2009 Tahoe bump / shudder / jerk, P0AC4 P0BBD + low oil pressure fixes

  #1  
Old 03-31-2019, 09:37 PM
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Default 2009 Tahoe bump / shudder / jerk, P0AC4 P0BBD + low oil pressure fixes

Hey folks - like most of us my Tahoe, currently at 95k miles has been having transmission-like bumping and jerking around. In the morning it was sluggish to take off, and occasionally would slip into neutral in reverse. When i'm below 30 miles per hour, I have myriad issues, the scariest being a sort of transmission clutch slip / shudder when going very slowly. Every once in awhile I pull codes P0AC4 and P0BBD - the last time I had them, they popped up, and went away within 5 minutes... weird.

Secondly, my oil pressure when driving on highway hovers around 30-35. When idling it's just above 20. Every once in awhile it pulls a CEL for low oil pressure.

I know the regulars on here are super familiar with all of the problems above. I just fixed both of them so I want to put them up here for any Hybrid owners who maybe are less informed on these issues. One fix? Really expensive. The other fix? Dirt cheap.

The bumping and shuddering was entirely fixed by replacing the hybrid battery. I didn't need to touch the aux trans pump, reset the ECU, or anything. I used GreenBeanBattery - it cost $2950 out the door. I paid the money for the battery (they also do a 0% interest if you pay off in full in 6 months through Paypal, which I believe they recently added), and that Saturday, somebody arrived at my house (I live in Southern California) and replaced the battery in 25 minutes. I almost wish I had found a battery online and did it myself - it is legitimately like 9 bolts to pull the battery. The battery is MASSIVELY heavy, I helped the dude carry it out of the car so my trunk didn't get scratched. But he dropped the new battery in, I drove it around the block, it ran beautifully, he left. Super simple process, and GBB has a 5 year unlimited mile warranty. Can't beat it. The big thing with these batteries is that the 300v battery powers just about everything on this truck, auxiliary transmission pump included

The oil pressure question was solved by replacing a screen located underneath the oil pressure sensor. you can find a link for the part here. Lots of videos on youtube show you how to do it- I got my hands around the sensor and tried for like two hours to get it unplugged, but something was up with mine and it was stuck. I took it to a shop and they charged me $100 which I was fine with, they told me they had trouble getting it off too. But chunks of oil clogged the filter, and it was lowering the pressure. Boom, immediately my pressure is up to approx 60 on cold start, highway hovers a little above 40. Idles around 35.

All that's left for me is a little rip in the driver's seat I have to get reupholstered. Then I'm finally at 100%. I wanted to post this stuff here just to add to the body of knowledge we have on these Hybrids. I used to own a Land Rover- those things were riddled with issues so there was a massive online presence addressing each one meticulously. These trucks seem pretty bulletproof aside from the battery failure but it still helps for anyone having trouble to see their options. If anybody's got questions with symptoms or anything ask away.
 
  #2  
Old 04-01-2019, 08:18 AM
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Default Re: 2009 Tahoe bump / shudder / jerk, P0AC4 P0BBD + low oil pressure fixes

Your post is very timely for me...noticed my oil pressure has creeped below 40 this winter once the engine warms up and at highway speeds. At cold temps the pressure gets up to 60 but was starting to get alarmed I was losing pressure (no oil loss or burning though). Probably dislodged some sludge when doing my last oil change (ran some seafoam through the oil just before the change). Will give the screen change a try and see where that goes.
 
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Old 04-01-2019, 07:12 PM
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Default Re: 2009 Tahoe bump / shudder / jerk, P0AC4 P0BBD + low oil pressure fixes

Originally Posted by SonomaGTLS6 View Post
Your post is very timely for me...noticed my oil pressure has creeped below 40 this winter once the engine warms up and at highway speeds. At cold temps the pressure gets up to 60 but was starting to get alarmed I was losing pressure (no oil loss or burning though). Probably dislodged some sludge when doing my last oil change (ran some seafoam through the oil just before the change). Will give the screen change a try and see where that goes.
The seafoam could certainly have done something. This is a quick and easy fix. My truck had 95k when I did this oil filter swap, I bought the car at 92k and by the look of the filter it had never been switched before, it was about 60% clogged. If your gauge is working properly (i.e. not fluctuating instantly to max and minimum, or acting erratic, just showing slightly lower oil pressure numbers) I would be inclined to believe that it's a clogged filter.
 
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Old 04-02-2019, 04:52 AM
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Default Re: 2009 Tahoe bump / shudder / jerk, P0AC4 P0BBD + low oil pressure fixes

The odd thing about mine is that it also fluctuates based on when AFM is active or not. It's probably a good 5-8 PSI swing depending on which mode I'm in. No noises or anything abnormal going on. I am under warranty for another 8k miles and 2 months so I'm curious if there could be something else happening.
 
  #5  
Old 04-02-2019, 01:05 PM
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Default Re: 2009 Tahoe bump / shudder / jerk, P0AC4 P0BBD + low oil pressure fixes

Originally Posted by SonomaGTLS6 View Post
The odd thing about mine is that it also fluctuates based on when AFM is active or not. It's probably a good 5-8 PSI swing depending on which mode I'm in. No noises or anything abnormal going on. I am under warranty for another 8k miles and 2 months so I'm curious if there could be something else happening.
I would take it into the dealer if it's still under warranty just to be sure, the dash gauge is one thing but a mechanical test will tell you the true results. The oil filter that I'm describing directly affects flow to the the valve lifters, so it would logically make sense if it was a clogged filter affecting your lifters, and it is possible that flow is restricted when switching between V4 and V8.

I would also suggest to you to delete AFM on your truck. While you do get noticeably higher gas mileage, especially after 100k the AFM will collapse lifters, and if you're not careful you could wear down and ruin a camshaft which is an expensive *** repair. Range Technology sells an OBD2 plug-in device for $170. You plug it into your OBD2 port, wait till the light turns solid yellow, and boom, you're permanently in V8 mode. No codes or anything. I use it on mine, and it's good to have the peace of mind.
 
  #6  
Old 04-02-2019, 01:06 PM
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Default Re: 2009 Tahoe bump / shudder / jerk, P0AC4 P0BBD + low oil pressure fixes

Originally Posted by SonomaGTLS6 View Post
Your post is very timely for me...noticed my oil pressure has creeped below 40 this winter once the engine warms up and at highway speeds. At cold temps the pressure gets up to 60 but was starting to get alarmed I was losing pressure (no oil loss or burning though). Probably dislodged some sludge when doing my last oil change (ran some seafoam through the oil just before the change). Will give the screen change a try and see where that goes.
70-75 PSI cold start 52PSI warmed up idle.. 85,500 miles on it
 

Last edited by Tahoe_08; 04-02-2019 at 01:42 PM.
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