Starts but dies right away

First time poster, short time lurker...

I recently purchased a 2006 TB LS 2wd 4.2 litre straight 6 from a kid that I thought probably didnt have a clue as to how to fix a vehicle. I purchased it of course ,trailered it home, and went to work. Thing is it will start and run for about 3 seconds, then shut off. If you tryi cranking it immediately after this little "running period" its just cranks forever. However, if I wait a few minutes, open the door hit the key switch it will fire right up and die almost immediately. While is is running it sounds fine to me.

I have been a GM guy all my adult life and I normally only buy running vehicles or vehicles that simply need an engine or transmission. This one however is driving me bonkers. If I turn on teh key switch all of teh dash lights go out after a few seconds including teh security light, teh ABS etc. The only light that stays on is the Check Engine light and seatbelt light. Most vehicles I deal with do this same thing.

I have used my code reader on it and it comes back clear.. no errors at all.

My gut feeling is its fuel related , either a clogged or partially clogged fuel filter or a faulty fuel pump.

I have ordered and am waiting on 6 new coils and boots, 6 new iridium spark plugs, the crank and cam sensor, and of course oil and ATF for changing out both. I want it as clean and perfect as possible because I am giving it to my grandson so he doesn't have to drive that freaking ugly ass Pontiac mini van my daughter gave to him. Talk about a junker. Geez...I know hes embarrassed driving that Mom car around. I mean I have a 1996 Z28 being stored in my barn, but thats not going anywhere. Thats one of my toys and of course all of my older grandsons want that car... aint happening.

The truck is in absolutely incredible condition inside and out which Is why Im not giving up. Someone really took great care of this vehicle. It has high miles but it is what it is. I mean I only have 700$ in it, so I dont mind spending a few hundred to make it as close to perfect as I can. The wheels and tires alone are probably worth well over a grand so worst case I part it out and get my money back. I prefer having it on teh road however to be honest.

Thanks guys in advance... I am new here, but not to forums. I build forums and in fact am a computer technician and network engineer but I am semi retired. I run a small one man computer business selling refurbished laptops and desktops and servers, and install long distance wireless networks when I can. However, way before computers became my life I was and still am a fairly competent mechanic, but I do need to get another fuel pressure gauge. I let a buddy borrow mine and it mysteriously was swallowed up by his garage. I am guessing teh fuel pressure gauge will tell me pretty much everything I need to know considering Im finding no faults in other places.

Again thanks....

When it runs and shuts off, does it sputter and die or just shut off like you clicked off the key?

After it dies, if you turn the key off and right back on again (but not start) do you hear the fuel pump prime or not?
I am extremely hard of hearing even with hearing aids. In addition I am mute due to throat cancer. All the radiation treatments screwed up my hearing so thats the reason for the hearing aids..anyway I am going today to purchase a fuel pressure gauge, since my friend has misplaced mine. When it shuts off its just shuts off. If I try to start it back immediately it just spins..nothing at all. After its sits for 30 minutes or an hour or two I can reach in hit the key and again it will fire right up (sounds good) stay running about 3-5 seconds, and then shuts right back off 'I do not hear the fuel pump priming but that could be due to my hearing and I am normally by myself, so I have no second ears per se. I should place my phone on record or laptop with mic and place it close to the gas tank to see if its priming or running at all.. hadn't even thought of that until now. I think the normal pressure range is what 50-57 lbs or so...right?

It is my intention to check the fuel pressure today and I will report back with that. If its normal then I will really be stuck trying to find an answer, and at that point it would almost certainly be one of the sensors I would think.

I already have the fuel filter on order, but held off on ordering the fuel pump simply because there are so many common issues with these 2 and 4WD TBs it seems. I do have new (which I was planning on changing anyway) all 6 coils, boots, and 6 new iridium plugs, along with an ignition switch, as well as the cam and crank sensor.

I just want to make sure its working as perfectly as possible as my grandson takes off for college this fall and i want to make sure he has a fairly solid and dependable vehicle (did I make a bad choice?... probably). .Its just such a good looking SUV. I like the way they look and drive especially, and along with the cheap price is exactly why I bought it.

This new inline 6 is my first experience with this particular Vortec and I haven't seen an awful lot of bad press on teh engines or drivetrains, mostly just electrical or small things that cause huge problems and will nickel and dime you to death,

If all else fails I do have a brand new old style (Carbureted) crate 350 and 700r4 transmission I have been saving. I could simply make a couple of modifications drop it all in the trailblazer and just be done with it. A 1 wire alternator, a 1 wire starter, change the fuel pump, bypass all engine electronics other than what's necessary for normal electrical and be done with it.. At least it would run good and easy to repair. Of course I also have a 350 LS TPI motor I could use as well, that even has the PCM and harness, I just hate spending hours upon hours trying to troubleshoot something and then find out in the end it was nothing but a 50$ part you know... Locally teh cheapest fuel pumps I could find were close to 300 or better, However a really thorough check online and found lifetime replacements (complete pump float o-ring etc) for less than 60$..whats up with that???


Thanks Mooseman for changing the title. Appreciated. And please forgive my rambling from time to time,

A couple more thoughts. Try swapping the fuel pump relay with another in the fuse box. It could be flaky. Fuel pressure regulator, which is built-in to the pump module in the tank, could be suspect too. The fuel pressure tests should give indications of anything going on there.

Although should not be the cause of such a stall, clean the throttle body and reset the PCM by disconnecting the battery for 30 minutes.
How to clean your throttle body

Try seeing if it will start and run on starting fluid. That would definitely point to a fuel issue.

And don't touch the crank sensor unless you are really at that point with nothing else. Doing so will most likely require a CASE relearn by the dealer or someone with a high end scan tool or Tech 2. My gut feeling is that is not at issue. Anything with either of the sensors would throw a code.

For fuel pumps, I recommend only ACDelco or Bosch (same manufacturer). Others have been known to either fail early or the fuel level sender fails. Amazon and RockAuto are good places to look for deals.


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I had similar symptoms and it was a bad fuel pump. If you have 150k+ miles and can't be sure that it was ever replaced, then you are saving yourself from future trouble that could happen at the most inconvenient time. There is a simple brushed motor inside the pump and eventually the brushes will wear out and cause problems in every vehicle.
Connecting a pressure gage to the fuel rail will confirm it - if you watch the pressure drop as the engine dies you'll know.
I am running a low cost pump with a lifetime warranty - it doesn't make sense to spend big bucks on an old truck :twocents: The pump inside the assembly is a standard model used in tens of millions of vehicles - that's why there is a large aftermarket with cheaper replacements. I have a spare pump only that I keep with me when I go on a long trip - just in case.
I take it you are mechanically inclined - in which case you only need to replace the pump inside the assembly and you can save even more. I can send you a link for the exact replacement If you decide to try this.
But do the pressure test first....


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I would add my opinion, if you are giving this as a college car, might as well replace the fuel pump as you are doing so many other items, I'm guessing you'll see pressure problems anyway, so what's one more for the list :smile:
Checked fuel pressure its fine. Between 50 and 60 lbs with key on or when cranking..since it wont start in teh traditional sense of the word, I am presuming the fuel pump is good and teh filter is fine. I have checked every fuse, have ran down every wire and ground, and pretty much went through it without finding anything. 0 codes at all.. nothing ...nada.

From all aspects it should fire right up. I have 6 new coils, 6 new spark plugs, six new boots, a cam and crank sensor as last resorts. Im going to replace teh coils and plugs and bots (wobble bars... ughh) and hope it all just works from that point...after this, I have nothing left that I feel would cause teh problem. I have checked the gas cap even.. and thats getting crazy when I do that :smile:

I have looked for sensors unplugged, wires broken, grounds missing, multi metered it to death and still nothing. Im talking hours and hours of tracing stuff down..still no joy.

Is there anything I could be missing at all?.. Im sure if it were a timing chain etc I would hear it raising hell plus it turns over perfectly so its not like its a timing issue. The kid I purchased it from said he was simply cruising down the road, and it simply shut off and that was it. Never would start back. Never smoked, never made any large noises or bangs, didnt sound like anything broke, it simply just quit and has not fired up since. I checked all dash lights looking for a clue and even the security light on the radio blinks red when the key is at this point I am at a loss because it appears everything, and I do mean everything is working properly.

All I know to do (and Im pretty sure it probably wont work at all..just grasping at straws) is change the plugs and coils and boots and see what happens. I cannot think of anything else at all. Its getting fuel. Only thing left is spark.. I even have a new key switch and door set. I mean I went all out on parts. I have tried it in park in neutral and i have 3 really good batteries. Let it sit for a while, it wil fire up and run for a very few seconds. After that no matter how much you crank it will not even attempt to start,,, let is sit for an hour or so, hit the key, it will run another second or so, and then stop again.

I know it has to be something simple or at least I feel it is, but damned if I can figure it out... if none of this works all I know to do is trailer it, take it to teh GM dealership and let then run their analysis on it but Im pretty sure they won't get any codes either.

Someone asked or assumed earlier I am mechanically inclined.. when it comes to GMs yes absolutely. I have torn down and rebuilt 350s and 400s, TH350s and 700R4s and rear ends, you name it I have done it. I am a computer technician and network engineer, I know how to trace circuits and test everything and for the life of me, this one is simply driving me bonkers.

It should start..period.

Thanks for all the help guys. It is deeply appreciated. Its a head scratcher for sure...Im still listening and looking. I will try anything at this point. I am going out to swap the coils right now on a whim and just to see since the RockAuto box and all pats finally showed up today anyway.

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Got a scanner that can watch cam /crank sensor output to make sure they're reading? I know you said you had the sensors but I couldn't tell if you've put them on yet or not. After you replace the crank sensor you'll get a check engine light until you get to a dealer or someone with a high end scanner to do a crank angle (CASE) relearn.


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I hate telling anyone to replace the crank sensor because it usually doesn't fix anything and requires a CASE relearn.

VATS seems more probable. It has been known to leave people stranded.
Sounds like VATS to me. Starting and immediately cutting out. Everything else checks out...
Have you tried a security relearn?
I have no clue what VATS is and also have no clue as to how to perform a security relearn. Explain please.

This link has the FULL GM OEM Diagnostic Flow Chart... and the Security Re-Learn Procedures list towards the bottom of the page:
Checked teh link and his issue sounds quite a bit different than mine, but teh scan tool I have , I am honestly not certain if it has all of these options built into it. The scan tool I have is around 69$ on average and is for most GMs.. but I purchased it specifically for this TB, I have 3 extremely good batteries and I can run them all down cranking and testing. I usually have one on teh charger and two to test the truck with.

Just a thought, has anyone thought about a bad throttle body?
I have not.. does it even have a throttle boy or is it direct injection??

I have NOT swapped out the cam or crank sensor since I know replacing teh crank sensor is REALLY difficult as far as getting it to work again. I am not sure about cam sensor. Either way neither has been changed, just as I have not replaced teh coils , borts or plugs.

I will be out of town from Thursday this week until Sunday. I am a NASCAR fan, and I have tickets to all 3 races + camping this weekend at Ky Motor Speedway, so the wife and i are camping out, and making a mini vacation out of it...we are leaving early Thursday morning July 11 2018
I have no clue what VATS is and also have no clue as to how to perform a security relearn. Explain please.
Vehicle Anti Theft System. For the security relearn, please see below. :book:

You can install any PCM from a same year truck and it will work after a security relearn, which you can do yourself:

1. Attempt to start the truck by turning the key to the Start/Run position. Try to crank the vehicle.
2. Observe that the vehicle fails to start and the security light is illuminated.
3. Release key to the ON/RUN position (not the ACC position or OFF)
4. Allow the vehicle to sit with key in the ON/RUN position for no less than 11 minutes. Security light will turn off after this.
5. When the light goes off, turn key to OFF position and allow the vehicle to remain in the OFF position for 10 seconds.
6. Repeat #1-#5 for four cycles or until vehicle starts.

That's how I got myself a spare PCM, worked perfectly.
Im missing something here.. as far as codes I have none at all. From every thing I have seen it pure clean with zero codes. This is teh scan tool Im using. I didnt buy mine at Wally World but same I need a different better scanner. I have no problem buying one if that is what I need. The dealership here, Ill be honest, they are not my first choice for performing diags. I can get it there and get it home using my friend and his car hauler..probably cost me 50$ or so. We have two GM dealerships in town.. one is a chevrolet dealer which I never go to and teh other is a GMC dealer which I do trust but is expensive as hell.

My main fear is I will tell them to run teh diags, they will find a simple solution , fix it and then charge me more than what I paid for the vehicle. They did this to me once before on a brake job while i was getting radiation and chemo treatments. I had new rotors lying in teh back seat marked out in big letters Complete rotors for Terrain. Please use. Reason being they had already turned these rotors twice and i was still getting the whomp...whomp of discs dragging on a stop soft or hard,, you could feel it through teh steering wheel badly so I KNEW it needed rotors

They decided to replace the rotors but they ordered and used ACD OEM rotors and ended up charging me 650$ for a 99$ brake job and then were like sorry. My wife had taken it in to be serviced and have teh brakes changed and they basically wrote complete brake job with rotors on the original invoice.. I couldn't argue with them legally.

I had just got out of the hospital with all this cancer crap...and I simply wasn't up to my normal self that would have screamed it from the rooftops especially considering the complete rotors with new bearings etc were right there for them to see. Just kind of pissed me off. Especially since teh brake job we had performed initially and before was a "lifetime warranty" job, however lifetime means for 1 set of brake pads... so every new set past the first one where they replace the pads free, is not lifetime...biggest scam in the world. All over n 11$ set of brake pads... and a 100$ set of bearings and rotors. If I hadnt been so sick at the time I would have done it myself but it is what it is..


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Okay... Without knowing whether or not your Code Reader at some point accidentally cleared the Old Codes... in trying to "Work The Problem"... it takes us right back to The Big Three in Guessing what is wrong:

(1) Air
(2) Fuel
(3) Spark

...that last one...Spark... has possible implications of the cause coming from a Bad Ignition Switch ...but this can only be considered after you have done what @limequat and @Blckshdw have suggested in working through performing the VATS Security Re-Learn Steps... Methodically.

Swapping out the Ignition Switch using a "Parts Shotgun" might make sense... but only If that VATS Re-Learn Procedure does not solve the riddle of the cut-offs. This is because right now... your symptoms have a certain regularity that a mere Bad Ignition Switch would not display if say ....a wire in the steering harness was bad ....or the contacts inside of the switch went sideways. Just keep this component in mind, too a Bad One can cause a myriad of No Start issues.
Vehicle Anti Theft System. For the security relearn, please see below. :book:
Mooseman. I am trying this right now with teh VATS and reset. I am going to work on it late into tonight because at this point its simply making me crazy. Its like when I have a computer that I know is perfect but still wont start up. Its usually a simple answer but this time, its really not as far as this truck goes. I have never had as much trouble getting anything to start, even old junkyard motors... it is just weird.

I haven't swapped teh coils and plugs and boots out if this doesn't work thats my next move. I can send shots of every screen on teh reader but Im not sure it would tell much at all.

Worst case ill go to my buddies and pickup a new PCM.. he has a decent junkyard full of parts, so Im assuming it has to be a 2006 trailblazer or will say a 4wd silverado work etc.. by the way and man do I feel stupid, it IS 4WD system and not a 2wd system. I thought it was 2WD because of what I was told and as far as the title is concerned until I saw the 4WD switch on teh dash. I dont think that would make much of a difference as far as starting but seeing as how i believed it to be 2WD it could be a LOT different. I looked underneath ,, I mean really looked and yeah its 4WD

Stupid stupid me...

When I said "without codes?", I was responding to @smt 59 saying it could be a bad throttle body. It can't be that since this system is very fault sensitive and will throw a code and put it in reduced engine power if there is anything not jiving.

For a dirty or faulty MAF, you could also unplug it and it would run.
Hey Guys,
Thanks for suggestions for real. My friend Jeff is planning on coming over to help me so we will see. I am headed out to Ky Motor speedway for the truck race tonight, and other races remainder of the weekend. Ill be back on Sunday and I will try everything else.We are camping (I should say glamping as much crap as my wife has brought) I have a 2000 watt inverter on my Terrain so I can have electricity etc..depends on where they let us park I guess.

All suggestions will be tried and I sincerely appreciate your guys help...I am hoping something will work.


smt 59

Well-Known Member
When I said "without codes?", I was responding to @smt 59 saying it could be a bad throttle body. It can't be that since this system is very fault sensitive and will throw a code and put it in reduced engine power if there is anything not jiving.

For a dirty or faulty MAF, you could also unplug it and it would run.
Just trying to think outside the box, codes may have been erased by seller.
If there were codes, they certainly hasn't been any with me. Its all clean. Its driving me nuts. I have been gone the past few (man I needed a break) days at KMS watching NASCAR races, so now its back to same old grind. Had to mow lawn before the next T-storm hit.. finished just in time.

Now I think my battery charger has given out as it seems my batteries are no longer charging at all, so I guess Im off to buy another one. I install battery and engine wont even turn over..ding ding ding and lights on dash and then click click. Tried to jump across starter still same click click. Tried battery in another car and sure enough it's just DOA along with the other two that indicate they are charged, according to teh charger, but arent...wally world battery charger. I should have known better after I had to take the first one back for not working. I got the larger , more expensive supposedly better one same brand, now its doing practically teh same thing as the cheaper one... just wont charge at all..

I went through the electrical where the idiots removed the aftermarket alarm system, cannot find any dead shorts or anything that looks out of place according to wiring diagrams, new ignition switch and everything I can trace with a meter comes back clean. Scan of course tells me zilch.. like nothing is wrong at all. Of course without it running I will never get an error code anyway I suppose.

Frustrating to say the least. I am going to pull the breather assembly tomorrow The cover over teh plugs and coils and throttle body I guess), swap out all of the plugs and coils since I have them here and steal a new battery out of my Terrain that I know is good while the others are on the charger. I have a cam sensor and crank sensor but am hesitant to change either of those at all.

This has been about the craziest and weirdest and most frustrating thing I have ever been through with any GM vehicle. Its hard to believe that something where you can find nothing wrong will simply refuse to start and run. Makes absolutely no sense to me. I have spark, I have fuel, I have air... go figure.

And thanks so much to everyone here who has input anything or helped or discussed in any way. At this point Im willing to try almost anything. I know it's going to end up being something simple or weird and that's really going to piss me off.

That's usually how it is with these sorts of things. Something stupid simple is the culprit, the last thing you'd think to look at. Makes you just wanna go :duh:

Here's hoping you find it quickly. I'm really not sure what to think.


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