# 01 Z71 issues



## shallowsport702 (Dec 11, 2007)

Recently my service engine soon light has randomly been coming on and staying on for awhile, and then eventually turning off. What I have been experiencing is while I'm driving, either at low speeds or on the highway, my truck will kind of hesitate, to where I feel a slight bump out of nowhere. It will do that sporadically but it's not when the vehicle is shifting so I don't think it's a transmission issue. I was thinking it's something more along the lines of a timing issue. Also, when I first start my truck in the morning and back it out of the driveway, once I put it in gear the truck sputters like it wants to die and once I give it some gas and start going it's fine. I just had the fuel pump replaced recently so I'm not too sure what that problem could be. Any help would be appreciated. Thanks in advance


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## Jeepmanmike (Aug 17, 2005)

Next time it comes on get to the closest autozone or whatever auto parts place you go to. Go inside and ask to use there diagnostic computer, the plug should be under your dash on the left side, it will run the codes and tell you what is going on. I had a check engine light come on in my 4runner a couple weeks ago did the same thing went to autozone turned out to be a O2 sensor.


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## shallowsport702 (Dec 11, 2007)

Jeepmanmike said:


> Next time it comes on get to the closest autozone or whatever auto parts place you go to. Go inside and ask to use there diagnostic computer, the plug should be under your dash on the left side, it will run the codes and tell you what is going on. I had a check engine light come on in my 4runner a couple weeks ago did the same thing went to autozone turned out to be a O2 sensor.


I've tried taking it to autozone when it comes on, but when they plug it in nothing happens, their machine they use doesn't light up like they say it should, and they always end up telling me something is wrong with my computer port. I don't think that's the case because the dealership has no problem reading the codes, I just don't wanna pay $80 to pay them to do it.


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## 6.5 shooter dude (Jan 8, 2008)

shallowsport702 said:


> I've tried taking it to autozone when it comes on, but when they plug it in nothing happens, their machine they use doesn't light up like they say it should, and they always end up telling me something is wrong with my computer port. I don't think that's the case because the dealership has no problem reading the codes, I just don't wanna pay $80 to pay them to do it.


Chances are you have a blown fuse, change out the fuse and go back to autozone and get codes pulled, and than report the codes on here do not buy anything from them at that point.


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## shallowsport702 (Dec 11, 2007)

Capt Jay Baker said:


> Chances are you have a blown fuse, change out the fuse and go back to autozone and get codes pulled, and than report the codes on here do not buy anything from them at that point.


Where would the fuse be located and which fuse would it be?? Would it be the PCM fuse?


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## shallowsport702 (Dec 11, 2007)

Capt Jay Baker said:


> Chances are you have a blown fuse, change out the fuse and go back to autozone and get codes pulled, and than report the codes on here do not buy anything from them at that point.


Found it, the CIGAR fuse was blown..I'll take it back and post what codes come up, thanks again Jay.

p.s. You ever sell your Harley? I went over and checked it out, my name is Rick, I was driving the white Z71 (which is the subject of this post)


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## gulfcoastpunk (Feb 14, 2005)

I woud go with either fuel pressure regulator or intake gasket leak


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## Critter Catcher (Mar 25, 2005)

As far as the stuttering issue goes on cold starts, try cleaning the throttle body. These vehicles are notorious for erratic idle due to a dirty throttle body. Once you get the codes post them and we'll go from there on the other.


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## shallowsport702 (Dec 11, 2007)

Now that I've replaced the fuse to be able to get codes from the computer port, I can't get the dang Service Engine Soon light to come on!!! I know, how convienient..It's still doing the bump/hesitation while on the highway, but what I wanted to know was, if I take it to autozone and plug in their tool, will it give the last codes that have come up, or does the S.E.S. light have to be on when they plug it in. I've heard yes and no, yes from the autozone guy who kinda sounded lazy like he didn't wanna go outside and plug it in, and no from a mechanic who I happened to help out at my job. Once again, any help would be appreciated. Thanks in advance.


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## Critter Catcher (Mar 25, 2005)

It is very possible that it will story it in HISTORY codes. The only way to tell is to plug it in.


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## shallowsport702 (Dec 11, 2007)

Just thinking out loud here, but do any of you guys think it could have anything to do with the knock sensor? The only reson I ask is that because when I purchased the truck at 76,000 miles (it now has 173,000), within a few days of me having it the Service Engine Soon light came on. Took it back to the small dealership where I got it and they plugged in the diagnostic tool and the knock sensor code came up. They insisted it wasn't a big deal and deleted the code,and I didn't have much of an argument for them to replace it being as I declined the extended warranty. Now everything has been pretty good up until this point, and I've heard about these trucks having poor seals for the knock sensor and them getting corroded, so my question is, could what I'm experiencing while driving be an engine ping/knock due to bad knock sensor(s)?


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## tx-fisherdude (Dec 4, 2005)

When was the last time you changed plugs? Check your fuel pressure regulator its on your intake manifold with a vacuume hose going to it. Pull the hose and if gas comes out of it replace it (the regulator not the hose)


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## CAJUN THUNDER (Sep 6, 2006)

gulfcoastpunk said:


> I woud go with either fuel pressure regulator or intake gasket leak


intake gasket's leaking will not cause it to come on....i bet it's a o2 sensor..


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## shallowsport702 (Dec 11, 2007)

Fisherdude, I changed plugs about a month and a half ago. I actually swung by autozone today after work and asked the guy to plug in the diagnostic tool for me, which he didn't really care to do since the service engine soon light was not on at the moment, but tried anyway, and sure enough it threw out the lean bank 1 and lean bank 2 codes, or something along those lines( I didn't get a chance to write down the codes). The guy said that when it's just one of the codes I mentioned, it's the O2 sensor, but when it's both the codes I mentioned, it's mass air flow sensor. Does this sound right? I hate to spend $140 on a mass air flow sensor when that's not the problem. Thanks again.


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## wave hopper (Dec 27, 2004)

when the check engine light comes on it means you have something wrong with the emissions o2 sensor,gas cap something along those lines best thing to do is get the codes and google them to see what they are i just went through the same thing with an 2006 chevy


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## tx-fisherdude (Dec 4, 2005)

Do you run a K&N filter I read that these can get oil on the mass air flow sensor. They do sell a cleaner for cleaning these its a CNC brand. Dont know if it will work but its worth a shot.


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## shallowsport702 (Dec 11, 2007)

tx-fisherdude said:


> Do you run a K&N filter I read that these can get oil on the mass air flow sensor. They do sell a cleaner for cleaning these its a CNC brand. Dont know if it will work but its worth a shot.


Actually I do have an Airaid intake system. Today I took it all apart and cleaned up the throttle body and while I was at it cleaned and oiled the air filter. Would I notice oil buildup or gunk on the mass air flow sensor, because it looked fine and clean today when I unplugged it and checked it out.


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## Maritime (Aug 28, 2007)

I had an '02 Z-71 that i recently sold that had similar problems. I had to change the fuel pump 3 times before i got a good one, so don't think it can't be the same problem. Also you should try and take it to a mechanic and get a fuel pressure reading. I think the pressure should be around 55 psi anything less will trigger the codes. My truck was sending the same codes... lean bank 1 and 2. So before you drop any money get a PSI reading, it shouldn't take more than 5 min.
P.S. The 55 psi is just a guess. The mech. should have a book with all the numbers for ya.
Good luck, my truck gave me hell.


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## shepard24 (Jul 16, 2006)

sell it



j/k


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## shallowsport702 (Dec 11, 2007)

shepard24 said:


> sell it
> 
> j/k


Carl, don't think the thought hasn't crossed my mind. I'm gonna sell in or around April...I'll sell the truck and use my tax refund on a newish one. Hopefully I'll get more for mine than you did for yours.


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## BROWN (Jan 8, 2006)

shallowsport702 said:


> Fisherdude, I changed plugs about a month and a half ago. I actually swung by autozone today after work and asked the guy to plug in the diagnostic tool for me, which he didn't really care to do since the service engine soon light was not on at the moment, but tried anyway, and sure enough it threw out the lean bank 1 and lean bank 2 codes, or something along those lines( I didn't get a chance to write down the codes). The guy said that when it's just one of the codes I mentioned, it's the O2 sensor, but when it's both the codes I mentioned, it's mass air flow sensor. Does this sound right? I hate to spend $140 on a mass air flow sensor when that's not the problem. Thanks again.


You should be able to get an actual code off of the reader. Once you get the code you can find a website that will tell you what it means. Like this site. http://www.aa1car.com/trouble-codes/codes_699.htm


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## Critter Catcher (Mar 25, 2005)

Sell it to me. I'll take that POS off of your hands.


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## shallowsport702 (Dec 11, 2007)

Critter Catcher said:


> Sell it to me. I'll take that POS off of your hands.


Easy there critter, me and this ol' gal have been through alot. She's taken care of me for about 100,000 miles so far and is beautiful inside and out, but I will say, she's being a bit of a ****** right now. Once we get this minor issue taken care of, she'll be as good as new again.


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## Critter Catcher (Mar 25, 2005)

I was just messin' with you man. Those are great trucks.


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## [email protected] (Dec 2, 2008)

is your truck losing water?


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## shallowsport702 (Dec 11, 2007)

Critter Catcher said:


> I was just messin' with you man. Those are great trucks.


Yea I know, I was just kiddin around too


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## shallowsport702 (Dec 11, 2007)

[email protected] said:


> is your truck losing water?


Yea, but I just figured it was because of the A/C..Why do you ask?


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## shepard24 (Jul 16, 2006)

shallowsport702 said:


> Yea, but I just figured it was because of the A/C..Why do you ask?


intake gasket????


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## shallowsport702 (Dec 11, 2007)

shepard24 said:


> intake gasket????


Would that be the gasket where the exhaust pipe meets the intake manifold?


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## shallowsport702 (Dec 11, 2007)

Just got the diagnostic codes, PO171 and PO174, went to the website that tells what they are and I'm not too sure what they mean.


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## 6.5 shooter dude (Jan 8, 2008)

Water does not circulate through the intake on a 5.3L that is not going to cause lean issues like po171-po174. My first guess would be dirty fuel injectors and plugged fuel filter, feel free to call me with any questions.......Jay


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## texasfisherman (Mar 9, 2007)

*ya'll are slaying us...*



shallowsport702 said:


> Would that be the gasket where the exhaust pipe meets the intake manifold?


 ....ya'll gotta keep this diagnostic going. We're just four bored mechanics sitting around on a slow afternoon. This is very entertaining. Seriously, and I'm not trying to be rude, but if you think the intake manifold is connected to the exhaust pipe you need to do your truck a favor and pay the $80 for a real diagnostic test. Then put a padlock on the hood and give the key to your mechanic.
Lean and rich fuel mixture codes are very general (non-specific) codes and can require alot of things to be checked before you find the fault. It is not the kind of code that pops up and says "replace this part". Very few codes are that descriptive. Good luck. I really do hope it dosen't cost you an arm and a leg to repair this thing but ya'll need to understand that what AutoZone does is not diagnostic. They pull the code and give you a list of possible causes (which they would love to sell you the parts for). Also understand that the list of 3 possibles is not all the possibles.
P.S. For all you guys out there running K&N and other "oiled" air filters you are just asking for lean codes resulting from a contaminated MAF.


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## shallowsport702 (Dec 11, 2007)

texasfisherman said:


> ....ya'll gotta keep this diagnostic going. We're just four bored mechanics sitting around on a slow afternoon. This is very entertaining. Seriously, and I'm not trying to be rude, but if you think the intake manifold is connected to the exhaust pipe you need to do your truck a favor and pay the $80 for a real diagnostic test. Then put a padlock on the hood and give the key to your mechanic.
> Lean and rich fuel mixture codes are very general (non-specific) codes and can require alot of things to be checked before you find the fault. It is not the kind of code that pops up and says "replace this part". Very few codes are that descriptive. Good luck. I really do hope it dosen't cost you an arm and a leg to repair this thing but ya'll need to understand that what AutoZone does is not diagnostic. They pull the code and give you a list of possible causes (which they would love to sell you the parts for). Also understand that the list of 3 possibles is not all the possibles.
> P.S. For all you guys out there running K&N and other "oiled" air filters you are just asking for lean codes resulting from a contaminated MAF.


I think it's quite obvious that I'm not a mechanic, and I actually meant the exhaust pipe to (exhuast)manifold gasket, but going back to your post..I know there are alot of mechanics and people with alot of mechanical knowledge on here, which is why I'm asking these questions. If money wasn't an option, I would do just what you said, take it to a mechanic or dealer, but money is an option, which is why I haven't. The thing with that is, if I take it somewhere and it's something that can be fixed in 30 minutes, and was fixed in 30 minutes(give or take), when I go back to pick up my truck my receipt says 2 hours labor. At $70 an hour, that hurts. Now I know there are very good mechanics and very honest mechanics out there, so this is not an insult to anyone, I'm just sayin it would be nice to be able to find out what the problem is and purchase the part online(so I don't get ripped off with that too), and if the installation is too difficult, take it to a mechanic for installation. I know what my limitations are and I'm not gonna start taking my truck apart. This is my only mode of transportation so I can't afford to be without a vehicle.


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## texasfisherman (Mar 9, 2007)

My point was if you take it to someone it is going to be cheaper in the long run than you buying parts that you dont need to fix your problem. You may get lucky and stumble onto the problem and fix it the first time but all its going to be is luck.


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## lonestarcowboy (Nov 24, 2006)

i am a professional  mechanic, my father and I own a shop which my father started 16 years ago,

Trouble codes PO171, PO174 are as you thought lean codes. Can be caused by a vacuum leak, fuel pump, fuel pressure regulator, and several other things. These codes are time consuming to find are even harder when they are intermittant. Without the proper tools your will never find this problem. Until you take it to someone who does you are wasting time, money and effort.


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## shallowsport702 (Dec 11, 2007)

Sprayed some throttle body cleaner on the intake gaskets while the engine was idleing and the idle roughed up a bit, happened when I sprayed it on both sides. So I guess that's it, need to replace the intake gaskets. At least that's my next step. Thanks for all the info and help, it's much appreciated.


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