Flashing check engine light.

[coolride]

I went for a drive yesterday and at startup I noticed that it was idling low (about 500rpm) and a couple miles from the house, the CEL started to flash. I pulled over and let it idle while I also google searched "flashing CEL." I understand that it's an unspecific miss condition.

So the engine is missing but the computer doesn't know where? While I sat there looking at my phone the flashing light went away. The TB ran perfectly fine except for the low idle at startup. Any ideas about what's going on?

 

[Blckshdw]

Usually when we get a misfire, it takes the PCM a couple of drive cycles to zero in on which cylinder is the culprit. You would get a P0300 code, until it settled on a P030# (where the # corresponds to which cylinder)

So when the light was flashing, was the engine missing, or was it still running/idling fine?

 

[coolride]

When the light started to flash, the engine was running fine.

 

[coolride]

Nice cool morning here (50 in the shade) and I went for a short drive. It idled fine at start up (1100rpm,) then it dropped to 1000rpm and then to 900rpm. After the engine warmed up it idled at 600rpm. No CELs and it ran very nice.

These dash lights came on though.

 

[TequilaWarrior]

Traction control. The wrench indicates an issue with traction control - most likely an ABS sensor. The triangle light may indicate either that it's attempting to engage or that you've turned it off (stabilitrak). Check to make sure you haven't pressed the stabilitrak off button on your gearshift. Do you have any bearing noise coming from the front? You may want to jack the front up and check for wheel play (pulling/pushing each tire top & bottom alternately and feeling for play with the car jacked up). Side to side play is usually indicative of a ball joint issue whereas top&bottom play is indicative of wheel bearing wear / failure (or just a good time, depending on how much innuendo you want to read into it).

As for your misfires and flashing CEL. I'd pull codes and see what's set. If you don't have a scanner or Torque app, you can usually get it done at most auto parts stores for free.
Also, if you're up to it, clean your throttle body as that can cause rough idling - reset your PCM by pulling the PCM fuses while cleaning the throttle body.
I'm also not afraid to pull the plugs and look at them from time to time although some people would discourage such activity as they feel repeated removal and reinstallation of the same plugs over and over can lead to seizing. I've not experienced this, however. I'll also clean the plug while I have it out - by spraying it down with an aggressive cleaner like carb&choke cleaner. NEVER use a brush on "Iridium" spark plugs (factory plugs) and only ever replace the plugs in a Trailblazer with ACDelco 41-103 plugs (at about $7ish apiece as they are Iridium, watch out for counterfeits).

 

[coolride]

The previous owner just paid a small fortune to have all 4 bearings (and hubs) replaced. I just checked my FIXD bluetooth scanner and there are no codes. The throttle body is super clean (I recently pulled it and did the work) and the plugs and coils were also inspected, and cleaned (they didn't look great.) The plugs were not changed (except #6, with a 41-103.) I'll check for a Stabilitrack button on the gear shifter, never realized that the shifter had buttons.

 

[TequilaWarrior]

The previous owner just paid a small fortune to have all 4 bearings (and hubs) replaced. I just checked my FIXD bluetooth scanner and there are no codes. The throttle body is super clean (I recently pulled it and did the work) and the plugs and coils were also inspected, and cleaned (they didn't look great.) The plugs were not changed (except #6, with a 41-103.) I'll check for a Stabilitrack button on the gear shifter, never realized that the shifter had buttons.

I'm not sure what year they started putting stabilitrak (with the off button on the gear shift) in these vehicles.


My Bravada occasionally has periods of shi.... er... rough idle. I've not found any good reason other than sometimes it's the A/C compressor kicking on.

As for the wheel bearings... the bearings could be in 100% good shape and the ABS sensors sending poor signal. If rust builds up on the surface of the wheel bearing flange where the sensor mounts, it will send crappy signal. The fix is to remove the sensor, clean the mounting area (keeping rust out of the mounting hole), applying a very light coat of paint, and remounting the sensor. Of course this is assuming that it's the ABS sensor that's causing the issue.

 

[coolride]

Just had a look, and yeah. Didn't notice that button there. (What's it for?)

 

[TJBaker57]

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[TequilaWarrior]

Just had a look, and yeah. Didn't notice that button there. (What's it for?)

If I recall correctly, pressing the button turns off traction control and holding it in for 10 seconds disables stabilitrak.
Traction control keeps you moving in a limited traction situation (mud, snow). Stabilitrak keeps you from rolling the vehicle when you're driving like an idiot (or in slippery conditions). It also makes the car behave in a more stable way - the description @TJBaker57 posted is perfect.

Thinking about it, if those lights keep coming on you might have a pinched / broken wire to that button. You may need to pull the shifter boot and check the wires to the switch and the switch itself.

 

[coolasice]

Is anything plugged into your obd port? I had same problems and turned out to be a faulty Bluetooth obd scanner screwing with my data signals.

 

[coolride]

No, the port was clear.

 

[Mooseman]

If only the Stabilitrak/traction control lights are on, it's likely the steering wheel position sensor. If the ABS light is on along with the others, then it's more likely a wheel sensor.

 

[TequilaWarrior]

If only the Stabilitrak/traction control lights are on, it's likely the steering wheel position sensor. If the ABS light is on along with the others, then it's more likely a wheel sensor.

I forgot about the SWP sensor... good call @Mooseman .

 

[mrrsm]

If you are getting a sketchy signal from either (or both) front wheel ABS sensors... This video shows the best way to clean them up along with providing a Good Explanation as to WHY the ABS Sensor(s) goes sideways:

Also... If you still have a Flashing CEL afterwards AND have any P03XX Codes remaining persistent on your Scanner... Your immediate concern should be to address this Misfire Problem as soon as possible. At 2:42 into this next video, the Instructor (Teaching Universal aspects of Diagnosing P03XX Codes using Tech 2 and Other High End Scanners) points out the Two Types of Misfires that are involved.

The serious nature of having HIGH repeat Misfire Counts... is that So MUCH Fuel is being dumped into the CAT where it gets burned in concentrations that can increase your Noxious Exhaust levels as much as 1.5 Xs the Normal amount.

So, instead of contributing to the Engine Power... the GASOLINE PASSING THROUGH can raise the CAT Temperatures significantly high enough ...to destroy it. You will see this "Incandescently Hot CAT" Glow Phenomena in action inside of a Doomed Converter within the first minute of watching this video:

 

[Kelly@PCMofNC]

You might want to find a better scan tool to use (i.e. one that can read the EBCM/etc), that can tell you what the pending codes are relating to traction control/ABS/etc.

 

[coolride]

That FIXD scanner is a complete waste of money. Please do not buy one. It was a gift from my GF and she had no idea that it was a complete rip off.

 

[mrrsm]

If you decide to delve into analyzing EFI and Engine Component Bad Wave Forms versus Expected Wave Forms to improve your Diagnostic Testing possibilities, Amazon has a nice listing of what can be had in the way of Automotive Oscilloscopes... depending upon what your 'Wallet' can stand:

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Naturally, these sensitive devices vary in Quality, Performance and Price and this Video will demonstrate how they generally work and what to look for in features involving:

Measuring Voltage over Time:

...and for a look at another example of an inexpensive Oscilloscope, the Hantek Oscilloscope being offered on Amazon as described briefly in this other Video:

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Amazon also carries an inexpensive Hantek Low Amp Clamp Probe that will complement the suggested Hantek USB Powered Oscilloscope:

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For a more discreet, smaller wire Amp Clamp... this version will be more appropriate:

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[Blckshdw]

That FIXD scanner is a complete waste of money. Please do not buy one. It was a gift from my GF and she had no idea that it was a complete rip off.

What went wrong with it? I've been using the cheap $10 blue mini adapters, with pretty good longevity.

 

[TJBaker57]

Didn't notice that button there. (What's it for?)

You can download your owners manual here (assuming you don't have the original) and it explains quite thoroughly the Stabilitrak System.

https://my.chevrolet.com/content/dam/gmownercenter/gmna/dynamic/manuals/2006/chevrolet/trailblazer/2006_chevrolet_trailblazer_owners.pdf

I'm not sure what year they started putting stabilitrak (with the off button on the gear shift) in these vehicles.

I just compared the 2005 and 2006 owners manuals and it seems 2006 was the first year for Stabilitrak in the Trailblazer.

 

[TJBaker57]

the cheap $10 blue mini adapters, with pretty good longevity.

Agreed, I have 3 of them scattered about and all are at least 6 years old. And if you are willing to learn how to use them you can accomplish quite a lot.

 

[coolride]

What went wrong with it? I've been using the cheap $10 blue mini adapters, with pretty good longevity.

To use the scanner (I had it sitting around for a year) you have to register with google and give up all kinds of personal information. It might be easier with an Apple device. And after all that trouble and expense, it just simply reads the check engine light code. Unless you want to pay more, then they will gladly take more of your money. Half of the scanner's programing is designed to up-sell the user extra features.

 

[coolride]

Traction control. The wrench indicates an issue with traction control - most likely an ABS sensor. The triangle light may indicate either that it's attempting to engage or that you've turned it off (stabilitrak). Check to make sure you haven't pressed the stabilitrak off button on your gearshift. Do you have any bearing noise coming from the front? You may want to jack the front up and check for wheel play (pulling/pushing each tire top & bottom alternately and feeling for play with the car jacked up). Side to side play is usually indicative of a ball joint issue whereas top&bottom play is indicative of wheel bearing wear / failure (or just a good time, depending on how much innuendo you want to read into it).

As for your misfires and flashing CEL. I'd pull codes and see what's set. If you don't have a scanner or Torque app, you can usually get it done at most auto parts stores for free.
Also, if you're up to it, clean your throttle body as that can cause rough idling - reset your PCM by pulling the PCM fuses while cleaning the throttle body.
I'm also not afraid to pull the plugs and look at them from time to time although some people would discourage such activity as they feel repeated removal and reinstallation of the same plugs over and over can lead to seizing. I've not experienced this, however. I'll also clean the plug while I have it out - by spraying it down with an aggressive cleaner like carb&choke cleaner. NEVER use a brush on "Iridium" spark plugs (factory plugs) and only ever replace the plugs in a Trailblazer with ACDelco 41-103 plugs (at about $7ish apiece as they are Iridium, watch out for counterfeits).

Yesterday I grabbed the top of the front wheel and rocked it back and forth. Turns out that the upper ball joint is shot. It had lots of play. Something is loose on the passenger side too.

 

[TequilaWarrior]

Yesterday I grabbed the top of the front wheel and rocked it back and forth. Turns out that the upper ball joint is shot. It had lots of play. Something is loose on the passenger side too.

I just reread what I posted... oof. Up / Down play is indicative of Ball Joint or bearing play. Side To Side play is indicative of tie rod or bearing play. If the up down play and the side to side play are the same, I lean towards bearing. UNLESS, of course, you actually see a problem with the ball joint or tie rod end. Ball joint / tie rod issues should not cause any traction control / abs / stabilitrak issues. There is a way to check for "tone" from the abs sensors without a code reader, but I've never personally done it. From what I remember you need to spin the wheel at a constant rate (like 60 RPM or something) and measure the voltage coming from the abs sensor. It's in millivolts - another reason I haven't done it, nothing I have is ~that~ sensitive.

 

[coolride]

I can clearly see the upper ball joint moving around.

 

[coolride]

Just put a couple Moog K6664 ball joints on order through Amazon. If anyone has a suggestion about anything else that should be replaced (as long as I'm in there replacing upper ball joints,) I'd appreciate it.

 

[Mooseman]

This thread has gone way off topic. Started with a misfire and now talking about ball joints. Please start another thread if needed.