Truth about code 32

[Portedfrankenstien]

The Yukon throws code 32 anytime I maintain speed at, or above 55mph. Now, I understand how EGR works, I've been a technician for many years. However, I've never heard of relating exhaust back pressure being needed for an EGR to operate properly. Now, I know these EGRs are negative pressure EGRs, so I guess it makes sense in a way. My girlfriends brother owns a 95 k1500, so he has the same drivetrain as the Yukon. His EGR operates properly. I have cleaned mine out, and put a new gasket on it, to no avail. So I swapped EGR solenoids with his truck. No fix. So I then swapped EGR valves, and cleaned the one off if his truck out before installing it on the Yukon. Still, code 32. After doing some research, I have found a link where people are saying that if your exhaust is too free flowing, that the EGR cannot operate proper, due to lack of back pressure. I am running 3" exhaust, from y-pipe back. Running a 14" round body magnaflow, and obviously no cat. So, my question is this, is it true that my EGR isn't functioning how it should, due to being a negative pressure EGR, and lacking the back pressure?

 

[Portedfrankenstien]

And also, if this is true, is there any way that I can get my EGR to work properly, without putting a converter back in? I personally feel that an EGR valve is a great thing, and I won't be one of those who just puts a block off plate on.

 

[Ruger_556]

I only do heavy trucks so I don't have much experience with the EGR systems on these engines but the exhaust would have to be in a vacuum to keep the EGR from working wouldn't it? I think there is something else going on. If back pressure was related you could clamp a step down adapter on the exhaust and go for a drive, that would tell you pretty quickly.

 

[Portedfrankenstien]

I only do heavy trucks so I don't have much experience with the EGR systems on these engines but the exhaust would have to be in a vacuum to keep the EGR from working wouldn't it? I think there is something else going on. If back pressure was related you could clamp a step down adapter on the exhaust and go for a drive, that would tell you pretty quickly.

That's not a bad idea. I'll see if I can figure out a way to try it. There are three types of EGRs. A negative pressure, a positive pressure, and an ECM controlled type. Being as these trucks run only a two wire connector to the solenoid, and are marked with an "N" at the end of the part number, this tells me that they are negative pressure valves. And the two wire connector indicates they are not ECM controlled. So in my mind, having a well free flowing exhaust, with very little back pressure, I suppose this could cause an EGR error code, considering they are negative pressure. It doesn't show a single symptom of an EGR failure. It runs perfect, and is very smooth. Never sputters, never overheats, and passes the smog test better than most TBIs that actually have a cat, that I run the smog tests on.

 

[Portedfrankenstien]

I've also tested the connector at the solenoid with my power probe. It is getting power at the ignition power wire, and the ground wire is also good. The valve itself is holding vacuum pressure well at 15psi.

 

[Portedfrankenstien]

Anybody got any input?

 

[someotherguy]

The OEM valves vary greatly in their application and the TBI control system seems very picky about them. Yours may be bad, and the one off your brother's truck may not be the right one for yours. Before driving yourself nuts, I'd try the correct ACDelco or Delphi valve for your application. Skip the parts house brands 100%.

I ran my '94 C2500LD with a gutted cat and a Flowmaster 40 dumped, no EGR issues at all with that setup, except for when the valve went bad - code 32. Replaced with a Delphi EG10099, done.

By the way, the reason the code pops up on you when it does, is the PCM waits for certain conditions to be set before testing the EGR. This involves closed loop, steady cruise state, with throttle and speed only varying a tiny % over a set amount of time. That's when it feels it can safely energize the solenoid and expect a change in the O2 reading to determine whether the valve is working, without interference from too many other parameter changes from stop/go driving, hills, etc. You may already know this.

Richard

 

[skylark]

The first rule of code 32 is: You do not talk about code 32.
The second rule of code 32 is: You do not talk about code 32.

 

[Portedfrankenstien]

The OEM valves vary greatly in their application and the TBI control system seems very picky about them. Yours may be bad, and the one off your brother's truck may not be the right one for yours. Before driving yourself nuts, I'd try the correct ACDelco or Delphi valve for your application. Skip the parts house brands 100%.

I ran my '94 C2500LD with a gutted cat and a Flowmaster 40 dumped, no EGR issues at all with that setup, except for when the valve went bad - code 32. Replaced with a Delphi EG10099, done.

By the way, the reason the code pops up on you when it does, is the PCM waits for certain conditions to be set before testing the EGR. This involves closed loop, steady cruise state, with throttle and speed only varying a tiny % over a set amount of time. That's when it feels it can safely energize the solenoid and expect a change in the O2 reading to determine whether the valve is working, without interference from too many other parameter changes from stop/go driving, hills, etc. You may already know this.

Richard

I agree completely. Here is my issue though, the part number on his truck matched the part number from my truck. EGR from my truck works properly on his (which still has a converter), but didn't on mine. And his doesn't work on mine either. And being as the solenoid is a two wire connector, it's only keyed power, and ground. So the solenoid for the EGR never actually communicates with the ECM. So my thoughts are this, the map sensor communicates with the ECM, and the oxygen sensor communicates with the ECM. one of them isn't seeing what it wants to out if the EGR valve. So... Maybe the MAP sensor, or the oxygen sensor is actually my problem? Or maybe iys a real deal, that being as its a negative pressure EGR, it needs a little back pressure. I can't even begin to imagine how a positive pressure EGR would act, without back pressure. I worked for a muffler shop for a few years, and we had to research a bunch of studies on all kinds of different mufflers. Believe it or not, a flow master creates a little more back pressure than a straight through magnaflow. I'm not saying I disagree with you, so please don't take me wrong. But maybe that slight bit of extra back pressure was just enough to make the EGR operate the way it should. But who knows, because obd1 is not a very smart system, and I'm starting to lean toward the possibility of maybe a bad MAP, or oxygen sensor.

 

[Portedfrankenstien]

The first rule of code 32 is: You do not talk about code 32.
The second rule of code 32 is: You do not talk about code 32.

god d%&# code 32! It seems to be a very big issue with these trucks.