Well, after replacing the the two upstream O2 sensors with AC Delco new, my SES light went off after two drive cycles. It satyed off for about a week for about 100 miles, then came back on yesterday. Again, I have a relatively new EGR valve, recently cleaned when a new screened gasket was replaced. I think we are on summer blend gas now in Minnesota. Guess, I'll have O'Reilly read the code again, but if it comes up P0404 again, then what??

I know my MAF is clean. I hate to bring it to a shop, because I am trying to learn the mechanics of this creature so I can maintain this vehicle myself. There may be some ego involved, of course. But, I'm afraid if I bail and head for a shop, I will be out looking for a Jeep GC I-4 inorder to recover from my PTSD.
So, any more ideas out there? Thanks Blazereenos.

 

Post the DTC's in the order they are retrieved. P0404 is more than likely an electrical circuit problem, rather than a mechanical problem. https://blazerforum.com/forum/diagno...plained-37693/

 

Wow! Lots of good info there. Seems a bit "above my pay grade", but will get the scan and get back to you. I'm sure curious to learn what is behind all this.
Thanks for the response, AGAIN!

 

Ok. got scan at O'Reilly and the two print outs they provided are for a P0404 and P1404. I am not sure what order they came in. However, I have been getting P0404 codes before I replaced the O2 sensors (upstream). The P1404 is new to my experience. The print-out states that both are related to the EGR valve. One for a Closed position, and one for a OPEN position. I have a relatively new EGR valve and it was cleaned about two weeks ago when I replaced the gasket with a new screened one. I know there is a chance it could be bad, even out of the box, but how likely is that?

Presently, I don't know how to test if it is:
1. "Sensor signal circuit is shorted to VREF or system voltage.
2. "EGR sensor signal is shorted to voltage."
3." EGR sensor ground circuit is open or has high resistance".
4. 'EGR sensor ground or to voltage circuit is open."
5. "EGR sensor signal circuit is open, shorted to ground or power."
6. "PCM has failed".

One other thing: Here in Minnesota they are switching gas blends from winter to summer. So, I just filled with a 91 octane, no ethanol blend for recreational and power equipment needs. I figured it probably would not be a "winter blend', as people are using it for their motor cycles, outboards, lawn equipment, etc. Also, I thought a little higher octane may help clean things out a bit. My SES light went off for a day, then came back on. So I am at the same place as before.

Anymore ideas or do I head for the shop?

 

Thought I'd start a new thread, in order to get as much help as possible:

Ok. got scan at O'Reilly and the two print outs they provided are for a P0404 and P1404. I am not sure what order they came in. However, I have been getting P0404 codes before I replaced the O2 sensors (upstream). The P1404 is new to my experience. The print-out states that both are related to the EGR valve. One for a Closed position, and one for a OPEN position. I have a relatively new EGR valve and it was cleaned about two weeks ago when I replaced the gasket with a new screened one. I know there is a chance it could be bad, even out of the box, but how likely is that?

Presently, I don't know how to test if it is:
1. "Sensor signal circuit is shorted to VREF or system voltage.
2. "EGR sensor signal is shorted to voltage."
3." EGR sensor ground circuit is open or has high resistance".
4. 'EGR sensor ground or to voltage circuit is open."
5. "EGR sensor signal circuit is open, shorted to ground or power."
6. "PCM has failed".

One other thing: Here in Minnesota they are switching gas blends from winter to summer. So, I just filled with a 91 octane, no ethanol blend for recreational and power equipment needs. I figured it probably would not be a "winter blend', as people are using it for their motor cycles, outboards, lawn equipment, etc. Also, I thought a little higher octane may help clean things out a bit. My SES light went off for a day, then came back on. So I am at the same place as before.

Anymore ideas or do I head for the shop?

 

You'll need a DVOM to test each of those circuits.
The P1404 and P0404 are both EGR problems.
More than likely the same problem is causing both DTC's to show up.
Higher octane might not improve performance. These things are
programmed to use 87. The PCM will compensate for higher octane
using the knock sensor, but it is limited on how far it can advance the timing.
If it can't advance it far enough to take advantage of the higher
octane, you're throwing your money away.


Using too low octane fuel or inoperative EGR will cause spark knock.
Using higher octane might decrease the spark knock slightly, but
might not affect performance.

 

Always appreciate the Captain's advice.
As an update on my SES light issue, here's what's happened:

After putting some 91 Octane gas in the Blazer my SES light has gone off & on a few times. It now appears to be staying off, but I'm not yet convinced it's fixed yet. Will hope it continues when I refill with 87 octane and run it a bit. My intention and hope was that the 91 octane was a summer blend, as I think some winter blend is still around here in Minn. I realize the higher octane could actually make the engine run cooler in some cases. Anyway, I don't have a DVOM I trust, even if I thought I could do the check properly. But, if my light stays off, I guess the electrical connections might be OK. Got any videos on how to do that stuff??? (good project for the Cptn.).

I did put a couple of gallons of older gas that has hanging around for snowblower, motor cycle and lawnmower use. It had some Stable and Marvel mystery oil it. I figured it would have little affect with a fresh 91 octane fill after.

So, that's the story to date. Wish me luck. Now it's off to electrical school and bracing for what appears to possibly be an oil leak from the timing chain cover. UGG!!
I expect you will be hearing from me soon. Have a great Spring!

 

Please keep us updated on the problem--- esp. if it comes back. We here in the S.E. have problems with 10% Ethanol in the gas. They are threatening to go to 15% Eth. It is giving small engines with carb's fits. They are now coming out with Ethanol additives. But which one is best? After one month , the Ethanol goes bad. Glad we don't have winter/summer blends to contind with.

 

SO, the saga continues:
The SES light went out, as I stated, after a few drive cycles. Then the vehicle sat for 12 days while I was in Florida. Upon my return, after a day of driving short trips, the light came back on. I thought I could detect some surging just prior to this. It remained on for 3 days of casual driving, then the SES light went out again. The Blazer may be running better now, but how can I really know with such a temperamental vehicle? I just filled with fresh gas, which must be a summer blend by now. But, I suspect this GM devil will continue to be a problem, in spite of all I've done to remedy the problem. I am surprised to still see so many on these Blazers on the road - without bullet holes.

 

I'm sorry but I don't see where you have done anything relevant to fix any problems with your tempermental devil! The problem is not due to summer/winter gas blends or oxygen sensors. If you want to fix it yourself, then buy a digital volt-ohm meter (don't you need this for electrical school?) and get to the diagnosis charts. This forum can help with that. You also might want to get your own inexpensive OBD2 scanner, such as the Torque Pro App for Android with wireless bluetooth OBD2 adapter (total cost about $30) as there is much more you can do with it than spit out codes and a list of likely problems (like you are getting from O'Reiley). This forum can help with all of this. But if you're not going to do your part, there is very little we can do to help you.

Didn't you have a great shop that found your air cleaner snorkel problem for you? Why not have them look at it. They sounded quite competent.