This old Tahoe Hybrid makes me smile every time I jump in in to drive off.....................
Great information RyeTom. Thanks for posting and thank you very much for following up. Not a huge amount of information on the GM Two Mode Hybrids out on the web but from everything that I have seen so far the battery management system that they developed is pretty good and most of these batteries are lasting a very long time. I wish I knew more about it but it sounds like they are simply keeping the battery from overcharging too much and then preventing it from discharging too much i guess that keeps it in a sweet spot so it lasts longer? Now if I can just find a youtube video showing me how to check the cooling fan on my 09 I will put that on my list to check plus I REALLY WANT TO SEE THE BATTERY Hahahaha.

 

what kind of control module did it need? Was it a module inside the hybrid battery?

 

 

my 2009 hybrid Tahoe the battery under the hood went dead. Replaced the battery and now it won't start and is throwing the service hybrid system code. Hooked a snap on scan tool to it and it said that the hybrid battery is over charged. I decharged all 40 cell batterys to 6.9 volts. The computer still says the hybrid battery is still over charged. Hopefully replacing the module will work.

 

What were the codes you got from the snap on scan tool?

 

THE GUY SAID THAT THE HYBRID BATTERY WAS STILL SAYING IT WAS OVER CHARGED AND THAT HE COUNDNT GET ANY further than that. Almost like the truck was in in lock out safety mode because of it.

 

I'm looking at the service manual and don't see any diagnostic codes that say that the hybrid battery is "overcharged". Is it possible the mechanic is misinterpreting the diagnostic trouble code description in the Snap On tool? Did your Tahoe work correctly before the 12V battery died? If so, I highly doubt your High Voltage hybrid battery is at fault. There is a P0563 "System Voltage Too High" that is actually the 12V battery voltage, not the hybrid battery voltage. One of the conditions that can cause that code is if a charger was plugged into the 12V battery with the Tahoe system On and it detected higher voltage than normal in the hybrid powertrain control module (HPCM). This code is set when "The HPCM detects system voltage [on the Ignition voltage circuits] is 18 volts or greater for 5 out of 6 seconds." Read the voltage to the Hybrid Powertrain Control module with the Ignition On. It is possible the power inverter module (PIM) may be bad.

 

that does make since. Cause the battery died when the truck was out of town and they tired to jump start it with another car. I will try to test the things you talked about and get back with you. Thanks very much.

 

it's under dash

 

#PIT4585E: 2-MODE (HYBRID) No Crank After Discharged Or Dead 12v Battery - (Nov 16, 2012)

Anytime a battery charger or booster pack is connected to the 12V battery, the ignition key should always be in the off position. If this recommendation is not followed, the Serial Data Gateway Module (SDGM) may not report "Crash Sense Failed" and the 300v Hybrid Battery Contactors will remain open until the Hybrid Powertrain Control Module's (HPCM) High Voltage (HV) DTCs are reset.

To reset the HPCM HV DTCs, please use the following procedure:

1. Make sure the 12 volt battery is fully charged.
2. Clear DTCs in all modules.
3. Under the Body Menu of the Tech2 select the SDGM Special Functions Menu.
4. Select the "Crash Sensor Reset" in the SDGM by pressing “Enter” then select “Exit” to the Powertrain Menu.
5. Access the HPCM Special Functions Menu.
6. Select "Clear 300V Impact Detection DTC" and press the “Reset” soft key at the bottom of the screen. Exit to the Special Functions Menu.
7. Select the "Clear 300V Present DTC" screen and press the “Reset” soft key at the bottom of the screen. Exit the Special Functions Menu.
8. Turn the ignition key to the "OFF" position.
9. Power "Off" the Tech 2 scan tool and disconnect it from the vehicles diagnostic connector.
10. Open and then close the Driver's Door to disable the Retained Accessory Power (RAP).
11. Wait for 3 minutes and then start the vehicle.

Note: If there is a P0C76 setting, disconnect the 12v battery. With both 12v battery cables disconnected from the battery, discharge the capacitors by holding the cables together for 15 seconds. Reconnect the 12v battery and perform the above procedure again. If the DTC still resets, follow SI diagnostics and call the General Motors Technical Assistance Center if needed.


ADDITIONAL SI KEYWORDSIT4585 draw drain electrical engine HCP M99 mode nocrank proactive SDG two unwanted voltage

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.