Hey I posted here a few months ago about a blazer I got, some mice chewed through the PCM harness. I'll have to go back and refer to my diagram (haven't looked at it in a while), but when rewiring the PCM I had one leftover wire coming out of the harness that was SUPPOSED to go to the EGR. I want to say it was brown. The problem I had is, there is no pin in that slot on the PCM connector and no severed brown wire anywhere to tie into. What's up with that?

Do I really need it?
my mpg is only 17mpg at the moment which seems low to me... But it's my first 4.3 and blazer. so is the the fact that the egr is physically still hooked up and potentially allowing unmetered hot exhaust back in affecting my MPG?

 

Ok here was my OP back in May, it has the diagram I am referring to. The 2001blazer.pdf. If I remember right I have a brown EGR wire and no pin in 55. It's not just missing, it's capped off like all the other slots that don't have wires.
https://blazerforum.com/forum/engine-transmission-35/2000-s10-blazer-4-3-nv3500-pcm-printout-101605/

 

What year is yours? Never mind - its in your original post.

 

2001 blazer, it's got the zr2 package and a 5 speed

 

Here you go. 5 wires to PCM for the EGR. See attachment

 

Disappointing, I checked the fuel economy.gov site and it says it averages 14 combined mpg. Lol. I guess I should take my 16-17 and shush. What about you guys? What do you get?

Still curious about that EGR wire though. I also had a few left over wires that are for auto transmission I think as well.

 

Here's the 2000 Schematic for comparison. All EGR go to different pins on the PCM. So wiring harness for 2000 is not wired right for 2001 PCM. Maybe you can switch the wires for the EGR, but what else can be wrong? Better get a 2001 Wiring harness IMHO.

In my experience, you will never get above 17-18 mpg with a 4WD Blazer unless you are driving slower than 55. 14 combined is what I happen to get. Blazers get poor fuel mileage. My 2004 Z71 Avalanche has a V8, 4WD, and weighs 6500#. It will beat my 2001 4x4 Blazer by a couple of MPG in any situation, around town or highway. Once I put the blazer on a trailer and pulled it 300 miles with the Avalanche. Total would be about 13,000#. Still 13 average on the highway (65 mph w/AC on). Never really understood the poor mileage with the Blazers - they do have fuel injection and a PCM. I guess the V6 is basically a 1955 technology engine, while the Avalanche has a much more modern and apparently efficient 5.3 LS engine.

 

I don't have a cut brown wire, or a pin, only a plug in slot 55. That's my issue lol. I'm wondering if it was tied into another wire somewhere, not necessarily on pin 55. Like a voltage wire or something.

 

To clarify, I was mistaken about the year in my OP I linked. i hadn't picked up the truck yet or the title. So it is a 2001 and I followed the 2001 diagram.

I'll snap a pic later. Break is almost up. But most, if not all of the red pcm connector was eaten by mice. I backprobed everything with multimeter, every sensor and wire, and found continuity between sensor and the split at the pcm. Everything works and is accounted for except for that weird brown EGR wire.

 

In Post #7 of your original thread that you linked to you said you used a 2000 wiring harness in your 2001. Well, year 2000 does not use pin 55 for the EGR (hence the plug), and the rest of the EGR wiring is wrong as well. You need the 2001 wiring harness.

Compare the two schematics - 2000 vs 2001. All the wires go to different pins on the PCM.

What split are you talking about - there is no split I can identify. Brown wire goes to Connector C1 pin 55 to tell the PCM what position the EGR valve is in. I think you will find a brown wire in connector C2 pin 10 of the 2000 harness - but it's not so simple as switching that one wire (all of them are wrong).

2001 Blazer used the 12200411 PCM (this is the 411 PCM the tuners talk about swapping in). 2000 did not. Different PCMs. Not the same PCM and not the same wiring!