Wideband through EGR on 04 Silv.

[NyteSnyper]

I've been reading alot on this subject recently as far as people hooking up their widebands through either the EGR or the AC Pressure lines and logging them without having to get "upgrades". I have been debating doing this however, I don't want to mess with the AC pressure deally (gets hot here in TX) and my truck doesn't have EGR.

My question is, even though my truck did not come with EGR, would I still be able to hook my wideband up to a "pin" on the PCM that would have supported EGR on similar models (say an 02 Silv. PCM has pin 55 as EGR Sensor, yet mine says not used, yet almost all other pins on the pinout sheet are identical between the two) and still have it work in the same way? Any info on this would be appreciated!

[EC_Tune]

Look at the 8.1L ECM wiring diagram for your same model year. AFAIK 8.1L's use EGR.

[NyteSnyper]

Look at the 8.1L ECM wiring diagram for your same model year. AFAIK 8.1L's use EGR.

Okay, so the 8.1 has the same PCM? I was talking with one of the techs at work (I work at a chevy dealership) and he told me that they were NOT the same.

[EC_Tune]

If the 8.1 has an allison maybe not. If it has a manual it should be the same PCM. They use same/nearly the same O/S in them as the 1/2 ton & 3/4 ton trucks.

Check the replacement service #'s for both. From my experience with the 1/2 & 3/4 ton trucks, gas motors, the PCM's from 04/05/06 (*maybe* 07, old body style) were interchangeable.

[NyteSnyper]

Thank you for your assistance thus far! I have compared the pinouts for an `04 8.1l with my `04 4.8l and have found that all pins are basically the same, except the 8.1l has pin 55 as EGR position signal (and the supporting pins in other slots). Would I be able to hook my 5v output from my wideband to this pin and be able to see it? or would i have to do an 8.1 OS/some other kind of trick?

[EC_Tune]

No tricks necessary. Just add it to Pin 55 and then monitor the EGR Position in the table view. Check some other threads around here for the calibration routine.

BTW: Which connector? Blue? Red? Green?

[NyteSnyper]

PCM C1, Blue Connector - Pin 55.

My 2004 Silv. 4.8 says - Not Used
2004 Silv. 3500 8.1 says - EGR Valve Position Signal

[EC_Tune]

Sounds like you're good to go. I would try something like a AAA battery with a 2K ohm resistor in series from Pin 55 Blu to the sensor return line(may want to ID the sensor return line for the EGR as well) to see if things are operating correctly before proceeding.
Then it's just a matter of taking the EGR Pintel Position (voltage or %) and transforming it into CalcAFR to use for tuning.

Can you verify that Pin 55 Blue is used from 03-07 on 8.1's? And the signal return pin?

That will help out a lot of truck guys if they can get that info as well.

EC

[NyteSnyper]

Well, from the availability of pinouts i have, it appears to me, that in 05 they changed things, as pin 55 on the 05 pinout is "Not Used" on the 05 8.1l. I also looked further back, and apparently, 03-04 is the only years pin 55 applies.

As for the return line, I'm kinda confused on this. (I thought I knew a little about wiring and what-not, but apparently you have blown me out of the water... ) I have on the PCM C2 Connector (Red) a pin 7 "EGR Voltage Supply" and a pin 41 "EGR Solenoid Control". I figured it would be as simple as wiring the output of the wideband to the EGR Position signal and logging that with a custom PID for the conversions and what-not. Now I'll go back to .

[EC_Tune]

Hmmm. I just tuned an 06 8.1 and it has EGR. Wierd...

On the wiring. Can you post up a pic of the EGR system wiring in total? Usually they have a pin designated Ground or Sensor Return and usually it's black or black with a white stripe.

[NyteSnyper]

Well, it wouldnt let me pull the pictures out, and I dont have access to a scanner, so printing and scanning was out, but i'll do this...

04 8.1 EGR - 5 pin connector - Black

Pin A - White Wire - EGR Solenoid Control
Pin B - Purple Wire - Low Reference
Pin C - Brown Wire - EGR Valve Position Signal
Pin D - Gray Wire - 5-Volt Reference
Pin E - Red Wire - EGR Valve Supply Voltage

Now looking at this, I can tell if I ever had EGR, I would be prolly tapping into the brown wire going to the PCM, however, I'd be guessing that the purple wire is my return? but then I'm unsure, cuz the whole Grey wire thing has me second guessing myself... in either case, Low Reference goes to C1 Blue Conn. Pin 41; 5-volt reference goes to C1 Blue Conn. Pin 47. I might also mention that there are four 5-volt references in a row along pins 45-48.

Edit: Might I also mention that on the pinout for my truck, pins 45-48 are also 5-volt references, yet pin 45 is for the (A/C), 46 is for the (EVAP), 47 is ("Not Used"), and 48 is blank. I'm guessing these are the grounds?

Edit 2: After looking around at some other schematics (mainly the MAP Sensor schematic) I'm more than positive now, that the "Low Reference" is the ground. I have my 2-bar MAP sensor sitting right in front of me, and it has what pin does what, on the little sticker on the sensor. Matching what the schematic says to what the sensor says on it, 5-volt reference = 5volt input, signal = just that, the signal, and low reference = ground.

[EC_Tune]

5-volt reference is a 5-volt output from the PCM. There's a 5-volt regulator in the PCM that supplys voltage to each sensor that requires it. Pins 45-48 will all have 5 volts on them when the PCM powers up.

"Return" in GM-speak is always "sensor ground". Sensor ground is not necessarily (or generally) chassis ground. Wierd that they chose purple for a "return" wire. Not unheard of but different...
Gray on a sensor connection is usually a 5 volt output on most all GM vehicles.
Red is usually a battery voltage wire. Pink/black stripe is usually a Key On battery voltage wire.

C1 Blue Conn. Pin 41 = Wideband ground goes here
C1 Blue Conn. Pin 55 = Wideband output wire goes here

[NyteSnyper]

ok, so now, what if im also connecting a gauge to monitor A/F when i dont have the laptop handy... would grounding the sensor to the block be fine without sending the ground to the PCM, or would i have to ground at the PCM with both? or ground sensor at PCM and gauge at block? (I have the innovate LC1, using output 1 for gauge, output 2 for PCM)

[EC_Tune]

There's a wiring diagram in the EIO section for the LC1. The only thing that changes is the connection to the PCM will be replacing the connection to the EIO. And the PCM connection will be permanent.