I can tell you EXACTLY what the problem is. I just fixed my original sending unit and am making a video for Youtube. No more having to buy the entire sending unit fuel pump gizmo.
BTW, the dealer now sells a fuel guage replacement part. you dont have to get the whole unit anymore.
I dont want to diver the thread too much from the EGR solution so just PM me or email me and I'll give you the lowdown.

Back to EGR. I am sorting through the re-learning procedure again and checking the wiring further as Kyle has suggested. I cross whatever bridge I come to after those checks.

Gary

 

Ok, I call my problem FIXED. I performed driveability tests for about two weeks after my last post. I thought that since replacing the EGR valve I could not get get it to reset correctly with the computer. I tried every different combination or unplugging the battery cable, reset CEL, and unplugging the EGR harness that I could think of or read about on the net.
Nothing fixed it. The CEL would activate about 15mins on around town driving and within 5 minutes after interstate driving. I also experienced a hesitation at 1100 rpm and slight surging. I was also throwing a CEL for EVAP slight system leak. cant remember the code at the moment.
All this started after replacing the fuel pump/guage combo unit in the tank. I bought the aftermarket unit and had to splice the wires for their new plug.
Well that unit didnt go all the way to full so I had them send me a new unit. Free shipping and I didnt have to send the old one back for credit before they shipped.

The replacement unit was an exact wiring harness fit for the stock wiring on the truck so I had to switch it back. I went to the junkyard and grabbed a plug end from another blazer so i would have plenty of wire to work with.
I also removed the tank from the blazer completely this time. I was worried about the slow EVAP leak CEL code and I read to ensure a good seal on the pump O ring. Forums suggested vaseoline on the seal. I wante dto get a good look at that seal.

So I did that, replaced the fuel pump/guage unit. NOT A PROBLEM SINCE. Went through at least 2 full tanks of gas. No hesitation, no surging, no CEL. OBD2 readouts perfect for shrt/lng term fuel trim.

My conclusion. If you buy a aftermarket fuel pump/guage combo, DO NOT buy or accept the one that has to splice the wires. I dont know how I got the second one that was harness correct. But that fixed my EGR issue.
Kyle may comment on the connection between the EGR and the fuel combo but I dont have the background or testing equipment to answer the theory. I am just an educated parts re placer much like most of us internet repair people.

So, excluding my time spent, I am out the cost of a 130.00 EGR valve due to the wrong pump. Not really bad when you consider the dealer would have molested me. IMHO, sometimes you got to spend a little money to EXCLUDE a part. Like I did with the EGR valve. I was fairly confident it was something else after cleaning mine perfectly, trying a junkyard unit and then a brand new unit. High chances that it WASNT the issue.

Hope this helps some future forum searcher. Kyle, thanks for the diagrams.

Gary B.

 

Hi guys,
I'm having the same problem, aftermarket fuel pump with butt connected harness and p1404 code. I have another consideration. This is a friend's Blazer, and after I replaced the fuel pump, I noticed the truck wasn't coming up to temperature and the heater wasn't hot. So I replaced the thermostat (stuck open) and fixed that. Drove the Blazer a couple miles and thats when the p1404 code first came up. My original thought was that until the engine came up to temperature (which it was not), then the ECM would not be attempting to enable the EGR system (thus no EGR code). So once I fixed the warm up problem, the EGR problem surfaced. That was until I read this post. This is my question: I'm thinking of disconnecting the fuel level wires at the pump temporarily to see if the p1404 comes back. Does this sound like good logic? Thanks in advance

 

I swapped the two black wires on the aftermarket pump harness and it works great. Joe

 

Well there ya go. Glad it worked out for you in the end and was an easy fix! Thanks for posting the follow up!

 

Hi I too just replaced the fuel pump and now i have a 1404 code EGR how do I fix this I know its not the EGR

 

As I said in my previous post, swap the two black wires at the fuel pump. Right now your pump is being incorrectly grounded by the ECM, so correct it before it burns up your ECM! This will fix the problem.

 

hey guys i was having the same code pop up after i replaced my fuel pump so i switched the black wires and now my battery is running down overnight...do you guys think this is a direct problem from switching the two wires...your response is appreciated.

 

I kind of doubt it. One black wire is the fuel pump ground and the other is the signal return for the fuel level, neither of which should have power with the switch off. Possibly the ecm could have been damaged from the crossing (mine wasn't) or you may have pinched a wire by the tank? Check for a current draw with the ecm unplugged and that will tell you if the problem is there.

 

i think you guys need to buy the exact replacment pump, they last longer and you dont have to worry about what wire goes where.. just my 2 cents