Hello,
I have a 2000 Blazer that's give me a headache. Here's the deal:

For a 2000 Chevy Blazer 2x

I have to get it smog checked, however, it's going to fail because the 'Service Engine Light' is constantly on. I ran a scan and got the P1133 (O2 Sensor) and P1404 (EGR Valve) code errors.

So I replaced the three O2 Sensors (that I could find) and I just installed a brand new EGR Valve today. After doing so, I ran the truck for a while. After a few miles the 'Service Engine Light' went out, to my freaking surprise! However, about an hour later, bam, it pops back on.

So I get home and run the scan again; and again I get a P1133 code and two P1404 code errors (the second being the pending/maturing code). It's pretty frustrating and I'm now at a loose. I don't know, maybe tomorrow when I fire it up it will go out, I doubt it.

If anyone has any suggestions as to what a good next step might be it would be greatly appreciated.

Thanks for your time.

 

Found this online might help you out.
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Possible reason (very likely) for the false P1404 code is that the plastic piston of the EGR valve position instrument (LVDT?) wears over time and starts reading a different position at valve closed than what it was when the EGR valve was first installed.

When the car was built and the computer circuits energized for the first time the computer learned the EGR valve closed position signal from the valve position instrument that is built on top of the valve itself. Over time, when the instrument wears, a slightly different signal is sent to the computer and when it differs enough from the 'Valve Closed Signal', that the computer had learned, the trouble code P1404 is set and the 'Service Engine Soon' light comes on.

Replacing the EGR valve with a new one does not necessarily fix this problem because the 'Valve Closed Signal' between valves is slightly different and it is just pure luck if your new valve would give a 'Valve Closed Signal' close enough to your original valve's signal not to set the trouble code. This is why the new EGR valve 'Valve Closed Signal' must be re-learned by the computer.

So, what this all means is that if the P1404 is a false code meaning that the valve pintle is not stuck open, then new 'Valve Closed Signal' can be re-learned by the computer using the old valve.

For fixing this problem the tool you need to have is a simple OBD II code scanner that can be used to erase trouble codes. There are many scanners of different price range on the market. I purchased one from AutoZone for about $90.

A code scanner is a very handy tool to have and I recommend everybody who is just slightly hands on type of a person to get one. It will end up saving a lot of money over time.

The fix goes like this:

1. Disconnect the wire harness from the EGR valve.

2. Turn key ON and erase the trouble code(s) from the car's computer AND TURN KEY OFF IMMEDIATELY WHEN THE SCANNER SAYS CODES HAVE BEEN ERASED. DO NOT TURN KEY ON BEFORE YOU RE-CONNECT EGR WIRE HARNESS.

3. Re-connect EGR wire harness and your problem should be fixed.

I learned this fix from OBDII.COM where carfixer and kozloski discussed it and I think kozloski was the one who provided the solution, so thanks to them.

There was also other people stating that this fix really works. Now I have joined this group of people as I got mine fixed using this trick also.

I believe erasing codes with wire harness disconnected and turning the key OFF right after P1404 code has been erased re-sets the 'Valve Close Position' reading in the computer and triggers computer to re-learn position next time the key is turned ON.

If you don't have an OBD II scanner and don't want to buy one some car part stores may erase the code for free, but if you have it done there you must tell them about turning the key OFF at the right moment. Other wise the re-learn process does not take place.

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Alot of the time all you need to do it clean all the crap out of the old EGR and reuse it. EGR valve is about $200 you can save by giving the old one a good cleaning

As for your P1133 code, you may want to run a real good look for a cracked manifold on that side. I like to get them nice and hot and use something like a pen laser to look for exhaust leaks. You can see the beam really easy if there is a small exhaust leak.

 

Thanks so much for sending that along. I think that will help, hopefully! Thanks again.