'99 A8 Traction Control System
09-21-2011, 04:05 AM
#1
Audiworld Junior Member
Thread Starter
'99 A8 Traction Control System
Doesn't the A8 have a traction control system that works on all 4 wheels? If one side slips it should apply the brakes to the spinning wheel, thereby shifting power to the opposite side? Is there a warning light on the dash that flashes when the system is active?
On my car I cannot get this light to come on, and don't feel the usual ABS pulsing when a traction system is operating.
Last season I went into an icy, empty parking lot and got on the gas hard, spun the car around sideways, etc...couldn't get that light to come on.
What causes this system to not operate?
On my car I cannot get this light to come on, and don't feel the usual ABS pulsing when a traction system is operating.
Last season I went into an icy, empty parking lot and got on the gas hard, spun the car around sideways, etc...couldn't get that light to come on.
What causes this system to not operate?
09-21-2011, 11:33 AM
#2
AudiWorld Super User
Doesn't the A8 have a traction control system that works on all 4 wheels? If one side slips it should apply the brakes to the spinning wheel, thereby shifting power to the opposite side? Is there a warning light on the dash that flashes when the system is active?
On my car I cannot get this light to come on, and don't feel the usual ABS pulsing when a traction system is operating.
Last season I went into an icy, empty parking lot and got on the gas hard, spun the car around sideways, etc...couldn't get that light to come on.
What causes this system to not operate?
On my car I cannot get this light to come on, and don't feel the usual ABS pulsing when a traction system is operating.
Last season I went into an icy, empty parking lot and got on the gas hard, spun the car around sideways, etc...couldn't get that light to come on.
What causes this system to not operate?
FWD versions (3.7L) have ASR (anti slip regulation, through reduced engine power + ABS controlled EDL) and an ASR light that flashes during intervention.
ASR is not present on your car (32V 4.2 Q)...just "ABS for Quattro", which is ABS controlled "EDL" front and rear, but no ASR.
Facelift (2000 & up 40V) have ESP, which is front & rear EDL + electronic throttle intervention for traction control ( not to mention other sensors for stability control functions) and has a flashing ESP "symbol" during any traction control, braking OR stability intervention.
Don't have a pre-facelift D2 to inspect, but Bentley manual shows no mention of an a flashing intervention light for 97-99 A8 Q's...only the FWD with ASR & later ESP systems.
Though, you definitely should FEEL (hear) the vibrating ABS single brake intervention during traction control intervention,
especially I believe under 25mph. This is all controlled through the same ABS wheel speed sensors at all 4 wheels...they read off "serrated slots" cut into each of the 4 outer cv joints. These sensors can get dirty, corrode, have wiring problems or outright fail. They all send signals to the ABS computer (in car) which in turn sends correction signal to the ABS hydraulic unit under the hood. Normally, if the ABS hydraulic unit has an electrical or other failure, you'll get a solid ABS warning light. Failed wheel sensors need to be physically checked or a VAGcom diagnostic check. The ABS computer rarely fail and "should" show an ABS failure warning on the dash.
Does your ABS seem to work during braking? ...wet road or gravel...should be noticeable vibration.
Last edited by silverd2; 09-21-2011 at 11:36 AM.
09-21-2011, 11:37 AM
#3
Audiworld Junior Member
Thread Starter
ABS does work well. I couldn't seem to notice the ABS pulsating or the usual noise during my last test. Probably have to wait for it to snow again to find out. Just seems odd, all other cars I've had w/ traction control (Jetta, EuroVan, Land Rover, etc) all flash a light at you. I'll shine a bright light at the instruments and see if any such symbol exists in the cluster.
09-21-2011, 11:53 AM
#4
AudiWorld Super User
ABS does work well. I couldn't seem to notice the ABS pulsating or the usual noise during my last test. Probably have to wait for it to snow again to find out. Just seems odd, all other cars I've had w/ traction control (Jetta, EuroVan, Land Rover, etc) all flash a light at you. I'll shine a bright light at the instruments and see if any such symbol exists in the cluster.
My B5 had electronic throttle, so ASR worked through throttle cut off, if it detected both drive wheels spinning after first applying the EDL system.
FWD A8's had cable throttle, so applied their version of ASR by cutting engine power through timing retard and possibly other "cut-offs"(?) ...not sure if it went farther than that.
With all working normal and good tires, the regular braking works so well that we rarely kick in the actual ABS...partly because "EBD" (electronic brake pressure distribution) works all the time, without pulsation AND independent of the regular ABS system...it keeps the rears from locking (electronically controlling pressure to the rear) like the older mechanical (attached to suspension) valves used to. EBD is an electronic "failsafe" that works EVEN with total ABS failure.
So, you may have no ABS at all and would not notice till a severe situation.
Gravel under one side and an attempted brake lock-up is a good test....or even a hard lock-up on wet pavement, with no one in the way....unless you have some snow to play with.
11-27-2011, 03:42 PM
#5
The A8 does not have traction control or stability control - 100% certain of this - as Silverds noted above. I've had my A8 in deep snow, sideways, stuck in mud etc - no traction control, no pushing the accelerator to the floor with nothing happening. The 2002 A8s did get this feature with stability control too 
- my next A8 will have this, stability control is the most important safety invention after the seatbelt.
- my next A8 will have this, stability control is the most important safety invention after the seatbelt.
11-27-2011, 04:57 PM
#6
AudiWorld Super User
The A8 does not have traction control or stability control - 100% certain of this - as Silverds noted above. I've had my A8 in deep snow, sideways, stuck in mud etc - no traction control, no pushing the accelerator to the floor with nothing happening. The 2002 A8s did get this feature with stability control too - my next A8 will have this, stability control is the most important safety invention after the seatbelt.
- my next A8 will have this, stability control is the most important safety invention after the seatbelt.97-99 FWD A8's have traction control w/EDL through the ABS and engine power intervention..called ASR (Anti-slip regulation = traction control).
97-99 Quattro just have 4 wheel drive...better than FWD with ASR.
2000-2003 D2 A8's all have EDL (electronic diff lock) = "traction control" through the ABS stopping the spinning wheel..front and rear.
All A8L's (2000 on) and A8 SWB ('00) as an option (my car, '01 A8 SWB w/ESP option) have ESP which includes stability control, EDL and electronic throttle intervention for traction control.
100% certain, huh ??
Basic guide to features:
https://www.audiworld.com/model/a8/content.shtml
11-28-2011, 04:28 AM
#7
Audiworld Junior Member
Thread Starter
OK, so according to the owners manual of my A8 (1999 4.2L Quattro) it is equipped with, as standard, front and rear "Electronic Differential Lock" (EDL) which in my opinion is your typical brake-based traction control. Using just the standard ABS components when one wheel on an axle is detected as spinning faster than the other and the brake pedal is not depressed, the ABS system will pulse the brakes on the spinning wheel. My A8 does not seem to do this. However, I'm certain ABS works. We've had about 20" of snow since October 31st this year and coming down an unplowed road I can fully apply the brakes and the ABS system operates with typically solenoid-cycling noises and varying pedal feel. But, gassing it hard will cause wheel spin on both axles, on the wheels that have the least traction. Obviously, driving in a normal manner causes no wheelspin as the 4wd traction available overcomes the weight of the car and moves it forward. But, when wheels are spinning, the EDL should intervene! I suspect the vehicle does not, in fact, have EDL.
For example, we had a 1999 EuroVan. According to the owners manual, it too had EDL on the front axle. In trying the same test, fast acceleration on an icy surface with wheels spinning, there was no intervention. However, ABS on that vehicle worked perfectly well. I concluded, despite the owner's manual, that the vehicle was not equipped with EDL. Our current 2002 EuroVan also claims to have EDL on the front axle. This one obviously does...a yellow warning lamp flashes during wheel slippage and you can hear / feel the EDL operation. However, the 2002 EV has an electronic throttle on its VR6, and has ESP. The 1999 EV had a cable and no ESP.
The 1999 A8 has a throttle cable and no ESP. I'm still going to see if there is an EDL indicator lamp in the cluster, and also check and see if there is an ABS sensor and plumbing from the ABS box to each rear wheel. Many cars with "4-wheel ABS" actually are only 3 channel, meaning the rear wheels are modulated together. If the A8 really does not have EDL, than there is really no reason to have 4-channel ABS. If I find it only does have 3-channel plumbing, than clearly it does not have EDL.
As a side note, while brake-based traction control is a great idea and very helpful, adding throttle intervention is a bad idea. My Jetta has a manual transmission and while trying to climb a steep, snow-covered road the throttle keeps reducing and reducing power until finally you stall out. Obviously switching ESP off (mostly) prevents throttle intervention, at least on a standard shift I think its a bad idea.
For example, we had a 1999 EuroVan. According to the owners manual, it too had EDL on the front axle. In trying the same test, fast acceleration on an icy surface with wheels spinning, there was no intervention. However, ABS on that vehicle worked perfectly well. I concluded, despite the owner's manual, that the vehicle was not equipped with EDL. Our current 2002 EuroVan also claims to have EDL on the front axle. This one obviously does...a yellow warning lamp flashes during wheel slippage and you can hear / feel the EDL operation. However, the 2002 EV has an electronic throttle on its VR6, and has ESP. The 1999 EV had a cable and no ESP.
The 1999 A8 has a throttle cable and no ESP. I'm still going to see if there is an EDL indicator lamp in the cluster, and also check and see if there is an ABS sensor and plumbing from the ABS box to each rear wheel. Many cars with "4-wheel ABS" actually are only 3 channel, meaning the rear wheels are modulated together. If the A8 really does not have EDL, than there is really no reason to have 4-channel ABS. If I find it only does have 3-channel plumbing, than clearly it does not have EDL.
As a side note, while brake-based traction control is a great idea and very helpful, adding throttle intervention is a bad idea. My Jetta has a manual transmission and while trying to climb a steep, snow-covered road the throttle keeps reducing and reducing power until finally you stall out. Obviously switching ESP off (mostly) prevents throttle intervention, at least on a standard shift I think its a bad idea.
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11-28-2011, 04:58 AM
#8
AudiWorld Super User
OK, so according to the owners manual of my A8 (1999 4.2L Quattro) it is equipped with, as standard, front and rear "Electronic Differential Lock" (EDL) which in my opinion is your typical brake-based traction control. Using just the standard ABS components when one wheel on an axle is detected as spinning faster than the other and the brake pedal is not depressed, the ABS system will pulse the brakes on the spinning wheel. My A8 does not seem to do this. However, I'm certain ABS works. We've had about 20" of snow since October 31st this year and coming down an unplowed road I can fully apply the brakes and the ABS system operates with typically solenoid-cycling noises and varying pedal feel. But, gassing it hard will cause wheel spin on both axles, on the wheels that have the least traction. Obviously, driving in a normal manner causes no wheelspin as the 4wd traction available overcomes the weight of the car and moves it forward. But, when wheels are spinning, the EDL should intervene! I suspect the vehicle does not, in fact, have EDL.
For example, we had a 1999 EuroVan. According to the owners manual, it too had EDL on the front axle. In trying the same test, fast acceleration on an icy surface with wheels spinning, there was no intervention. However, ABS on that vehicle worked perfectly well. I concluded, despite the owner's manual, that the vehicle was not equipped with EDL. Our current 2002 EuroVan also claims to have EDL on the front axle. This one obviously does...a yellow warning lamp flashes during wheel slippage and you can hear / feel the EDL operation. However, the 2002 EV has an electronic throttle on its VR6, and has ESP. The 1999 EV had a cable and no ESP.
The 1999 A8 has a throttle cable and no ESP. I'm still going to see if there is an EDL indicator lamp in the cluster, and also check and see if there is an ABS sensor and plumbing from the ABS box to each rear wheel. Many cars with "4-wheel ABS" actually are only 3 channel, meaning the rear wheels are modulated together. If the A8 really does not have EDL, than there is really no reason to have 4-channel ABS. If I find it only does have 3-channel plumbing, than clearly it does not have EDL.
As a side note, while brake-based traction control is a great idea and very helpful, adding throttle intervention is a bad idea. My Jetta has a manual transmission and while trying to climb a steep, snow-covered road the throttle keeps reducing and reducing power until finally you stall out. Obviously switching ESP off (mostly) prevents throttle intervention, at least on a standard shift I think its a bad idea.
For example, we had a 1999 EuroVan. According to the owners manual, it too had EDL on the front axle. In trying the same test, fast acceleration on an icy surface with wheels spinning, there was no intervention. However, ABS on that vehicle worked perfectly well. I concluded, despite the owner's manual, that the vehicle was not equipped with EDL. Our current 2002 EuroVan also claims to have EDL on the front axle. This one obviously does...a yellow warning lamp flashes during wheel slippage and you can hear / feel the EDL operation. However, the 2002 EV has an electronic throttle on its VR6, and has ESP. The 1999 EV had a cable and no ESP.
The 1999 A8 has a throttle cable and no ESP. I'm still going to see if there is an EDL indicator lamp in the cluster, and also check and see if there is an ABS sensor and plumbing from the ABS box to each rear wheel. Many cars with "4-wheel ABS" actually are only 3 channel, meaning the rear wheels are modulated together. If the A8 really does not have EDL, than there is really no reason to have 4-channel ABS. If I find it only does have 3-channel plumbing, than clearly it does not have EDL.
As a side note, while brake-based traction control is a great idea and very helpful, adding throttle intervention is a bad idea. My Jetta has a manual transmission and while trying to climb a steep, snow-covered road the throttle keeps reducing and reducing power until finally you stall out. Obviously switching ESP off (mostly) prevents throttle intervention, at least on a standard shift I think its a bad idea.
I shoulda finished my homework...the link I provided confirms that all year A8's do indeed have EDL (traction control) on all the drive wheels.
https://www.audiworld.com/model/a8/content.shtml
I can confirm also that 97-99 FWD "ASR" uses ignition retard and other management functions to cut engine power when EDL is not enough. 97-99 Quattro is EDL (front & rear) without the power intervention.
Electronic throttle on 2000 and up added throttle intervention when EDL is not enough, as part of the ESP function, which can be turned off with ESP dash switch (convenient...and fun sometimes, when ya wanna play).
What we can also confirm is that Wuffman was wrong on all points. ...sorry, just messin with you
11-28-2011, 05:23 AM
#9
AudiWorld Super User
P.S. Don't have a theory on your lack of traction control...all U.S. models are supposed to have EDL...possibly a problem in the ABS controller (computer in car or hydraulic unit under hood), but I would think you'd get an ABS problem light.
Also, from past threads on other forums and checking Bentley wiring diagrams, I don't believe 97-99 A8 Q's had any flashing dash light during EDL function.
My past B5 front FWD had a flashing ASR light (as I believe FWD A8's have?) and 2000 up with ESP have flashing ESP symbol during any ESP event (traction or stability).
Also, from past threads on other forums and checking Bentley wiring diagrams, I don't believe 97-99 A8 Q's had any flashing dash light during EDL function.
My past B5 front FWD had a flashing ASR light (as I believe FWD A8's have?) and 2000 up with ESP have flashing ESP symbol during any ESP event (traction or stability).