Last Sunday I took my 2008 Yukon Hybrid to the hand car wash. They cleaned up the interior, washed the car, then drove it outside where they proceeded to do the dry off and window detail.

About ten minutes into this process - with the drivers door open - suddenly the car's alarm sounds (built in GM alarm). It doesn't turn off with the remote so I get into the car to put the key into it to start it and clear the alarm.

I am able to clear the alarm, but the instrument panel lights up with error messages when I try to start the car - and it won't start. It also wont do anything else - including allow me to call onstar (why don't they have a backup for emergencies). At this point it looks as if the regular battery is completely dead. I open the hood and check everything to make sure it didn't get wet inside - it didn't.

I call GM roadside service on my cell phone. They tell me they cannot jump start a hybrid and send a flat bed - 90 minutes later they show up - and to my surprise the driver pulls out his starter battery and gives me a boost - which works.

We are able to start the car and rev it up for a while - but the moment the car goes into autostop I am dead again - can't restart - and need another jump. Probably the why GM's policy on no jumpstarting Hybrid Yukons. Luckily the roadside driver hadn't left yet.

The second time, the service guy re jumps me, and I put it in manual mode and keep my foot on the brake and gas pedal to keep it running. Driving thus in manual, (being followed by the roadside service in the flatbed) we get me to the Tustin dealer where I left the car. Note that after 15 minutes of actual driving I can now start the car normally.

From this experience, I discover that GM appears to have the same bug in their system that Toyota acknowledged with their Hybrid Highlander - namely that the system is not smart enough to keep the engine running to charge the regular battery when it is low.

As it turns out this is the second time on this vehicle that the system flatlined - even though it had been driven on a daily basis.

I am guessing that my problem might be that I drive a relatively short distance to work (about 4 miles) and have a 1-3 mile drives at lunch. In Irvine and Newport Beach California - this means lots of stops and starts with the engine autostopping regularly.

As I know from actual experience that the system requires the regular battery to start from the autostop, and does not prevent autostop when the battery charge is low - I suspect that my recurring problem is a result of the software bug allowing the battery to run exceeding low - and all it needed was to have the lights left on and the door opened by the car wash to kill it off.

Has anybody else had this problem?

How does one report this design flaw to GM so it gets their attention? (the dealer service tech didn't know how to do that). Apparently the dealer service network doesn't have a good feedback channel to GM Engineering.

 

I have never had an issue with my 2008 yukon like that and my driving is similar to your daily routine. I do know that some 2008's were shipped with the wrong 12V battery which caused some issues. they can look at your 12v and determine if it is the correct one for the hybrid.

 

Glenn

I think you could have the 08 problem of a faulty transmission control harness. Your symptoms sound similar to mine. Drive it around. Stop. And then it won't start. Leave it five minutes, and hey presto its alive again.

My Tahoe was built Jan 08 - you can find the date on the driver's door sticker. There were problems with the wiring harness to the transmission for some trucks built before April 08.
Remember its the electric motors in the transmission which start the ICE. They work when the truck is stopped and switched off, and in auto stop.
Your dealer should be able to diagnose this with the Tech2 computer.
Hope this helps.

 

Thanks - I mentioned this to the dealer to check out today.

 

I mentioned this to the dealer to check out today - however after setting for more than 30 minutes - the car did not restart without a jump to the regular battery. I am still thinking that the car should not autostop if the battery is very low.

 

I had the same problem. After complainting many times to my servise advisor, and getting stuck at the CO canal late afternoon with no help to jump start my battery, finally got me a new battery, since then, the problem dissappeared!

 

Just to clarify a couple of points from this thread:
- Yes, you can jumpstart these, and they are designed to be jumpstarted. Read the owners manual, it can even recharge the 300V battery pack off of the 12V battery during the jumpstart to allow a fully discharged 300v pack to be jumped. This is called Jump-Assist (or something like that)

- In manual mode, the vehicle will NEVER go into autostop, so you did not have to "brake-torque" it or rev the engine, just shift to manual and leave it there and you have prevented autostop. This will charge the 12V battery, and you can switch the DIC to display the 12V battery charge level to see how it is doing.

Yes, I agree that the vehicle should be programmed to never autostop on a 12V battery that does not have enough voltage to allow a restart. Seems like they should have worked that out pretty quickly in field-testing.

 

Everyone: the engine does NOT need to be running to charge the 12V battery. The system has a DC-to-DC converter that will operate ANY time propulsion is available. To verify this, turn on headlights and or wipers for a couple minutes. Go to the DIC and bring up the 12V system voltage.

It should be 14 or maybe even 15 volts in Drive, Manual, Auto-Stop, any time the system is actually running and it has propulsion torque to the wheels.

Again: the engine running has no effect on charging since there is no mechanical alternator. If the vehicle shut down (Auto-Quit), 12V charging will stop.

After headlights, wipers, and high HVAC blowers are off the 12V system should go back into fuel economy mode and drop to 12.8V or 13 on DIC.

A vehicle that has been 12V jumped will most likely not go into FE mode as it should know that the 12V needs charging. Again the DIC will show 12V voltage rounded to an integer.

 

Yes, but:
The 300V has to have a charge to charge the 12V. I've had to jump mine when the AuPair left the car in accessory (not run) for an hour while the kids watched a video waiting in a parking lot. The 12V has to have a voltage high enough to power the 12V systems for the computer to allow the vehicle to start.

Secondly, the engine charges the 300V battery, so that battery is the one that needs the engine running to charge the system. As de facto evidence on this board has shown, there are situations after a jump where the computer allows the vehicle to go into Auto Stop when it cannot recover. This could be due to a "surface charge" on the 12V battery fooling the system into thinking it has enough charge. We used to see this all the time measuring lead-acid batteries. You have to hit them with a hard discharge before measuring the voltage to get a good idea of the real cranking voltage available.

 

FJ: The 12V voltage for a no start is just above 10 volts open circuit. A "normal" 12V starter vehicle at 10V open circuit most likely will just click the solenoid. I do have questions for this forum.

1) During these non-charging events, is it actually Auto-Stop or did the vehicle quit? (OFF) There is much more than a semantic difference here.

2) During the Auto-Stop after jump does the vehicle still drive electrically? What is DIC 12V system voltage? Does the power steering still work?

3) Will shifting to "M" start the IC engine?


To drain the 12V it can take as little as 15 minutes if someone puts the vehicle in Run and does NOT start it. My wife and kids don't seem to grasp the difference between Accessory and run. It's about 20 more amps.

There are times after a 12V jump that they may quit. (Surface Charge)? The tachometer needle will indicate OFF not Auto-Stop. The vehicle won't move in electric. The DIC voltage will drop. Power steering will lose assist and be hard to steer.

I'm interested in any case.