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2011 CTS and 2007 XLR-V
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Discussion Starter #1
I accidentally managed to turn-off my 2011 CTS AWD yesterday morning during a light snow fall. Was using manu-matic to stay in lowest gear and got a message that I had activated sport mode and that AWD was turned off. Owners manual referred to sport mode (delayed up-shifts) but no comment about turning off AWD. During lunch break, returned to car and defaults had turned AWD back on. Lesson learned-RWD is not as effective on slippery roads, huh!?
 

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Hmm.. interesting!
According to the Service Manual for the 2011 CTS:

If the AWD Off Indicator needs to be turned on the transfer case shift control module sends a signal via the serial data line to the BCM which then sends a message to the instrument panel asking the I/P to command the AWD Off Indicator. The AWD Off Indicator is turned on for three reasons:
- the transfer case has overheated, or...
- the transfer case has lost both rear wheel speeds and vehicle speed, or...
- the transfer case has lost the front wheel speeds

There's no mention of deactivation of AWD by way of manu-matic shift action in Sport Mode.
 

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Discussion Starter #7
The only abnormal event during my accidental 'AWD turn off' event was perhaps some wheel-slip or brake-caused wheel-lock on slick roads at very slow speeds on my way to work. My intent to was to get to lowest gear (to first '1') to get engine-braking assist while descending my neighborhood hill on snow. Seemed to be the variable which activated sport mode and turned off AWD. Probably coincidental events and perhaps not related to each other; I have not tried to re-enact or duplicate the result.
 

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I would imagine removing the 'All-Wheel Drive' fuse at the underhood fuse block would "disable" AWD, in one manner or another.
I've never tried that with my 2011 CTS4. I wonder what the actual effect of that would be? Maybe it would help improve my fuel mileage for times when I don't really need to have AWD engaged (i.e. spring/summer/fall). LOL!
 

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2009 Cadillac CTS4
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The AWD drivetrain is mechanically connected, simply pulling a fuse will not disable it. There is no way for the driver to disable the system like you have for TCS/Stabilitrak.

The computer, however, has the ability to disable the AWD system if it detects certain conditions that could damage/destroy something. Overheating, too much torque getting thrown toward the front wheels, abusive driving, etc.

The OP likely set off a condition that warranted disabling the system....downshifting into first from a higher gear/speed on slick surfaces while AWD may have been trying to shift torque around.
 

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^ somedaycts - with that said, if the computer has the ability to disable the AWD system, what is it that it's actually disabling? As you mentioned, the AWD drivetrain is mechanically connected.
As a side note.. in normal/enabled operation, the AWD system on the 2nd Gen CTS is able to apportion 100% of torque to the front wheels or 100% of torque to the rear wheels or any other apportioning percentage ratio in between those two extremes.
 

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^ somedaycts - with that said, if the computer has the ability to disable the AWD system, what is it that it's actually disabling? As you mentioned, the AWD drivetrain is mechanically connected.
I can't say for certain, but my "engineering assumption" is as follows...

The CTS has an active transfer case with its own control module, and was designed to integrate seamlessly with ABS/TCS/Stabilitrak. It regularly monitors a variety of vehicle metrics, and through a multi-plate clutch system it can dynamically shift torque to the front wheels. If the electronics detect a problem (loss of vehicle/wheel speed, overheating, certain electrical conditions), the control module can tell the transfer case to disengage power to the front wheels...though I'm not sure what exactly disconnects. This is a "fail safe" to prevent mechanical damage to the drivetrain.

On a related note, the owner's manual states in bold that AWD models must be towed with all wheels off the ground or damage to the drivetrain can result.
 

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2008 CTS4 DI Premium (SOLD) / 2013 XTS Luxury (TOTALLED) / 2015 BMW 328i XDrive Lux
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I can disable AWD in my vehicle before I start it using the gear shift if I move it up, down, up, down, left, right, left, right, B, A, B, A, select, then the start button. I get unlimited fuel too. Works great!
Lol, this isn't a Nintendo game! (your code is very close to the original Contra game) You cracked me up on this one though:D
 

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FYI for all -
A Development Engineer /friend at GM (who was responsible for the development of the AWD system on the CTS4) kindly emailed to me some interesting information regarding AWD on the 2nd gen CTS, as well as additional info about AWD systems on other passenger vehicles. Here's a copy/paste of the info he provided:

Removing the fuse or any type of default in the CTS AWD system effectively results in a rear wheel drive (100%) vehicle. The reason is internally the transfer case has what is referred to as a one piece main shaft so any power coming into the transfer case is ALWAYS going to the rear wheels. When the system is operating as intended (AWD enabled) torque is distributed to the front propshaft via a clutch pack which is splined to the mainshaft and through a set of chain and sprockets.

With most passenger car AWD systems the secondary axle and propshaft are typically engaged full time meaning there is no front axle disconnect such as in truck 4WD systems. As a result the secondary axle and propshaft (i.e. with most of the other AWD systems) are always spinning regardless of whether the transfer case is transferring torque. So if you were to shut the transfer case off with a switch or fuse there is not a lot at all to be gained in terms of fuel economy due to the inertia and spin losses associated with the front driveline components.

Of course a (manually activated) front axle disconnect could be designed into a vehicle as a few manufacturers have done but that adds cost, mass, and potentially packaging issues. Then it also becomes a case of how much energy (gas mileage) could be saved and should the vehicle really be classified as AWD since that typically infers that a customer never has to turn a switch or knob to transfer torque to engage a secondary axle.


From the info provided, it can be inferred that some energy could be saved (gas mileage improved) on an all-wheel drive CTS via a front axle disconnect... and a front axle disconnect (resulting in RWD only operation) is achieved immediately by pulling the AWD fuse. This definitely warrants further investigation and some trials going forward! ;)
 

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I'd love to get more mileage out of a tank of gas. I didn't expect to drop from 23 mpg average in my Pontiac (SSEi w/supercharged 3800) to 18 mpg average with N/A 3.6 DI and AWD. N/A vs supercharger, N/A should get better mpgs. 3.6 vs 3.8, it's a wash. DI vs port injected, DI should get better mpg's. AWD vs FWD, FWD should get better mpg's. But to have AWD negate the gains of N/A and DI...wow, just didn't expect that.
 

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HurstGN,

Not sure why you are experiencing low mileage...I personally average about 23MPG with mostly fast highway driving. The CTS has one of the best AWD systems around with minimal mileage penalty compared to almost anything back in 2008.

http://www.cadillacforums.com/forums/2008-cadillac-cts-general-discussion/149503-awd-system-information.html

From one of the Caddilac engineers lurking in the forum:

"Doug I had a detailed lengthy response wrote last Friday and somehow it got blown away. I'll try again. The 25/75 front/rear torque split in our marketing literature can be confusing because of the type of AWD system on the CTS. Let me digress a second. There are many different AWD systems with different manufacturers and until lately the most popular was a transfer case with an open center differential. This system by design involves a fixed front/rear torque split of typically 40/60 but can really be tailored to the desired characteristics of the vehicle as you noted with as little as 5/95.

The Borg Warner active transfer case in the CTS uses a clutch pack instead of a differential which allows an infinitely variable front/rear ratio with the ability to transfer 100% of available torque to the front axle in conditions where the rear wheels may be slipping. It would take me pages to explain the control algorithms but in a nutshell, the system is continually monitoring and adjusting the clutch pack based on the input of sensors such as the throttle, steering wheel angle, yaw sensor, wheel speed sensors, engine torque, transmission gear state, etc. There are many advantages this system has over open center differentials although it is far more complex.

Now back to your 25/75 question.....the transfer case in the CTS is ONLY 25/75 DURING STEADY STATE DRIVING. This split was derived from a lot of development testing to determine what ratio provides optimum traction and handling on both high and low coefficient surfaces without transmitting so much torque to the front axle that fuel economy suffers. I'm not qualified to answer why we're so much better than AWD competitors on fuel economy but as you pointed out the 3.23 axle ratio certainly helps. Additionally, as you can imagine in this time of high cost fuel, we are constantly being challenged to improve component/driveline efficiency. The oil used in the transfer case is Mobil LT and is not synthetic but has been designed to provide great service life and performance under extreme conditions. Hope this helps and if there's something more specific you're wondering about let me know."
 

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sethjamesrimrodt said:
Has anyone drove around without the fuse in much? I'm a little worried about long turn damage. I pulled my fuse a few minutes ago and wow it's fun.
Seriously?! I believe you're the first to do that...props to you sir for taking the risk! I say that but I'm sure it won't do any permanent damage to the system...it's supposed to just disable the AWD. Does the DIC override anything else such as the speedo with a warning? Any other fault lights when you did that?

How much more fun is it? I just may have to pull the fuse myself to find out...lol.
 
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