2009 Tahoe P06AF code (torque management system forced engine shutdown)

[MuleDog]

My 2009 Tahoe Hybrid has 97,000 miles and has not had any hybrid issues since I have owned if the past 4 years. I only use it occasionally and only put about 4,000 miles per year on the vehicle.

The issue first developed after I had left a phone charger in the vehicle overnight so the starting battery was run down. I noticed the Check Engine light as I jump started the vehicle. It would not start until I removed the battery terminal connections, cleaned them and charged the battery for 30 minutes. It then started but ran very rough and I connected my scanner and pulled codes P0AC4 (Hybrid/EV powertrain control requests MIL illumination) and P06AF (torque management system forced engine shutdown). After running for a few minutes, the engine ran normally and I noted the vehicle reported 14 to 15V charging. I could not clear the codes with my scanner. I needed to return home so drove (nervously) 300 miles with the codes. Now the vehicle will not crank and codes remain.

I am expecting this is either a connection problem or a hybrid battery pack issue. What are your troubleshooting suggestions?

 

[swathdiver]

@BG1988

I would suspect that the vehicle battery is the issue. It seems to have a very low state of charge and either needs to be put on a tender for a while to be rejuvenated or replaced. The alternator charging at near full output is the clue for me. It's trying to keep you from getting stuck with a discharged battery.

When the vehicle battery is weak, it causes all kinds of codes to be thrown and other anomalies.

 

[Joseph Garcia]

Before firing the parts cannon, get the battery's health confirmed. The only true way to test a battery is to pull it out of the truck, take it to an auto parts/battery store with a bench load tester, and get it load tested. Have you done that? If not, do it now, before proceeding any further with its associated extra costs.

 

[j91z28d1]

when you get codes like that n this hybrid where a module is requesting a check engine light. a decent scanner like the clone tech 2 for about 300$ or even some of the dongles like the topdon which is 70ish $ last time I saw but has a yearly subscription. or the gear wrench that's 150$ but no subscription.

basically a good scanner that can read the fault codes from the module directly, and even more useful is the snap shot of what was happening when the code was set. that goes a long way to sorting out what actually happened and then you can clear the codes and see if they come back.

like the others i would guess it was the dead 12v battery that caused the issue. better said the voltage drop while in the middle of trying to spin the engine over. as a reminder, these do not have a conventional alternator or a starter. the 300v hybrid battery powers the front electric motor inside the tranny that spins the engine over during cranking and the 300v DC inverter charges the 12v battery.

while the 300v battery spins the engine over, everything that controls that 300v, the contactors, relays and moduals all run off the 12v battery. so if the 12v battery voltage drops at the wrong time, everything kinda freaks out and goes into safety mode. the primary objective of everything is to keep that 300v DC isolated away from everything, including the human that might be touching something metal. so isolation checks are done before every crank request. there's even a code that if the truck thinks it's been in any kinda accident it will set a fault code and not activat the hybrid battery contactors. there have been cases of guys sitting this code for everything from giant pot holes to trying to jump start a dead battery. once set it will not start till cleared.

for your truck, it sounds like it sits for a while between drives, if you can find the supplemental owners manual it will give you the time frame for parking and storage. these trucks have quick disconnects on the 12v battery because if you're going to let it sit a certain amount of time, the manual says to remove the terminals. I forget the details but it's in there and probably good to follow. being yours doesn't get driven much and then run down to dead. i wouldn't waste your time getting the 12v battery load tested. Just replace it. those little hand held testers are designed with regular starters in mind. our trucks use the 12v battery In a completely different way, almost more like a deep cycle marine battery than a high cold cranking amp battery. one it seems can test fine with the quick auto parts store tester but the truck isn't happy with.

replace battery, find good scanner to read codes, write them down and try to see what the snap shot shows and then clear the codes and you'll probably be fine.

 

[BG1988]

Before firing the parts cannon, get the battery's health confirmed. The only true way to test a battery is to pull it out of the truck, take it to an auto parts/battery store with a bench load tester, and get it load tested. Have you done that? If not, do it now, before proceeding any further with its associated extra costs.

yes most likely the hybrid battery

when i pulled the hybrid battery one of the modules barely had 98mAh


few charge/discharge cycles got it to 1,000mAH capacity

you will need some

Salisbury linesman gloves rated to 1,000 volts and leather linesman glove protector..

once all 40 nuts are off it should be safe to handle as the voltage drops to 7.5 volts