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  #1  
Old 09-01-2010, 03:33 PM
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Default P1404 - Replaced EGR...

I guess this is as good as any to ask. I replaced my fuel pump gas guage deal in the tank and since then on that same day I have had a P1404 code. I can clear it with my Digimoto software and it comes back in about 15-20 mins.
I cleaned my EGR just like the thread says. Cleared, 20mins later, same P1404.
I tried the re-learn method for the computer, unplug, clear code, re-plug. 20 mins later, P1404.
Went to salvage yard. Got another EGR vlave for 15, 20 mins later, P1404. Ran 2 tanks fuel through and still every 20mins, P1404.
Took plunge today and bought Autozone EGR with 2 year warranty for 119. 20 mins later, P1404.

I am dying here. I dont believe any of the EGR valves are bad. That would would be 3 separate valves. Of course anythings possible, but I doubt it in this case.
Yes, I could go back and try another Autozone valve as they will give me probably as many as I want. But how many should I exchange before we all say, nope, its not the valve.
The harness looks good as far as I can see. Used some contact cleaner on the plug connection, looks fine.
Let me repeat, this started immediately after I changed the fue lpump sending unit. 20 mins later.

My digimoto shows good looking sht/lng term readings. O2 sensors look good on voltage.
After replacing the fuel pump unit I also have a slight hesitation at 1100rpm. Changed fuel filter 2 times since pump change. Once was clogged. 100k miles. Original I assumed.
Fuel pressure 62psi and increases as throttle is juked. Never seen it go below 59. I only changed it as the gauge stopped working.

Car ran perfect before changing fuel pump. No hesitation, no codes ever since I've owned it.

Is there ANYTHING else that can contribute to this issue? Cause evrything I've read says this code is directly related to pintle position and computer interpretation of that location

2000 S-10 Blazer, 4.3, 4wd. Owned about 1 year. Replaced cat converter and pipe after fuel pump install due to rattling, spark plugs, the usual suspension parts.

Thanks,
Gary B.
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Last edited by Kimchoc; 09-01-2010 at 03:45 PM.
  #2  
Old 09-01-2010, 04:45 PM
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*Moved to a new thread in 2nd Gen Tech* - The tech article submission/discussion section is for the submission of new articles and the discussion of the article content, not for technical troubleshooting help.

I am not sure if you saw the obd2 listing for this code:
P1404 - EGR Valve Circuit Performance Actual Position Greater Than Commanded

Have you tried to go through the trouble shooting chart?
  #3  
Old 09-01-2010, 07:56 PM
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Thanks for relocating me.

I read that write-up and understand EGR valve operation and how the computer arrives at setting a P1404 code.
And I read the steps to re-learn the new EGR valve. I performed those re-learn procedures probably 6 times. I have also disconnected the battery for well over and hour.
I dont have a scan tool to set EGR values. I cleaned it twice. Substituted a used one from salvage I just replaced it with a new one. Yes I realize any part, even new could be bad, and i could go swap one at Autozone I merely ask, just when enough is enough. Surely I couldn't get 3 or 4 bad ones right off the shelf. I mean, you have to figure that ONE of them would work. If thats the suggestion then I can go swap one. But my hunch tells me something else is amiss.

Haven't I just skipped to the end of the diagnostic chart and eliminated the EGR valve by replacing it? I could now go back and check the voltage. I know this procedure is a little not what you are used too, but in reading all about the P1404 on the net I often found a replacement of the EGR valve cured it (once in awhile cleaning cured it) and I never found that the voltage was incorrect on any thread that I read. So I went with what everyone else said to fix it.

Here is a basic summary of how I re-learn the EGR valve:

"It appears that the secret to getting the EGR valve to relearn the closed position is to reset the trouble codes with the valve disconnected and immediately turn the key off so it doesn't have time to set the "EGR Circuit" code. Then connect the valve and turn the key back on and PRESTO!"

Could I be performing that operation incorrectly? Could you provide a quick link to a scan tool that performs EGR valve testing? Is it affordable to the home repair person?

EDIT: I've just looked at the schematic. It appears that there is some connection between the fuel pump sending unit and the EGR valve at the S102 connection. Is that correct? Also some connection to the fuel tank pressure sensor? I have noticed that when I was changing the fuel filters in the AM on a cool engine, I first hooked my fuel test gauge to the rail to bleed pressure and there was none to bleed. Could there be some relation to the EGR valve?

Thanks,
Gary
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Last edited by Kimchoc; 09-01-2010 at 08:24 PM.
  #4  
Old 09-01-2010, 08:07 PM
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I doubt you will like the price of any of the bi-directional scan tools that are available, but that is the next step to getting this problem solved. In a few rare cases, the PCM itself has been the culprit. I haven't looked, but I thought my AutoEnginuity w/ GM Enhancements was fairly economical at $500.

Have you ohm'd out the wiring between the EGR and the PCM while moving the harnesses around? Could possible have a bad wire that is causing the code to set.
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Old 09-02-2010, 07:29 AM
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I peeled back loom and looked at the wires for about 6-7 inches from the plug. They looked fine, no chafing. I mean, they are protected by the loom and the plug itself looks fine.
No I haven't ohm'ed them. I've been studying the schematic and trying to determine which wire has which type signal or volts. That is something I could do.

I just have this hunch that something in the replacement of the fuel sending unit is an issue to qualify.

Can you tell me that this P1404 code is ONLY related to the pintle position? Is there any way that anything else could trip this code? because if not, then I really am left to believe that the EGR valve itself is the issue.
I just cant believe the co-incidence of several different EGR valves (3) going bad at the SAME time as I replaced the fuel pump.
The code was issued within 15mins of the replacement and test drive and has been constant since the replacement. Its not like the code was issued a day later of I ever had the code before.
The replacement pump was an aftermarket that required changing a plug on the wiring harness at the tank. I just havnt been comfortable with that whole deal. The color codes didnt match up and I had to call their tech support line for instructions. Just not comfortable with that.

Thanks,
Gary B.
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  #6  
Old 09-02-2010, 08:00 AM
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Quote:
This sensor uses a variable resistor with a 5 volt reference, a signal circuit, and a ground. The signal circuit monitors changes in voltage on the variable resistor as the pintle moves.
If the ground, 5V reference, or sensor return to the PCM are damaged or otherwise compromised, this code could set. Given that the pintle position is sensed via a variable resistor, returning a voltage back to the PCM on the return wire, anything that modifies that voltage will cause an inaccurate pintle position reading.

Wiring can be damaged inside of loom. Someone dropping something on the harness can damage what's inside the loom without visibly damaging the loom itself.
  #7  
Old 09-02-2010, 01:18 PM
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I understand that clearly. I think the odds of it happening are remote.
Its also clearly a drivability issue. I just drove 22 miles before the CEL came on again. All highway driving except 2. The code appears to set when driving at a low speed.
This is a predictable code setting time and driveability period. Not something that is random depending upon a chaffed wire.
I'm not ruling out what you say, just moving a chaffed wire issue to an extremely low probability. And I appreciate your prompting.

I know I haven't dropped anything on the loom. I could barely get the wire out of it as it it so well protected. I've been driving this vehicle for over a year and it has always run perfectly. I change the gas guage/fuel pump and the issue starts.
Most forums will always advise you to look at the last repair that you performed if you start to have problems.

I'll take a closer look at the wiring further down the loom and see if I can get some readings from the wiring.

I'm also going to change back to the original fuelpump/guage and retrace my connections and steps in that process.



Thanks Kyle
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  #8  
Old 09-02-2010, 02:44 PM
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Corrosion, mechanical damage, etc - whatever mode of impact, this test is SO simple and quick that it begs to be performed. The results will give further direction. It is a used vehicle too.
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Old 09-02-2010, 03:20 PM
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Kyle, yes I will do that.
I have been reading again today. Many threads talk about the re-learn issue. So many guys have the same problem. cant get it to stop cel after new valve.
Can you point me to the correct re-learn procedure from GM. I have read several different methods.. this is also an easy fix and can be eliminated..

thanks,
Gary
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  #10  
Old 09-02-2010, 04:22 PM
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Interesting that I've had exactly the same problem since a fuel pump replacement. I've cleaned the EGR valve and the code just comes back after about 20 mins driving. The additional problem I get is my fuel gauge just reads empty all the time, other than the occasional time it will read full ! I am 100% sure this is a wiring / grounding problem, it just physically where to look first ?
Old 09-02-2010, 04:22 PM
 
 
 
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1404, 79, blazer, chevrolet, chevy, code, connector, diy, egr, ignition, p1404, relearn, replaced, reset, s102, switch, valve


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