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Username Post: P0420/P0430 codes        (Topic#266393)
PeteyG708 
Forum Newbie
Posts: 43

Age: 26
Loc: El Paso, TX
Reg: 03-23-11
07-19-11 05:50 PM - Post#2115892    

Hi all,

Returning poster...new truck though.

I have a 98 Silverado 1500 Z71 with the 5.7L V8. I went to get it inspected and it failed...because the CEL light wouldnt turn on at start. So I pulled apart the dash, replaced the bulb inside as well as some others, and it went back together with no problems. Of course, the light was on. I got the battery disconnected and reset it, and it came back.

Autozone read the codes P0420 and P0430 - "Catalyst Efficency Low - Bank 1" and "Catalyst Efficency Low - Bank 2". So I dont know where to start really, as they tell me it could be the oxygen sensors and other people tell me it could be the cats. While the cats arent too bad to replace ($80 universal fit for OBDII at Autozone/Orileys), It still is pretty expensive taking it to a shop.

What would you all recommend? Should I pull the Oxy Sensors first then reset the computer, or should I go ahead and tear it all out and do the cats too?

Registration from GA is coming up, and I gotta put TX plates on it, and TX needs the forms for inspections.

Thanks in advance!
Pete
------
- 1998 Chevrolet Silverado K1500 Z71 Ext. Cab (Vortec 5700 V8/4L60E 4 Speed Automatic/Push Button 4WD)
- 2002 Ford Taurus SES (Vulcan 3.0L V6/AX4N 4 Speed Automatic)


 
someotherguy 
Moderator
Posts: 25575
someotherguy
Age: 44
Loc: Texas
Reg: 08-01-03
07-19-11 06:19 PM - Post#2115912    
    In response to PeteyG708

Welcome back Pete,

Those would be the post-cat O2 sensors; you can replace them (kind of pricey) or attempt to trick them out by using spark plug non-fouler tips - some have had success with this method.

After you clear codes on an OBD-II system like your truck, you have to drive it for a while before it's "ready" to be tested again. In other words if they see a recent code clear on it, they won't inspect it.

Richard
94 C2500LD / 94 C1500 / 06 300C SRT8
Check out my truck shop projects


 
PeteyG708 
Forum Newbie
Posts: 43

Age: 26
Loc: El Paso, TX
Reg: 03-23-11
07-19-11 06:49 PM - Post#2115926    
    In response to someotherguy

Richard,

Thanks for the response. I dont know how good the fowler will work, seeing as this truck failed twice; once when the guy came to TX from GA, and once when I took it to get inspected (before I found out the light was out). so it has to pass this time.

I found the Oxy Sensors (Post-Cat) at Autozone for about $50 a pop, which is better than I expected. The truck has 189,000 miles so I would assume those cats are still good, especially for a 98.
Pete
------
- 1998 Chevrolet Silverado K1500 Z71 Ext. Cab (Vortec 5700 V8/4L60E 4 Speed Automatic/Push Button 4WD)
- 2002 Ford Taurus SES (Vulcan 3.0L V6/AX4N 4 Speed Automatic)


 
64belaire 
Contributor
Posts: 202
64belaire
Age: 38
Loc: Gun Barrel City,Tx
Reg: 10-04-09
07-19-11 06:57 PM - Post#2115929    
    In response to PeteyG708

http://www.p0420.com/
http://www.obd-codes.com/p0430

hope this helps.

 
355Cheyenne 
Senior Member
Posts: 3765
355Cheyenne
Loc: Northern MN
Reg: 10-27-04
07-19-11 08:23 PM - Post#2115988    
    In response to 64belaire

I am fairly versed in this subject. There really are three possibilities:
1-exhaust leak(extra o2 in exhaust triggering mil, going to be after the upstream o2 sensors)
2-Bad catalysts
3-bad o2 sensors

The cats are going to be the most expensive fix but how do you know which is the problem? This is hard then you have both banks at a fault. If 1 bank faulted then you could at least swap the sensor. The upstream sensors are different so that doesn't work.

If you want to fix this right, the best I can come up with as the cheapest is to start by purchasing 1 sensor. If you install the 1 and it doesn't clear the corresponding code then it wasnt a bad sensor and I would try on the other side.
Now if it ends up being the sensors, then get another. if it ends up not being a sensor then at this point you are out $50.

The next thing I would do is follow along the exhaust while running but exhaust/motor cold (so to not burn hands) and feel for a leak. If none found easily then likely your last option are bad cats.

The method Richard explained with the spark plug non foulers works EVERY time for me. But I don't have to worry about emissions testing. You do so this could be risky. If they do a proper inspection they will find these and you will be in deep dodo (potentially) if they run an exhaust probe you will fail anyway and I am not sure if that would raise a flag. I used to have to deal with testing in WI and they would put a hose over the exhaust on older cars but 96 newer they just plugged into them. Now I guess I am leaving that up to you. If you want to take that chance I can give you the instructions on how to make a spark plug non fouler adapter but I am not responsible for your choices and I will only recommend them for off road use to avoid any liabilities... (BTW it is a $5 fix.)
98 Silverado k1500 4x4 350


 
PeteyG708 
Forum Newbie
Posts: 43

Age: 26
Loc: El Paso, TX
Reg: 03-23-11
07-20-11 02:24 PM - Post#2116211    
    In response to 355Cheyenne

Yep, Emissions are very picky. I think since this is a 98, they plug into the computer. I honestly dont know if they run a scanner over the exhaust or if they put the probe in the tailpipe. Never seen them do that to my Aveo.

In any case, I am gonna do the inspection on the exhaust and cats (holes/leaks and such), but I am most likely gonna replace the downstream O2 Sensors. The truck is 98 and has 189K, so chances are they have never been touched. Found some Densos at Autozone for $50 a pop so it will only cost me $100 to do both. It triggered both codes so why not just do both?

From what I have read (Thanks for the links 64BelAire), bad connections (corrosion on connectors, loose connectors, etc) at the location of the O2 sensor could trigger the CEL. Figure I will get that checked out.
Pete
------
- 1998 Chevrolet Silverado K1500 Z71 Ext. Cab (Vortec 5700 V8/4L60E 4 Speed Automatic/Push Button 4WD)
- 2002 Ford Taurus SES (Vulcan 3.0L V6/AX4N 4 Speed Automatic)


 
64belaire 
Contributor
Posts: 202
64belaire
Age: 38
Loc: Gun Barrel City,Tx
Reg: 10-04-09
07-20-11 06:20 PM - Post#2116294    
    In response to PeteyG708

Talk to some of your loacl shops also. Theres a way to test them with a volt meter.

http://youtu.be/XQ9vtD_ssjg

 
archie1407 
Forum Newbie
Posts: 24

Loc: Wyoming
Reg: 10-26-09
07-20-11 08:40 PM - Post#2116318    
    In response to 64belaire

I've got a 98 Tahoe 4dr 4x4 and replaced all the o2 sensors. Still been getting P0420. The Chevy diagnosis says to inspect wiring and sensors and if nothing is found, replace the cat(s). However, thinking I could save some $$$, I ordered magnaflow universal cats and was going to have a local guy put them in. There is a flange on one and that makes it very difficult to weld in a universal cat. A poor weld and you could have Co2 poisioning...not an expert here, just sharing what I was told. You may need the cats and y pipes. Magnaflow, bosal and walker all appear to carry the OEM cats. Local guys tried to stick it to me by telling me the part numbers that I would need...only it was for the California emissions parts...which I don't need in Wyoming. Good luck

 
davenmer 
Forum Newbie
Posts: 14

Age: 36
Loc: Jacksonville, FL
Reg: 02-16-10
07-21-11 10:03 AM - Post#2116443    
    In response to 355Cheyenne

Can you tell me how to do the non fouler trick? I would like to try seeing I have the same codes. I live in Florida so no inspections here Thanks!!
David

1996 Chevy Z-71
5.7 Vortec 173,000 miles


 
355Cheyenne 
Senior Member
Posts: 3765
355Cheyenne
Loc: Northern MN
Reg: 10-27-04
07-21-11 11:47 AM - Post#2116465    
    In response to davenmer

Go to any parts store, most will have a HELP! spinning display. In there they sell a spark plug non fouler. (that it what it is labeled as) and it looks like a tube with one end threaded on the inside and one on the ouside. I used to be able to get them long enough to just buy them and use them but I haven't been able to find them long enough anymore, but that is o.k. they come with two. What I do is cut the outside threads off 1 and place it ontop of the other where it has inner threads and then weld it on to each other. This gives me a long tube. pull the down stream o2 sensor out and screw the non fouler in, then screw the o2 sensor into the non fouler.

If I did not make the extension or if I screwed the 2 together the o2 sensor will bottom out in the non fouler before it threads in all the way.

Then I clear the code and see if I get any more codes. If I get the same code or a bad p2 sensor code then I drill the non fouler hole larger and usually that is it.

Every time I have done this it has worked. Trucks with weak catalysts or even no cat.
98 Silverado k1500 4x4 350


 
davenmer 
Forum Newbie
Posts: 14

Age: 36
Loc: Jacksonville, FL
Reg: 02-16-10
07-21-11 12:41 PM - Post#2116474    
    In response to 355Cheyenne

Okay, Thanks...I'll give it a try and see how it turns out.
David

1996 Chevy Z-71
5.7 Vortec 173,000 miles


 
PeteyG708 
Forum Newbie
Posts: 43

Age: 26
Loc: El Paso, TX
Reg: 03-23-11
07-24-11 10:16 PM - Post#2117618    
    In response to davenmer

I can see how that trick would cause concern to inspectors....but it works so wonderfully.

In any case, I picked up a code scanner today. $50 at Autozone, good to have for the future.
Today, I was under the truck inspecting the exhaust. I was very suprised to see that it is all in great condition. There are no holes that I felt in the pipe or the cats, and there wasnt any rust. So its nothing that could be causing a leak, and the cats look great, so I would imagine them to be fine on the inside.

I tried to get the O2 Sensors off, but, of course, I found that I need one essential thing...a proper wrench! The Walmart toolset that I bought almost 3 years ago doesnt carry good tools.

So, with the code scanner, I had 5 codes. the P0420/P0430, a P0452, and the P0420/P0430 Pendings. Cleared the computer and took the truck for a drive. Of course, the light came back on, but when I ran the scanner, it found 4 codes. P0420/P0430 and the P0420/P0430 pending. So I am now thinking that the problem is just those sensors being bad. I checked one of the connectors (pulled it apart and all) and its in great condition. The other one was hard for me to see due to it being inside a box attached to the frame, but I assume its the same thing. All Monitors were on except for 3 (forgot which ones), but I figure (and correct me if I am wrong) that those wont go READY until the P0420/P0430 code clear.

Money is tight, but when I get to get the O2 sensors and a proper wrench to pull em off, I will replace em and let you know.

Oh, and one more thing...check out the following video.

http://www.youtube.com/watch?v=3oc6_y4Z_gA

This is a sound my truck has been making since I bought it. IT doesnt seem to affect anything, as I am still able to drive it with no problems and no loss of power. I did a full tuneup (plugs/Wires, oil and filter, air filter) shortly after I bought it, and it still does it. What could this be?

Thanks!
Pete
------
- 1998 Chevrolet Silverado K1500 Z71 Ext. Cab (Vortec 5700 V8/4L60E 4 Speed Automatic/Push Button 4WD)
- 2002 Ford Taurus SES (Vulcan 3.0L V6/AX4N 4 Speed Automatic)


 
355Cheyenne 
Senior Member
Posts: 3765
355Cheyenne
Loc: Northern MN
Reg: 10-27-04
07-25-11 06:37 AM - Post#2117700    
    In response to PeteyG708

Sounds like a bad serpentine belt tensioner.

P0452 = "Fuel Tank Pressure Sensor Circuit Low Voltage
"
start by making sure your gas cap is on correctly. Could be other things but that is where you would start.
98 Silverado k1500 4x4 350


Edited by 355Cheyenne on 07-25-11 06:39 AM. Reason for edit: No reason given.

 
PeteyG708 
Forum Newbie
Posts: 43

Age: 26
Loc: El Paso, TX
Reg: 03-23-11
07-25-11 02:41 PM - Post#2117846    
    In response to 355Cheyenne

I will see if I can get a better recording of it. if it is the tensioner, would replacing the entire assembly or just the pulley be good? Reason I ask is I just want that sound to stop. $35 for the entire tensioner and bolt isnt too bad.
Pete
------
- 1998 Chevrolet Silverado K1500 Z71 Ext. Cab (Vortec 5700 V8/4L60E 4 Speed Automatic/Push Button 4WD)
- 2002 Ford Taurus SES (Vulcan 3.0L V6/AX4N 4 Speed Automatic)


 
355Cheyenne 
Senior Member
Posts: 3765
355Cheyenne
Loc: Northern MN
Reg: 10-27-04
07-25-11 05:27 PM - Post#2117914    
    In response to PeteyG708

you are going to have to get the complete tensioner replaced.
98 Silverado k1500 4x4 350


 
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