Stability control leads to stalling

Chad Technician Winter park, Florida Posted   Latest   Edited  
Question
Driveability
2008 Chevrolet Trailblazer 4.2L (S) 4-spd (4L60-E)
C0455 - ISO/SAE Reserved
C0196 - ISO/SAE Reserved
Cuts Out

This began with an intermittent stability light. The light was not in when I got the vehicle. I pull codes. C0455, C0196 History codes not current. 

My scanner states a t.s.b for software update in regards to C0455. But I am unable to verify current software. 

Go on test drive, live data looks good. I don’t see anything that raises and eyebrow. I keep my eyes on steering angle degree, steering angle voltage, phase a and phase b. 

Upon returning after 5 miles or so, vehicle stalls as I’m pulling back into the Service bay. Unfortunately my scanner looses communication when key is cycled Or this stall happens. So I can see graphed data. It stalls a couple more times just sitting at idle. I notice it’s when the steering wheel is moved. 

I do a full system scan again. No additional fault codes found. Customer admits vehicle has stalled before. They had a new cam sensor and phaser so I scoped it. looked great. Vehicle would not stall again. 

Now sorry to waste everyone’s time. But I need advice on these waveforms. I decided to look at the can bus for fun just because I never get to do this. It goes 0-7volts good I think. But from the known good in my ATG book this doesn’t look right. Any thoughts???? 

I zoomed out for each of the pictures. Same waveform

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diag​.​net/file/f2dhbxy1w…

diag​.​net/file/f16ea2wk2…

0
Tim Curriculum Developer
San Diego, California
Tim
 

Hi Chad. This vehicle has Class 2 as well as CAN, and your captures look like Class 2. Also, I think the time base may be too long, which makes the waveform look erratic when zoomed in. In other words, these waveforms may be completely normal. Let me know if this doesn't help. Thanks,

+5 Ð Bounty Awarded
Chad Technician
Winter park, Florida
Chad
 

Thanks Tim. I figured I was off on something. This is a capture of class 2. Practice practice

0 Ð Bounty Awarded
Matt Diagnostician
Red Wing, Minnesota
Matt
 

Agreed. If I'm seeing the time-base correctly, the sweep is 1S/screen. Snap On, iirc, collects 262 screens (at that sweep) which would be a 262 second capture of Class 2 data. That's a ton of time and therefore the scope is aliasing. The way the Snap-On scope capture data it is imperative to set the sweep fast enough, often fast enough that the live screen is "zoomed in" enough for detail. The

+3 Ð Bounty Awarded
Chad Technician
Winter park, Florida
Chad
 

Thanks Matt. I think I’ll be looking at this vehicle Tuesday. I’m gonna grab another capture. Even tho it’s good I thinknit will help me learn some

+1 Ð Bounty Awarded
Martin Diagnostician
Burleson, Texas
Martin
 

Is the throttle nice and clean? Maybe the extra load while turning is causing the stall.

+3 Ð Bounty Awarded
Chad Technician
Winter park, Florida
Chad
 

hey Martin, I was hoping to get it to stalk more. It wouldn’t. I dont like to do little things before finding my fault. It did come across my mind. I was looking for a power steering pressure switch. Didn’t find one nor did I find a description on how that system works. Idle speed would change when wheel was moved. Ill see the vehicle aganext week. I’ll test drive it , give it another go. Also

+1 Ð Bounty Awarded
Adrean Diagnostician
Bakersfield, California
Adrean
 

I would agree with Tim on that capture . When stalling does it start back up right away?

0 Ð Bounty Awarded
Chad Technician
Winter park, Florida
Chad
 

Hi Adrian. A coworker has same vehicle. I’ll be able to do a comparison on Saturday. I’ll check it from different time bases. It seemed the key would need to be cycled. Otherwise it would crank no start. Once cycled it started.

+1 Ð Bounty Awarded