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Re: TCS Ctrl Warning
Posted by David Prantl (more from David Prantl) on Tue, 6 Nov 2001 17:38:23
In Reply to: , Kok Chen, Sat, 17 Dec 1988 12:00:00 

>  '93 9000CSE turbo (auto) flashed the 'TCS ctrl'  warning light twice in 
>past two weeks.

It's all designed to confuse the normal SAAB driver, and even the normal 
SAAB technician !

Your car has an electronic throttle system (ETS).  Under normal conditions, 
it translates gas-pedal motion into an electronic signal, interprets this 
signal in a brain-box that lives under the driver's seat, and sends another 
signal to a servomotor in the throttle body that controls the throttle flap 
opening.

All this complicated (and expen$ive) ETS circuitry is there so that the car 
can override your gas-pedal input and reduce the throttle opening when a 
front wheel starts to slip from too much applied power.  This process is 
called Traction Control (TCS).

Unfortunately, the various components of the ETS eventually wear out and 
start malfunctioning.  When the brain-box comes across certain types of 
problems, it kicks the system into 'limp-home' mode, and throttle control is 
lost.

>  Each time I had to pull over as soon as I can since  throttle control was 
>inhibited immediately and I was  barely able to maintain 30mph.

There is a back-up throttle cable in the car, and when ETS goes into 
limp-home, this cable can be 'activated' by fully releasing the gas pedal.  
Once you do this (assuming the engine doesn't stall inthe process), limited 
throttle control is restored, and the car can be driven for a virutally 
unlimited distance and at speeds up to at least 100mph.  Driving in 
limp-home mode is difficult though, as the engine tends to stall everytime 
you come to a full stop.  Other limp-home features are no air-conditioning, 
no cruise-control, base-boost only from the turbo.

>  After pulling over and shutting down then re-starting  the car, 
>everything worked fine and the light stayed off.

Fortunately, more often than not, turning the car off and restarting it will 
make the limp-home mode go away, because the fault that caused it is not 
serious enough to force a 'permanent' limp-home condition.  This is what is 
happening to your car.

>  When I checked in the owner's manual I was *shocked* to  find the manual 
>describing exactly everything that  happened (and that I did the right 
>thing), and stated
>  if the warning light stays off afterwards then the car  is fine, 
>otherwise if the light stays on then have the  Saab dealer inspect 
>immediately.

It was nice of SAAB to include ETS limp-home info in the manual, but they 
were probably under the impression that this condition would be extremely 
rare.  It turns out that it is actually pretty common in cars that have ETS 
('92-'95 9000 turbo cars with the TCS option).  SAAB figured out how 
frustrating and unreliable ETS was, and 1995 was the mast model-year it was 
offered in the USA.

>  Nevertheless the experience irked me as I've only owned  the car for just 
>over two weeks,

We had the same experience with our '93, except our went into permanent 
limp-home mode (not cured by turning off and restarting), 500 miles away 
from home (no cruise), in the heat of the summer (no A/C) !

>  What is the best way(s) to prevent this from happening again ?

First, visit a competent SAAB technician that has access to a Tech-II scan 
tool and a set of factory service manuals (or at least the Traction Control 
section of the manuals).  Have them read and clear-out the ETS error codes 
(stored in memory), interpret these codes, and replace the component(s) that 
caused the codes to appear.  Then have them perform the ETS calibration 
procedure, which has been revised by SAAB several times over the years.  
Don't put this off for too long.  Limp-home mode will keep coming back, 
probably with greater frequency, and eventually will become 'permanent', at 
which point you might need to have the car towed.

>  I've heard '95 and later models allowed users to disable  TCS but earlier 
>models don't have the on/off switch.  If  this TCS problem persists should 
>I have my TCS disabled
>  by a Saab mechanic ?

The TCS function can be turned off in most TCS-equipped cars with the 
addition of an off switch.  This will allow the driver to spin the front 
wheels, but that's about it.  The faults you are experiencing are in the ETS 
system (electronic throttle), and this system cannot be bypassed.  Even when 
TCS is off, ETS still provides the interface between the gas pedal and the 
throttle flap.  The only way to get the car to behave consistently and 
reliably is to make sure that every ETS component is in good condition, and 
that the system is properly calibrated.

It is (theoretically) possible to retrofit an ETS car with a standard 
cable-throttle system, such as that found in all USA '86-'91, and '96-'98 
(and a precious few '93-'95) 9000 turbo cars, but this requires 
swapping/adding many components and modifying/adding wiring harnesses.  It 
costs about as much in junkyard parts to get rid of ETS as it (normally) 
does to fix it with new parts, takes dozens of labor-hours to complete, and 
is completely undocumented.

David Prantl
david_prantlno39sdcx6spamx782hotmail.com
'84 900S, 5M, 210kMi, RIP as of 2/98
'89 900, 3A, 116kMi, restored and SOLD on 3/24/01
'86 9000T, 5M, 190kMi
'88 9000S, 5M, 142kMi
'90 9000S, 4A, 133kMi
'93 9000CSET, 5M, 74kMi, converted from ETS to standard throttle
'97 9000CSET, 5M, 60kMi
'68 97 Sonett V4, 4M, 76kMi, #000467

Posts in this Thread:
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