New member need help Trailblazer keeps cutting out

[joeytreats]

Hey Everybody,

I have a 2003 trailblazer and while driving it will cut out and wont restart for hours after the fact. I just changed the fuelpump and the fuelfilter after speaking with the service center manager in my area. It did not work. At times I can drive the car for days or weeks with no problems. Suddenly while driving it will just stall and will not restart. I am over the warranty period. Could this be an electrical problem? Could it have anything to do with the ignition switch? The car seems to die on local roads doing between 30 and 40 mph. I have looked thru theforum and have seen everything from egr , to fuel pressure and ignition switch. Please help i cant afford to keep getting the car towed.


Ok I got a code uf1000, the fuel pump is shutting off after it initially starts. I have manually over ridden the relay so i can use the car for short trips. Seems to be a Computer Problem. At this point am I better off taking it to a dealer ? Thanks for the past help and any additional help is greatly appreciated.

[joeytreats]

Originally Posted by joeytreats

Hey Everybody,

I have a 2003 trailblazer and while driving it will cut out and wont restart for hours after the fact. I just changed the fuelpump and the fuelfilter after speaking with the service center manager in my area. It did not work. At times I can drive the car for days or weeks with no problems. Suddenly while driving it will just stall and will not restart. I am over the warranty period. Could this be an electrical problem? Could it have anything to do with the ignition switch? The car seems to die on local roads doing between 30 and 40 mph. I have looked thru theforum and have seen everything from egr , to fuel pressure and ignition switch. Please help i cant afford to keep getting the car towed.

Can Any1 Help Me?

[ScarabEpic22]

Sorry, no ideas.

[blazer94]

No codes have been thrown? Is your service engine light flashing, or did it ever during these periods? Have you done any electric mods, like amp, fogs, etc? Before they replaced the fuel filter/pump, did they check the battery, alternator, engine and frame grounds? Any recent engine work done? Gotta start somewhere, dont let the dealership keep throwing parts at it, that gets mighty expensive...even with the description of juust cutting out, I'd think they could run a diagnostic and check the electrical / charging system.

[GMMerlin]

Gotta start somewhere, dont let the dealership keep throwing parts at it, that gets mighty expensive...even with the description of juust cutting out, I'd think they could run a diagnostic and check the electrical / charging system.

If you read his post, you will see that he is doing the work..don't go slamming the dealer...

Some things to think about here, does it stall quickly or die out slowly..are any other systems effected.
You are developing a pattern that may help in the diagnosis process, but one thing to remember is intermittant problems are difficult to diagnose.
I would check for codes and if the vehicle readily restarts or does it take a while before it will start and run..if so, check for fuel and spark.
I wouldn't throw an ignition switch at it just yet, but it is a suspect.

[blazer94]

Originally Posted by GMMerlin

If you read his post, you will see that he is doing the work..don't go slamming the dealer...

Some things to think about here, does it stall quickly or die out slowly..are any other systems effected.
You are developing a pattern that may help in the diagnosis process, but one thing to remember is intermittant problems are difficult to diagnose.
I would check for codes and if the vehicle readily restarts or does it take a while before it will start and run..if so, check for fuel and spark.
I wouldn't throw an ignition switch at it just yet, but it is a suspect.

Hmmm, Didn't mean to appear to slam the dealer, I figured if he talked to the service manager, these other ideas might have come up before dropping a gas tank to replace a fuel pump. The idea of checking for other spark /fuel issues is probably the better idea... if you (he) are doing the work yourself, I do understand how frustrating tracing down an intermittent problem can be. We still don't know if he has had codes, check engine, etc. Joeytreats, if there is any way you could check your charging system, spark and fuel that may be a good place to start. Good luck.

[joeytreats]

Originally Posted by blazer94

Hmmm, Didn't mean to appear to slam the dealer, I figured if he talked to the service manager, these other ideas might have come up before dropping a gas tank to replace a fuel pump. The idea of checking for other spark /fuel issues is probably the better idea... if you (he) are doing the work yourself, I do understand how frustrating tracing down an intermittent problem can be. We still don't know if he has had codes, check engine, etc. Joeytreats, if there is any way you could check your charging system, spark and fuel that may be a good place to start. Good luck.

There are no warning lights and no codes as well. While driving it will just cut out and will not restart for about 12 hours. I have the ignition switch and will be changing it tomorrow part only cost me 21 dollars. The car will just stall and it dies right away. When trying to restart it will just keep attempting to turn over but nothing. No recent work has been done on the car, except the fuel pump and filter last week.

[joeytreats]

Ok I have a code it is uf1000. The relay to the fuel pump is cutting out. I have manually over ridden it for now. Seems like a computer problem. Am I better off bringing it to the dealer at this point? Thanks for the halp.

[blazer94]

I don't have much experience with replacing relays.
Perhaps if you know of a trusted mechanic locally where you live, they could replace the relay. Here is a link to A GM online parts dealer, cost is about 12 bucks for the relay.
https://www.chevygmparts.com/oe_parts_catalog.html
(enter your vehicle info, than drill down thru the fuel system and fuel supply to get to the relay)

If you were able to bypass the relay, you could probably replace it, too. Good Luck

[joeytreats]

Originally Posted by blazer94

I don't have much experience with replacing relays.
Perhaps if you know of a trusted mechanic locally where you live, they could replace the relay. Here is a link to A GM online parts dealer, cost is about 12 bucks for the relay.
https://www.chevygmparts.com/oe_parts_catalog.html
(enter your vehicle info, than drill down thru the fuel system and fuel supply to get to the relay)

If you were able to bypass the relay, you could probably replace it, too. Good Luck

The relay is not the problem. It is not getting a signal apparently to turn on. Perhaps the moderator can help me out. Thanks for the input though.

[GMMerlin]

Originally Posted by joeytreats

Ok I have a code it is uf1000. The relay to the fuel pump is cutting out. I have manually over ridden it for now. Seems like a computer problem. Am I better off bringing it to the dealer at this point? Thanks for the halp.

The U1000 code is a communication code. This means that a module is not communicating with the others.
Since you say you have overidden the relay, I'll assume that you went from B+ to the pump side of the relay.
On the control side, the PCM supplies 12volts to the relay to energize the coil.
The PCM B fuse supplies power to the fuel pump as well as the PCM and is the only no switched power source to the PCM.
If you do not have 12volts on the PCM B fuse, then you have an issue from the battery to the underhood fuse block or an internal failure of the UBEC (fuse block)
There are 4 fuses that supply switched ignition to the PCM.
PCM 1,ETC/TAC and the IGN E fuses are located in the UBEC. If there is low or no voltage there, then you have an ignition switch failure (which you should see other systems not operating properly)
The IGN 2 fuse is located in the fuse block under the left rear seat and is powered by the ignition switch also.
Any failure on these circuits will cause a stall and no start concern and the communication code.
If you have the capability to communicate with the BCM, you can check power moding and this will tell you if the ignition switch is powering the modules.
There are 2 circuits in your relay.
First one is the control circuit. PCM supplies 12v to the solenoid and the solenoid is grounded thru the chassis.
Second circuit is the pump circuit. 12v is supplied from the PCM B fuse and the ground is supplied thru the pump to chassis ground

[maxwedge]

GMMerlin, don't tell me do did that from rote, please??!@! Great info and GM, probably as you know, ignition switches have been problematic on the Envoy/Trailblazer models.

[GMMerlin]

Originally Posted by maxwedge

GMMerlin, don't tell me do did that from rote, please??!@! Great info and GM, probably as you know, ignition switches have been problematic on the Envoy/Trailblazer models.

Yes this is true, but I am a firm believer in trying to diagnose a concern before I throw a part at it.
Sometimes people get in one mindset and start replacing parts before they confirm the problem.

[mvftw]

Do these have a crank sensor on them?

[GMMerlin]

Originally Posted by mvftw

Do these have a crank sensor on them?

Yes they do, but they have not been an issue on these engines.
The CKP signal is not needed for the engine to start and run on this system, it can use the CMP signal to determine ignition strategy