2008 Trailblazer dies randomly

[shepherd92683]

For a few months I've been dealing with this issue. I had the codes read and it said I had a bad ignition coil #3, so I replaced it. I was good for 10-14 days, then the problem came back. Speed isn't a factor when it happens, but the REP, check engine, and traction control lights all come on and the vehicle dies. After a few minutes typically, sometimes quicker, it will fire back up and only the check engine light will stay on and even turn off at times. I did a check myself on all of the coils by pulling them out slightly to see if the motor sputtered or remains running (which removing each one the motor sputtered) because it was the same type of issue that happened before I changed the coil. I have about 70k on my plugs, and just thoroughly cleaned the throttle body. I tried going to O'Reillys to scan the check engine light but of course my cigarette lighter plug is either unplugged or the fuse is blown so they couldn't read it. Any ideas aside from getting the light checked what this could be that I can check myself? Thanks

 

[Blckshdw]

Try swapping the spark plug in #3 with another one, see if the code moves with it, or stays in place.

 

[Mounce]

Step one for me would be replacing the fuse so that you can tell us which codes are popping up now. Without the codes it's kind of a guessing game.

 

[shepherd92683]

So I had the light checked... AutoZone said ECM failure. O'Reilly's says PCM failure (P0601) and MAF sensor is bad.

I removed my PCM fuse (only have one, I've read there is 2?) and removed the MAF sensor and made sure connections were clean and reinstalled it. Nothing has changed. I guess the only other thing i have noticed is that it only happens on drives over 20-30 mins and it has happened a few times while slowing down.

The check engine light went off after what I did, then came back on the next morning. After work, it was off again. I'd really like to avoid the dealership but I'm running out of ideas.

 

[BlazingTrails]

there is nothing wrong with your PCM, replace the lighter fuse in the under hood fuse panel IIRC it is #15 but check them all.

The main problem you are having is most likely going to be the ignition switch.

 

[Wooluf1952]

The fuse for the OBDII is #13 under the hood.

 

[shepherd92683]

Dealer just told me it is a failed ECM. $550 to fix. Any thoughts to cut the cost of this?

 

[Mooseman]

Try finding a used one, do the security relearn yourself and have the dealer just do the CASE relearn. That should cost less than a new one and save some labour.

 

[Blckshdw]

Try finding a used one, do the security relearn yourself and have the dealer just do the CASE relearn. That should cost less than a new one and save some labour.

or buy a tuned one from Limeswap or PCMofNC. Still cheaper than that

 

[shepherd92683]

or buy a tuned one from Limeswap or PCMofNC. Still cheaper than that

Thanks! I am a rookie on the PCM/ECM business... I am looking on eBay for the correct part. I know that it must be programmed regardless. Anything I should look for or stay away from?

 

[Blckshdw]

Buy the module directly from either of those companies, they can put the tune on it for you, then you just have to get the CASE relearn done. Go to their websites, poke around and look at your options. That will help make things more clear.

 

[shepherd92683]

Could the bad ecm mean a fuel reduction of 3-4 mpg? Because my mileage has been crap since this happened it seems.

 

[Blckshdw]

ECM= Engine Control Module, so yeah, if that isn't telling the engine's components to do the right things at the right times, your MPGs will suffer, as well as some other things potentially.

 

[Mooseman]

If you have a pick-a-part close by, find one there or a local yard. Would probably be cheaper than eBay. Or like Blkshdw said, check with PCMofNC or Lime-Swap (Member @limequat ) to buy an tuned PCM outright. It will be tuned for some performance enhancements but it will still need for you to do a security relearn and then, once it's running, get the CASE (Crankshaft Angle Sensor error) relearn at the dealer done. It will run without it. It's just for an error code. If you just want a regular used PCM, find one with the same gearing as yours to avoid having to get it reprogrammed. This aspect may be easier by getting one that's tuned rather than a used one.

The security relearn is:
1. Turn the key to ignition on and then try to start it. It will not start. Leave it with the ignition on
2. When the security light goes out (~ 10 minutes), turn the key to off for about 5 seconds. Repeat procedure 2 more times.
3. On the third time, it should start.

Personally, I like Lime-Swap. Better prices and great service.

 

[shepherd92683]

I just put my limeswap in and it started right up...also turned on my oil change light. I'm 2500 miles away from my next oil change so that's odd unless that just resets when the ECM is replaced. Also odd that I didn't have to do the security relearn.
I won't be able to get the case relearn done for a few days and will do a few hundred miles of driving in the mean time. Are there any known issues of doing this? Thanks

 

[Mooseman]

None. It's just to tell you if the camshaft angle is not jiving with the crankshaft. It willl also inhibit the cruise control. For the OLM, maybe the replacement PCM was due for an oil change when it was pulled from the donor.

 

[Wooluf1952]

For the OLM, maybe the replacement PCM was due for an oil change when it was pulled from the donor.

^ This. The info for the OLM is stored in the PCM. So changing the PCM will give you the reading for the vehicle it was removed from. Remember the mileage and/or the percentage left and go by that for your next oil change.

 

[shepherd92683]

None. It's just to tell you if the camshaft angle is not jiving with the crankshaft. It willl also inhibit the cruise control. For the OLM, maybe the replacement PCM was due for an oil change when it was pulled from the donor.

This will make for a long 3 hour drive!

 

[shepherd92683]

I just went to leave for the first time today and I couldn't go over 15-20 mph. I drove around the block twice, sat at a stop sign for about 10 seconds and it went back to normal. Is that normal until I do the case relearn?

 

[Wooluf1952]

I just went to leave for the first time today and I couldn't go over 15-20 mph. I drove around the block twice, sat at a stop sign for about 10 seconds and it went back to normal. Is that normal until I do the case relearn?

Did you get a CEL?

 

[shepherd92683]

It has been on since before I replaced the pcm.

 

[Mooseman]

Codes?

 

[mrrsm]

FWIW...This 2006 TB that the Service Technician is working on in this video and the comments provided seem relevant and the SUV problem bears most of the earmarks you have described.... including a recommendation in the comments section to replace the PCM as per the above member suggestions. In order to see aditional comments not seen here... please visit Youtube and search for this video under the title of: "2006 Trailblazer Testing" and then expand all comments for the full details... Watching It is going to be about as exiting was watching paint dry.... but the conclusion involving the thermodynamics of the problem might make it worth viewing:

 

[shepherd92683]

Codes?

The code was that the ECM was bad. Dealer didn't tell me what the P code was, he did it free and just reported out the problem. I can always take it elsewhere to see what it says.

 

[shepherd92683]

FWIW...This 2006 TB that the Service Technician is working on in this video and the comments provided seem relevant and the SUV problem bears most of the earmarks you have described.... including a recommendation in the comments section to replace the PCM as per the above member suggestions. In order to see aditional comments not seen here... please visit Youtube and search for this video under the title of: "2006 Trailblazer Testing" and then expand all comments for the full details... Watching It is going to about as exiting was watching paint dry.... but the conclusion involving the thermal dynamics of the problem might make it worth viewing:

So I need to carry a heat gun to warm up my ECM when my car dies? Lol... That's all I gathered from the video.

 

[mrrsm]

"Dealer just told me it is a failed ECM."

More than likely... adding heat into the PCM allows either a loose, non-solid state component to make electrical contact or there is a spot somewhere on its internal Bread Board...that makes it function only when the contact succeeds. If you check the detailed comments on Youtube... you will see that before they did this test, the Technician removed the PCM from the vehicle and placed it in a freezer for a while to establish the circumstances of it not cranking when it was literally Ice Cold. In any case... Getting another opinion contrary to the original Dealership diagnosis will probably just confirm the original one.

 

[shepherd92683]

I have no doubt the pcm was bad. I've replaced it either way so that's irrelevant at this point. The question is why did my TB only drive 15-20 mph, then after running idle decide to drive normal again? Has anyone had that happen to them before?

 

[gmcman]

Before your symptoms started, did you perform any work to your TB? Did you remove or replace anything? Plugs?

I would look for a loose ground, start with the battery connections, as well as the PCM harness however I'm not sure which wire is the ground for the PCM.

So this is your 2nd PCM and it's doing the same thing? If so I doubt it's the PCM but could have gone bad again. Check your connections, and alternator voltage output with a multi meter, not the dash gauge.

 

[mrrsm]

"The question is why did my TB only drive 15-20 mph, then after running idle decide to drive normal again?"

You mentioned the plugs being in the motor for 70,000 miles... but what is the total mileage on the vehicle now? When you were running the TB with the original PCM "for a few months" and had the Bad Coil issue.... was the engine running especially rich? If so... over those few months, perhaps the Catalytic Converter was getting clogged... and then only started improving after you put the second PCM in and the F/A ratios came back in line. The new PCM behavior might have given the CAT a chance to heat up properly and burn away SOME of the excess internal unburned fuel by-product residue.

You can test if the CAT is bad by cheating a little and relieve any excess back pressure by temporarily removing the Oxygen Sensor in the Upstream location, effectively bleeding off excess back-pressure at that point while you drive a short distance and see if your engine develops more power. If the result is that it does get better... then "The CAT is The Culprit".

One other impediment that can add to a loss of engine power is a very clogged fuel filter.

 

[gmcman]

Blazing Trailz gave a good recommendation. ...have you tried it?

Your code stating that the ECM is bad does not neccesarily point to the ECM....that's not how codes are supposed to be read, something else is causing that light to come on.

Just like an upstream O2 sensor is lean, it's not generally the sensor, it's an incorrect fuel mixture causing the sensor to read outside it's set parameters.

It's cheap insurance to replace the ignition switch, they are a known high failure item.

 

[shepherd92683]

So heres what I've found thus far...

My vehicle only seems to do the "shuffle" of 15-20 mph when I first start to drive.... It happens when I start, reverse(without making a delayed stop) and start driving again. If I stop again later for a moment or two...hard to explain but its like the speed limiter of reverse cuts off of drive and it converts to the drivetrain to let it drive regular again.

I was very timid of doing a tune... I am trustworthy of it due to the extreme experience that is referring me in this instance. I am quite unsure of the tune at this point because I was supposed to get 1-2 mpg gain but I am at a -2....

I used to get an AVERAGE of 17 but now I'm at 15.8, and thats with 2 trips of solid highway driving at 75 mph....What gives, at one point I got an average of 20 mpg... What do I need to do to be back at that number?

I want to make my TB what it should be... I have about 3-400 lbs of BANG in the back so I do understand that the extra weight is a sacrifice...but 15.... NO...

I have changed the upstream o2, alt, water pump(doesn't affect mpg) new Mechman alt, and so many other things it silly. WTF else can I do?

 

[mrrsm]

Okay... as crazy as this is going to sound...take a piece of Laser Printer paper and cut it in half lengthwise. Then start your vehicle and let it idle until it warms up. Set the Parking Brake and walk to the back of the TB and lay the one sheet of paper flat and level over the very tail end of the Exhaust Pipe... if the engine valve train is functioning nominally...that paper should flutter and vibrate against the outer ring of the Exhaust Pipe....

But.....

If the paper gets SUCKED ALL THE WAY UP INSIDE THE PIPE... then this is a definitive Test for Burned Exhaust Valves... and would explain the extreme loss of power and also the sudden loss of good gas mileage because the fuel and air being drawn inside the involved cylinder(s) is not being compressed enough to burn properly and give power as a result. The spark plug(s) will show black unburned fuel from the fuel collecting and fouling the plug. The engine cannot make power without compression in ALL cylinders. The O2 Sensors Go Crazy and the CAT is is in danger of clogging up and being ruined.

The reason the paper gets pulled up inside the exhaust pipe is because when the valves are warped...and the piston is moving downward in the cylinder on the Intake Stroke... the partial vacuum it causes will PULL the exhaust back inside the cylinder ...hence drawing the in the paper like sucking soda up inside a soda straw.

The only other thing that can come close to this phenomena happens when somebody changes the Spark Plugs and places the COP (Coil On Plug) Ignition Wire Connectors on the WRONG COPs.... the engine staggers after that because the Wrong Spark Plugs are being fired at The Right Time... but at the Wrong Position in the Four Stroke Cycle... Bye Bye Engine if this is not soon corrected because having the ignition sequence firing out of order will pound the Crankshaft Bearings to smithereens if two cylinders fire off simultaneously or in very close timing during the power stroke.

 

[gmcman]

I don't want to say this is 100% true, but a normally running engine will constantly blow the paper away from the tailpipe unless you have a very radical cam.

If it gets sucked back against the opening then you may have a sticking exhaust valve. These engines have a very short overlap and shouldn't have any reverse flow noticeable at the exhaust tip.

Now......Shepherd....this is where we need some info. Not to sound upset, but when people ask for help, and we ask questions and don't get a response, it's hard to try to figure things out.

Have you checked your alternator output voltage with a meter?

Before you changed your PCM, did you do any other work to the vehicle?

What plugs did you install? Should be only AC 41-103.

If you damaged something in the alternator, you could be outputting more voltage then what's safe and frying components.

These platforms aren't known for damaging subsequent PCM's.