Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum banner

1 - 20 of 22 Posts

·
Registered
2006 chevy trailblazer_ls_ext
Joined
·
57 Posts
Discussion Starter #1
OK...before I get a "did you search the forums" response, I did. I'm just looking for a little advise and expertise that I do not have.

When I bought my 06 Trailblazer, the CEC light was on durring the test drive. The dealer told me it was an O2 sensor and they were going to replace it. The fuel guage did not work, so they replaced the sending unit. Wehn I picked it up from the dealer, the CEC light was off and the fuel guage worked fine. The CEC light came on two days later. I had it checked at Autozone (can't remember that particular code), consulted the collective brain of Trailvoy and determined it was a dirty throttle body. I had the dealer clean the throttle body and the CEC light stopped. A couple days later I get code p0171. At this point the light would come on and go off about every two days or so.

I changed the O2 sensor at the engine last night, since that seemed to be the first option suggested by most of you. I diconnected the battery and all was good. My wife started it this morning and she said it sputtered for a few seconds after startup which it has never done before. After about a mile or two of driving the CEC light came back on with the p0171 code again.

Any suggestions on what I should do next, realizing that I am not a skilled mechanic, but can do minor repairs. Should I try to clean/replace the MAF sensor? Could it be the O2 after the CAT? Any help would be great. If I have to take it in to a shop I will, but I'd like to do what I can first.

Thanks!!
 

·
Registered
2004 chevy trailblazer_lt
Joined
·
1,298 Posts
Here's a few ideas, borrowed from another thread (http://forums.trailvoy.com/showthread.php?t=74529&highlight=P0171), post by tricguy007,and modified slightly (bearing in mind that his was for an 03):

1. Check for a skewed Engine Coolant Temperature (ECT) or Intake Air Temperature (IAT) sensor by making sure that they are within a few degrees of each other prior to a cold start. If one of the sensors is skewed, replace it.

2. Inspect for obvious vacuum leaks at the throttle body, intake and Positive Crankcase Ventilation (PCV) hose between the #3 and #4 intake runners. If there are no vacuum leaks found, remove the throttle body and inspect the throttle body gasket to make sure that it is not rolled. A rolled seal could cause an intermittent or hard to find vacuum leak. If the throttle body gasket is rolled, replace it. Since the dealership supposedly worked on the throttle
body, I'd definitely check the area around the throttle body for loose hoses,
wiring, or perhaps the throttle body gasket being misaligned.

3. Clean the fuel injectors using the procedure found in TSB 03-06-04-030. If cleaning the fuel injectors corrects the concern, refer to TSB 04-06-04-051A, which relates to maintenance cleaning of the fuel injectors to prevent a reoccurrence. Also, make sure that the customer is using gasoline from a high quality, high volume filling station. Go for a Seafoam clean or put some Techron in your tank and see if it improves.

4. Inspect the Oxygen (O2) sensors for contamination. If contaminated, isolate the reason for contamination by inspecting for contaminated gasoline, coolant consumption or previous repairs where silicone may have lead to the O2 contamination. If a concern is found, repair the cause for contamination as necessary.


Are you sure the dealer cleaned behind the throttle butterfly? Often, they'll
just jet some cleaner through, but that doesn't always get the buildup behind
the plate.

What brand of O2 sensor did you use?

Probably couldn't hurt to at least try to clean the MAF sensor.

Could also be that the clean the dealer did put so much crud through
the system that it caused buildup, but if that was the case, I'd expect the
new O2 sensor to behave better...unless it's an off brand.

Good Luck!

Chris
 

·
Registered
2006 chevy trailblazer_ls_ext
Joined
·
57 Posts
Discussion Starter #3
Thanks for the reply. It looks like I need to get a repair manual because I have no idea where the two sensors are in item 1. but I will find out. I plan on taking things apart and looking for disconnected hoses and such. I was hoping not to have to remove the throttle body, although it seems pretty easy. I'll do it if need be. Where does one find TSB 03-06-04-030 and is that something I can do with limited mechanical experience?

As for the O2 sensor. The one I removed was dark in color with white residue looking marks around it. I call it residue because that's what it looked like, but it would not wipe off with a dry cloth. I replaced it with a bosch brand sensor.

What would one use to clean the MAF?

Thanks
 

·
Registered
2006 chevy trailblazer_ls_ext
Joined
·
57 Posts
Discussion Starter #4
So...I started with the easiest and cheapest of the options. I removed and cleaned the MAF sensor with MAV Sensor cleaner. The wife has driven the TB all day and the CEL has not come back on...that is a good sign. I did notice that one of the screws holding the MAF in place was a little looser than I thought it should have been. Maybe it was loose enough to cause the sensor to be slightly off center from where it should have been...or maybe it was just dirty??

With my luck, the light will come on tomorrow...:hissy:
 

·
Registered
2004 chevy trailblazer_lt
Joined
·
1,298 Posts
Pretty much anything listed as sensor safe should be OK.

Loose sensor could easily cause a problem.

We'll hope that's the cure, but keep some of the other things
in mind....y'know....hope for the best, prepare for a PITA.... ;)
After all, Murphy loves auto mechanics... ;)

Good Luck!

Chris
 

·
Registered
2002 chevy trailblazer_ltz
Joined
·
170 Posts
Ok, just my :m2: here, and since you didn't post today, I'll assume the CEL didn't come back on today like you assumed, however, maybe my experience will help others who stumble upon this thread...

I bought an Audi TT this time last year with a CEL on and the previous owner told me "It came on when we put the K&N on it", so me, being naive (aka, stupid) believed him. Looking back, K&N isn't known for putting out products that cause CELs, but oh well. I had the code scanned and it was P0171 - Lean on Bank 1, and I'm hoping this code is the same for our TVs, or else my experience is pointless.

I cleaned the MAF with no luck, then replaced it ($300) with no luck, then had a misfire form, so I replaced all 4 spark plugs and coil packs (~$250) which fixed the misfire, but not the P0171. Four months later, and still no luck removing the code, the car was still improperly licensed :)weird:) because I couldn't pass inspection with a CEL that seemed to not do anything but cause a light in the dash since everything else seemed to be working fine.

One day, before a cruise I was going on with a group of VWs, I went to Autozone and bought $17 worth of junk. Their reward card system is set up to give a point each time you spend $20 or more and you get a free $20 after earning 5 points. I didn't want to waste my $17 purchase for no points, so I bought the first thing within reach which was a bottle of fuel injector cleaner "recomended with each oil change", so I bought the bottles and threw them in the back seat. Before the cruise, I filled up with gas and dumped a bottle of injector cleaner in the tank. I spent the next 4 hours or so "cruising" ("spirited driving") down backroads WAY too fast, and racing other cars (stupid...) before finally heading home. I made it to the last light before my house and got stopped. When I took off, I floored it and the car fell on its face hard, the CEL started flashing like it was a misfire, then everything went back to normal, the engine revved back up, the CEL turned off and I parked the car, but still with no CEL. I drove it for a few days, still with no CEL, had it inspected, which it passed, and it never messed up again. When I mentioned this to a few older "car guys", they told me that's how lean codes used to get fixed at dealerships: A bottle of fuel system treatment and a "spirited drive" around the block usually cleared things up. After $500+ in attempted fixes, it was a $4 bottle of injector cleaner and aggressive driving that I'm guessing dislodged a clog in one of my injectors. :confused:

Maybe someday someone will stumble upon this and try out injector cleaner and it will work before spending mucho :m2::m2::m2: on failed attempts to fix P0171.
 

·
Registered
2004 chevy trailblazer_lt
Joined
·
1,298 Posts
Yep. That's why Seafoam and Techron are both mentioned in part 3 of post #2.
Either one is listed as an injector cleaner as applied to the fuel system. :)

Definitely an inexpensive way to at least eliminate one possibility.

Cheers-

Chris
 

·
Registered
2006 chevy trailblazer_ls_ext
Joined
·
57 Posts
Discussion Starter #8
Thanks for the suggestions. About 5 minutes after my last post, my wife came home to inform me that the CEL had come back on. We were out the door for a weekend camping trip so I didn't have time to post it.

I did put a bottle of Lucas injector cleaner in there, but maybe I should try the Techtron or Seafoam. I'd been reading about seafoam on here and thought maybe I should do that. Any preferences? Would the Lucas be enough or would one of the others be "better"....whatever that means?

My next course of action is to take the air box and related things off and check for any vacum leaks. I'll probably take the trottle body off and inspect the seal there too.

What kinda sucks with this is that the truck seems to run perfectly fine. I'm guessing that's because the computer has detected something off, but it's probably not off by much...... Just enough to trigger the CEL. I don't want to drive it too much with the light on though.
 

·
Registered
2004 chevy trailblazer_lt
Joined
·
1,298 Posts
Sorry the CEL came back!

Just for the sake of being thorough, did you actually scan the
codes again and get the P0171 *this* time?

Seafoam seems to be the most complete treatment for oil, fuel
and vacuum systems. Techron mainly covers fuel affected areas.
At least that's my impression.

In many cases, as long as the CEL isn't flashing, it's OK to drive
the vehicle a bit. Obviously you don't want to drive it with something
failing, but if it's something like the P0128 thermostat error, you can
at least still get around if you *needed* to.

Cheers-

Chris
 

·
Registered
2006 chevy trailblazer_ls_ext
Joined
·
57 Posts
Discussion Starter #10
I haven't taken it in to get scanned yet. I'm doing that tonight. I don't own a scanner, but apparently I should invest in one.

I'll try the complete seafoam treatment this weekend. I'm due for an oil change so now is the time for that. I'll do the vacume system and the fuel system while I'm at it. I'm sure it's never been cleaned like that anyway.

I'll keep at it and report on here what I find and what actually fixes this thing. Maybe it will be helpful to others as this seems to be a fairly common error code.

Thanks!
 

·
Registered
2006 chevy trailblazer_ls_ext
Joined
·
57 Posts
Discussion Starter #11
Well, the CEL went off yesturday. Maybe it was the Lucas injector cleaner? If history repeats, the light will be back on in a day or so. I'll keep you posted.
 

·
Registered
2008 chevy trailblazer_ls
Joined
·
101 Posts
I got P0171 today too lean condition.
Techron +Sunoco high test shut the light off within 10min. Hopefully I won't have to mess with it further. Autozone had a 2 for one price on Techron so grab some if anyone sees this during the sale period. :iagree:
 

·
Registered
2006 chevy trailblazer_lt
Joined
·
50 Posts
I had this same thing happen on my '05 Grand Prix. Replaced wires and plugs, coolant temp sensor, cleaned the MAF, fixed a few small vacuum leaks, ran tons of SeaFoam through tank and intake at various times, and replaced all the O2 sensors. Finally after all this it turned out to be the catalytic converter. They are hard to diagnose and probably why the "sprited drive" of the other poster fixed his problem (heated the converter up enough to burn out whatever crud was causing the problem). Just a consideration.
 

·
Registered
2005 chevy trailblazer_ls
Joined
·
372 Posts

·
Registered
2006 chevy trailblazer_ls_ext
Joined
·
57 Posts
Discussion Starter #15
p0171.......now a misfire.....

UPDATE...

I still haven't fixed the p0171 code. I finally broke down and took it to the shop today. This morning my wife was ready to take the kids to school and as soon as she pulled away from the house, the CEL started blinking and then stoped (but stayed on) and the TB was totally nonresponsive. She said it idled rough and just putted along. She put the pedal to the floor and nothing. The engine didn't even attempt to rev. She turned around to bring it back home. About a 1/2 block from the house she said it just started working again. I went home and swapped out cars. It started and ran fine for me, except the CEL was still on, which is nothing new. I took it to Autozone and all they found was the p0171 error. There was no misfire code! Does that sound right? Needless to say I drove it straight to the shop!

I'll let you know what they tell me.
 

·
Registered
2006 chevy trailblazer_ls_ext
Joined
·
57 Posts
Discussion Starter #16
Let me run this by the collective brain that is Trailvoy.com...


I've been reading about misfires lately, specifically about this water seal issue with Cyl #4. As I was thinking about that, it occurred to me that it rained here last night, possibly for the first time since I got my TB. It's parking in front of my house which sits on a hill so the front sits lower than the rear. If water would have gotten in around the coil, could that explain why the first run of the day produced the misfire. Additionally, if all of the water would have evaporated out because of engine temps before my wife made it home, would the TB have started running properly? By the time I got home, there would have been no misfire because there would have been no water to create the arc. Am I on to something here? All I know is the garage is still trying to track down the problem.

This would not be the cause of my p0171 error......would it?
 

·
Registered
2006 chevy trailblazer_ls_ext
Joined
·
57 Posts
Discussion Starter #17
UPDATE...

(I realize by now I am simply talking to my self in this thread, but hear goes......)

The shop has isolated the problem to the intake. They have been able to determine that I have a faulty gasket or a cracked intake or similar and that air is entering the engine in that vicinity and causeing the p0171 code. They are digging into the TB now to determine the exact cause and the $$ to fix it. Hopefully not a very $$ fix for my sake...:worried:
 

·
Registered
2004 chevy trailblazer_lt
Joined
·
1,298 Posts
You're not just talking to yourself, just that you're providing more
info than we already had. Some of us are watching and want to see
what happens!

From what I've seen in the manuals, the intake gaskets are something
you could probably do yourself, but it's probably not something you'd
want to do on a guess (and I should probably stop using the word probably
so much... ;) ).

Thanks for keeping us updated!

Cheers-

Chris
 

·
Registered
2006 chevy trailblazer_ls_ext
Joined
·
57 Posts
Discussion Starter #19
Chris,

I just hope they figure it out. It's been the shop for two days before he called and said "we idolated the general area of a leak. We need to tear it apart a little to find it." I should know by tomorrow.

Do you think my water theory above make sence? I can't imagine the intake leak would have caused a misfire condition....maybe I'm wrong?
 

·
Registered
2006 chevy trailblazer_ls_ext
Joined
·
57 Posts
Discussion Starter #20
Bad intake gasket(s). All better now.:) $370ish. Which is not too bad concidering they had it for 3 days because the leak was small and hard to find......at least that's wha they said.
 
1 - 20 of 22 Posts
Top