93 5.7 cat delete o2 sensor light

[evilunclegrimace]

No, The O2 sensor is concerned with what is happening with the engine, It does not care what happens in the downsteam exhaust.

 

[Schurkey]

I did find the slightest leak on top of the flange weld- a tough spot to squeeze a weld into with it on the truck. It's maybe a half inch in length where the flange is nearly tangent with the pipe. Very small. Nearly impossible to get a weld on without a flexible tip on a gun which I don't have.

www.amazon.com/gp/product/B000BOAZM8/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

No, The O2 sensor is concerned with what is happening with the engine, It does not care what happens in the downsteam exhaust.

...unless exhaust reversion is pulling fresh air backwards into the area of the O2 sensor.

That will depend on the size of the leak, and the distance to the O2 sensor. The smaller the leak, and the further away from the sensor, the less-likely that it's a problem.

 

[fancyTBI]

Fair enough. Like I said, I haven't done it. Truth is when my cat rattled itself to death on my '94 5.7 it never set a code. That was a heated-O2 truck. Come to think of it my '92 5.7 cat came apart as well, and the non-heated O2 didn't set one either.

Richard

Mine rotted off and never set a code even with the open Y pipe. Also heated and a 4.3 truck!

 

[ol-Betsy]

Put a scanner on it, not a code reader, and look at O2 Voltage (~0-.95V) feedback. Below .45V means it's running lean, >.45 means it's running rich. Then look at "Cross Counts", meaning how many times it "Crosses" back and forth over .45V. Yes, OBDI can do all this stuff.

If you have a 1 wire sensor, it may not be getting hot enough to work, due to less back flow restriction. A heated 3 wire will work better.

No shops around have a scanner that will give live readings. I bought an aldl cable, as well as a usb adapter, download tuner pro and am completely lost with finding a bin and xdf. I have no clue what I'm doing at this point so any help is appreciated

 

[PlayingWithTBI]

download tuner pro and am completely lost with finding a bin and xdf. I have no clue what I'm doing at this point so any help is appreciated

I hope you downloaded TunerPro RT. The regular TunerPro won't data log. The .xdf file is to read your .bin, the .adx is for monitoring.data logging.

What service number ECM do you have? It s/b on the top of the ECM/PCM behind the glove box. Then we can look for the correct files. If you look at the box there too, it should have your four letter .bin If (big IF) yours is completely stock you'll have the correct .bin for your truck but, you won't be able to "burn" a modified .bin without a chip eraser and burner. A better way is to upgrade your ECM/PCM to an EEPROM instead of your OE EPROM so, it's easier to "Flash" a chip instead of "Burn" one.

You're looking to troubleshoot, not modify your system (at least not yet) so, get the corresponding .adx file and go to town!

 

[ol-Betsy]

I hope you downloaded TunerPro RT. The regular TunerPro won't data log. The .xdf file is to read your .bin, the .adx is for monitoring.data logging.

What service number ECM do you have? It s/b on the top of the ECM/PCM behind the glove box. Then we can look for the correct files. If you look at the box there too, it should have your four letter .bin If (big IF) yours is completely stock you'll have the correct .bin for your truck but, you won't be able to "burn" a modified .bin without a chip eraser and burner. A better way is to upgrade your ECM/PCM to an EEPROM instead of your OE EPROM so, it's easier to "Flash" a chip instead of "Burn" one.

You're looking to troubleshoot, not modify your system (at least not yet) so, get the corresponding .adx file and go to town!

The ecm has a few numbers on it. Serv. No. 16197427 BJLF
86BJLFK640976299
16198125 BJLF
86BJLFK640976299

 

[PlayingWithTBI]

OK, you have a '7427 PCM with the BJLF .bin

You wanna use the $OD definition files like the "Advanced $OD v200.xdf" and the "A217 $OD TP5 v250.sdx". Here's a link to a bunch of info about the 7427 but, you may need to join the forum to gain access to them.

www.gearhead-efi.com/Fuel-Injection/showthread.php?303-16197427-PCM-Information-0D

It's interesting that you do have a 7427 and BJLF in a 93 - they show for a 94+

 

[Stowburb]

I have a 1993 k1500 and the cat has fallen apart and no longer existed within the exhaust. It has some rust and leaks so I had a straight pipe put in place. I put a new O2 sensor in (OEM ac Delco) and the ecm isn't having it. Still throwing a light. It runs good but I'm afraid it's in limp or running rich. This truck only has 1 factory O2 sensor, and it was pre-cat. My understanding is it's used for fuel trim then so she can't be running right.

I'm looking to not spend the money and replace the cat. What are my options to not only get rid of the service engine light but to more importantly correct the fuel trim, leaving the exhaust at its current state?

Did you upgrade the O2 sensor to a heated sensor? If not then I would recommend upgrading it as the original sensor is a single wire sensor and relies on the exhaust “restriction to heat it up to operating temperature and with a free flowing exhaust system the sensor will not get hot enough to trigger the ECM into “closed loop” it will remain in “open loop” which means it will run only on “pre programmed” fuel management perimeters. This will cause fault codes and poor drivability and fuel efficiency issues.

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Stowburb​

Newbie​

Greetings Nick88,

In order to gain some insight when diagnosing why your computer is throwing a code I find it helpful to read the
GM Service Manual writeup as to what criteria has to be met before the test is run while you are driving.

We can then infer why a solid failure may seem to be intermittent, as well as what else has to working properly
in a supporting role, or end up becoming the straw that broke the diag's back.

Given the above, let's check out the first page of the Code 32 write up in the '89 FSM:

View attachment 369939
(Excerpt from FSM sourced from here: '88+ GMT400 Factory Service Manuals)

So the way I read it, in order to meet all the criteria for this self-diagnostic to run, we have to drive
the truck above 50mph, maintain a steady throttle with a MAP reading of 41-50 kPa. So depending upon how
you use your GMT400, you may run a few errands over a couple of days and never quite string these 3 variables
together long enough for the test to run?

In other words, you getting on the parkway must have finally given the opportunity for this test to run/fail.

As for how the computer infers that the EGR valve is operating, during the test it shuts off the EGR and then
looks for a change in the 'fuel integrator counts'. (That's OBD1 speak, in the land of OBD2 we refer to this as
fuel trims. Note: One of the supposed benefits of the OBD2 rules is that all the manufacturers had to standardize
on industry-wide defined terms instead of each mfg'r using unique terminology in their training/FSMs.)

In English, as a troubleshooter you now realize that the coders are relying upon a functional O2 sensor to be sensitive
enough to detect/feedback these changes back to the computer. IF this was my vehicle, and the O2 sensor has
been installed for an unknown length of time, I'd seriously consider changing it as normal maintenance, and if a
fresh O2 sensor helps this test to pass, all the better.

Now of course if your O2 sensor is fully functional and yet the EGR valve can't deliver the inert gas it's supposed to,
then of course the test will fail. You mentioned that the original EGR valve failed a vacuum test, but the new one
passed. Of course the acid test would be to get the truck up to temp, idling, and then using a hand vacuum pump
(Like this) open the EGR valve and verify that you can directly affect the idle. (runs roughly)

IF applying vacuum directly to the EGR valve does not affect the idle, then you need to restore the gas path that
@PlayingWithTBI was describing in reply #4. If applying vacuum directly does affect the idle, then the next check
is to reconnect the EGR valve to the EGR solenoid, and then see if the solenoid is also working as advertised.

****

Hopefully the above will provide you some troubleshooting food for thought. If the EGR valve opening = actual exhaust
gas allowed into the intake, and the O2 sensor isn't too lazy/asleep at the switch to notice the difference and feeding that
back to your new computer, followed by the EGR solenoid being able to stop the EGR operation, then you have the best
chance of getting this to work despite lowering the exhaust back pressure to one side of the EGR valve.

****

And if I do all of the above and I can't get this test to pass? In the interest of science I would concoct some sort of
temporary backpressure hack and see if I can figure out just how many inches of exhaust backpressure it takes to
make the light stay out...and then share that info here for the benefit of the other TBI drivers. :0)

Hope this gives you a few troubleshooting ideas. (See 1st attachment for the factory checks.)

Let us know what you discover.

Best of luck --
Click to expand...

Great information and advice.

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