I'm a new user of this website. It has been a wealth of knowledge.

Before anyone says the obvious, I understand that it wasn't a really bright idea to bring a used hybrid Tahoe down to Honduras. I have owned the truck since it was new and never once had it in the shop. It was so reliable that I was lured into believing that it was bullet-proof.

I have been having progressively more serious problems starting last year. Here is a summary.
4/17 Very hot day. Shifted the car into drive and got a very loud and hard shuddering from under the car. Turned the car off and started it again without any issues.
7/17 Again, super hot day. Same shuddering. No check engine light.
11/17 Occasionally experiencing no movement after shifting into drive.
11/17 Beginning to feel shuddering while driving. Engine light on. Among the codes P0004 fuel volume regulator control circuit. Also, codes for throttle body position sensor and accelerator pedal position. Replaced fuel pump, TBPS, and accelerator pedal and battery. Shuddering continues.
12/17 Shuddering worse. Can here a rattling underneath car. Possibly from transmission. At speed, engine light flashing. Mileage down to 7 mpg. Warnings now for Stabilitrack and Service Brakes Soon.
2/18 All the problems continue. Car stalled going up a hill (cool night). Would start, but then die when shifting to Drive. After short wait time, started and shifted normally.
3/18 Hearing much louder rattling under car. Car stalled on road and would die when shifted into gear. Towed home. Broke the tow chain once. Feels like brakes are engaged. Now will not crank.
Codes
P0523
P0AC4
C1209
P0B6A
P0BBD

After reading a ton of threads on this website, my thought is that the hybrid battery is bad. Having said that, I am reticent to buy a battery without verifying that this will resolve the issue.

Are there any Hybrid experts that can provide some advice?

 

A P0BBD is often HV battery. Flashing Check Engine Light is misfire. Should be P0300 or more in codes.

 

Thanks, Hillbilly. I did get a p0300 code for cyl 3 and I replaced the coil (forgot to add that!) . The engine flashing continued and the code changed to random misfire. I suspect that I have a few things going on at the same time. Would you expect that a bad drive battery would cause the rattling sound underneath?

BTW, I really appreciate the help with this.

 

The battery will cause odd behavior not so much rattling sound.


Rattle with engine running only?


To isolate the general location of noises I use a 4-to-6 foot long piece of 3/4 inch hose.


Put an ear plug in one ear. Put one end of the hose up to the other ear. Use the away end of the hose to search for the noise.

 

Rattling only happens when the engine is running. It is definitely in the area of the transmission. I can't verify exactly where now because the engine won't crank.

I checked the DIC and it shows the drive battery at 12 volts. Is there any way to charge the drive battery if the engine won't start? If that's a really stupid question, feel free to shame.....

 

If the HV battery goes too low, you can not charge it using Service Tool. Earlier models 08/09 had something called Jump Assist.


The DIC will not tell you the state of the HV battery.