Lean on both banks, Stabiltrak and Traction control and Jitter brakes on some cold starts

Tiny
FOREMORE
  • MEMBER
  • 2007 CHEVROLET SILVERADO
  • 4.8L
  • V8
  • 4WD
  • AUTOMATIC
  • 168,000 MILES
When engine light goes on the traction control and stabilitrak light goes on and says it needs maintenance. Engine codes are always PP0171 and P0174 lean on both banks. The engine light goes off after a couple on and offs (7ish) and sometimes goes off around 4ish. Traction control / Stabilitrak always go off after a gear change. I get poor performance when engine light is on (Limp mode?) Every once in a while I get the traction control and stabilitrak lights when I am idleing or low RPM in first gear. When gears automatically change from idle / 1rst to 2nd gear I feel and hear a large "clunk" as it shifts and I get a horrible jolt. I can always minimize this with not accelerating right before the gear change when I know about it. The traction /stabilitrak light always turn off after a gear change. I can almost always get the Traction control and Stabilitrak lights to flash if I tap the brakes a lot or ride the brakes and let go then ride the brakes some more. The Stabilitrak and the Traction control are never separate and both come on always together. Only sometimes does the check engine light for both lean codes come on after these lights. The check engine (lean codes) never comes on without first the Stabilitrak / traction control lights come on, and then the Stabilitrak / traction control lights disappear after a gear change. Whenever I first start my truck and am backing out of the drive way (a little bit of a grade) or driving down the first couple streets in the neighborhood my brakes click (ABS), like I am skidding but I am not. The brakes function normally after 30 secs or so of the truck being on.


I can go weeks with out any symptoms then seemingly random or when I am ridding my brakes or in stop and go traffic I get the symptoms again.

I feel like these are related in some way:
1. I get lean codes engine light only after traction control light and stabilitrak
2. The brakes more often then not jitter only when check engine is on
3. Traction control and stabilitrak lights with a large jolt after can make the check engine light go on also.

what I would think this is:
1. Brake booster vacuum leak
2. PCV system, hose leak or PCV valve, or PCV gasket, or the connections for the hose
3. EGR valve or gasket
4. MAF (have cleaned this once with no change)
5. Fuel system either it be pressure or it be fuel injectors
6. O2 sensor is my last bet.

do you have any ideas for me?

Thanks.
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Friday, October 31st, 2014 AT 9:56 AM

4 Replies

Tiny
SATURNTECH9
  • EXPERT
I have never seen a lean code set off a traction control or abs light off before. Your going to have to have a professional scan done to get the brake system codes. As far as the lean codes the first thing I would suspect is a vacuum leak. The best way to pin point a vacuum leak is with a smoke test. The charge around 100 plus to get one done at a shop. The automotive smoke machines are pretty expensive I made my own machine out of spare parts laying around works pretty good. As far as saying what it is cant say right now but a smoke test is where I would start.
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Friday, October 31st, 2014 AT 12:23 PM
Tiny
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SO I have been researching this for quite some time (about a year). Since it hasn't really effected driving and doesn't mess with saftey's and emissions (just passed this month) I wasn't to worried about letting it go and trying to figure it out on my own.

I believe I have found the problem. Don't know how to fix it or what to fix. The issue only happens when I am riding my brakes or stopped but here is the kicker: when I am doing this WITH THE BRAKE PEDAL SLIGHTLY PRESSED. Sorry to CAP's that but that was an important part. All these issues, the satbilitrak and traction control, the engine light, the brakes jittering like I am skidding but not, the misfire after first gear change, all root from me not pressing in the brake pedal to the full extent. I rarely hard press brake pedals in any car, even when I am stopped. Just habit I guess. So now saying this.I think it comes down to the truck's computer isn't getting the signal I am pressing the brakes when I do softly. I CAN DUPLICATE THIS EVERY TIME. I either get a misfire, the stabilitrak/traction control lights or the engine light every time I ride my brakes softly or am in idle with the brakes softly pressed. Just barely to keep the truck stopped while in automatic gear. Come to think of it I remember now that my brake lights don't always turn on unless I firmly press the brakes.

What mechanisms are there that senses the brake pedals? I know of the brake pedal sensor. I have changed that sensor about 6 months ago and still had issues so left it with new. The lights had the same issue not turning on while slightly pressing with new and old sensor. Should I look into brake pedal position sensor calibration (such a thing in a Silverado)? Is there something to look at in the brake system other then this sensor? Does that sensor tell the computer the brakes are pressed and how hard they are pressed or is there another?
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Thursday, November 6th, 2014 AT 7:46 AM
Tiny
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  • MEMBER
This was insightful:

1. A new BPPS must be zeroed out using a tech 2
1a. the BPPS and the BCM need to be synched
1b. the BCM needs cleaning with deoxit D series and protector gold series if corroded
2. Issue may be in the BPPS harness (wire connections)
3. Tech II told him the faults and what to do (front right hub costs $115)

http://www.techconnectcanada.com/techtips_2012monthly.php
Use a scan tool to check that the Brake Pedal Position Sensor (BPPS) ratio is equal to the BPPS learned home when the brake pedal is not depressed. If they are equal, the brake lamps should be operating correctly. If they are not equal, perform the Brake Pedal Position Sensor Calibration procedure in the appropriate Service Information to complete the repair.

so what I get from this is I need to do a tech II reading, get the codes from the stabilitrak and traction control lights, see if the hubs need replacing on the front or if the BPPS and BCM are equal..if so (or not) reset to calibrate. Also I need to clean the BCM connections and use some anti corrod stuff inside. I also need to check the BPPS for faults in the cableing

does that all sound correct?
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Thursday, November 6th, 2014 AT 9:19 AM
Tiny
SATURNTECH9
  • EXPERT
I posted how the abs etc operates I don't see a pedal position sensor on that system you can read the parts in the system in the info I posted. As far as the brake sensing there is a brake switch on the brake pedal. The best thing to do is to read the codes on the abs/traction control computers. Thats the first thing I would do if I had it in front of me the codes would give us a trouble tree and direction to go. Plus we could research the codes maybe your brake booster is leaking vacuum when you step on the brakes.I have seen that happen before. We really need those code numbers to help figure out the problem. Also how far does the brake pedal have to move before the brake lights come on?ALso there is a brake pressure sensor that shows how much pressure is coming from the master cylinder. Will all those lights come on and the traction control kick in under normal braking and not just lightly applying the brakes?Also cant tell if one of the speed sensors might be bad since we don't have the codes to see if were leading towards that direction.
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Thursday, November 6th, 2014 AT 6:58 PM

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