for all the help so far!!

RE: TBI, ODB1 code 13, 02 Sensor circuit? Specs included..
 

The computer has to relearn the idle, it should figger it out in a few minutes. If not, look for the usual suspects, fuel pressure, vacuum leak, internal fuel leakage, etc.