2008 tahoe hybrid strange noise at highway speeds
 

purchased a 2008 Tahoe Hybrid a few months ago. Great vehicle love it on way home from recent trip at approx.... 75 mph a thumping noise started from the front end almost like a flat spot in the tire. BUT it is intermittent ... stops and stars randomly. goes for hundred miles with no return then there it is again
Does anyone have any idea what this could be ??????
only code on car is PO61B when plugged in to code reader

Thanks for any help

Newbie to this forum and appreciate your help
I have read and read but no similiar issues come up

Thanks Norm

Re: 2008 tahoe hybrid strange noise at highway speeds
 

Get everything that rotates in front end looked at. Tires, wheels, wheel bearings, front 4X4 propshafts if so equipped.

NONE of that will ever set a code. None of that is hybrid unique.

Sorry, sometimes wheel bearings that are starting to go will set ABS sensor codes.

Re: 2008 tahoe hybrid strange noise at highway speeds
 

If it was a wheel bearing issue it would be constant and not go away. I checked all the front end and nothing is obvious . Thinking there maybe a control module or something that is failing and causing intermittent thumping in front end. going to put it on a maching and try and figure this out
Thanks for the reply

Re: 2008 tahoe hybrid strange noise at highway speeds
 

I have personal experience with these trucks and wheel bearings. Yes the noise will come and go on these types of bearings. Usually a buzz or growl.

If you find a module doing it. Let us know..

I had 195k with stock 22" wheels in my escalade hybrid. Bearings should last that long.

Re: 2008 tahoe hybrid strange noise at highway speeds
 

We have 145 K on our Tahoe Hybrid , I will be pulling the bearings on Monday , Just never had bearings be intermittent and only at speeds above 65
Tried to get it on my buddys machine yesterday with no availability . I hope to get this figured out next week. My wife has had it stall on her also 2 times over the last few months. I am reading up on that issue as well.
Thanks for the help

Re: 2008 tahoe hybrid strange noise at highway speeds
 

Known issue with all of them not just hybrids. When they are bad you can manually wiggle the wheel with the weight of the truck off it and the wheel in the air.

Seen them as soon as 65k and nothing out past 250k.

If they do NOT move in directions that they should NOT, save your money and look elsewhere.

Stalling? P061B? You need to get a dealer type scan tool that can get Freeze Frames. Any time a code sets, the computer takes a "black box like" pre-determined list of data points about the time of the code.

NOLE: The Engine, Hybrid, and Transmission computers ALL take these Freeze Frames. You have to dig deeper most of the time.

P0AC4 means Hybrid told engine to turn on the Check Engine Light P0700 means that the transmission told the engine to turn on the light. So depending on who told the engine to turn on the light... look there for more information and the casue Freeze Frames

The computers that run the HV battery and the traction drive motors forward their "issues" to the hybrid computer. The right scan tool can interrogate them too.

From Freeze Frame data you can narrow down what the vehicle was doing, Mode or Gear. How fast, engine temperatures, hybrid motor parameters, HV battery parameters.

These Freeze Frames are the best way to begin the real diagnostic path, not just an Easter Egg hunt.

Re: 2008 tahoe hybrid strange noise at highway speeds
 

Thanks Hillbilly for the information, I have a friend who has a machine in his automotive shop that can read all the codes and will be going there monday to try and figure it out

Re: 2008 tahoe hybrid strange noise at highway speeds
 

Well put it on the tech2 friday and pulled the codes and freeze frames. Ran the diagnostics as the tech bulletins requested. All checked out as good to go. Reset codes and all good through the weekend so far. Oil pressure sending unit had an intermittent failure code so going to change that out tomorrow, just to eliminate it from the equation. Hate not finding a smoking gun

Re: 2008 tahoe hybrid strange noise at highway speeds
 

Thanks for the update. The data always helps but old-school moving parts don't always show up.