A strange Saab fault...

-westy-

-westy-

-westy-

Soldato
Joined
7 Nov 2002
Posts
12,605
Location
Snorbans, UK
Hello,

My car developed a very weird fault on the way to work this morning.

While driving along normally, the speedo needle suddenly drops, and the ABS sensor comes on, along with the brake warning light (which I've since found out is automatic, since the ABS light is on)

Then after a while, the speedo needle pops up again, and all the warning lights go off.

It did this on the way to work this morning, and on the way back, a few times. Apart from the obvious issue of my speedo not working, the car drove perfectly normally, apart from the lack of ABS, which wasn't a problem.

Any ideas? ABS sensor?

Thanks :)
 
I had a simular issue in my Focus that comes and goes every few weeks. After turning the engine off & all the needles on the instrument cluster go back to their resting places, the fuel gauge suddenly decides to spring back to life by going all the way around and then it will rest on the amount of fuel that I will have left. It will stay like this until I turn the engine on & then it will go back to the original resting place quickly and then to normal fuel position.

Even if I turn the car on & off again it will still do the same thing but then after a few hours when I turn engine on & off again, the problem will disappear until the next time. I have yet to find a cause to this problem but a couple of other people have suggested to me that it could be battery related too as apparently a battery which is slowly on its way out can do strange things to instrument clusters on cars - though my car always starts up fine?

Liam
 
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From what i can remember it is the nearside rear wheel sensor that supplies the speedo signal. Problems with the ABS/TC ecu can cause this exact problem as well. If the wheel sensor is duff, you should also have running issues as the engine ECU (in the case of Trionic 5 only) requires a speed signal, without this it will stall when stopping.
 
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Nope, the engine runs completely fine - the whole car behaves as normal, apart from the speedo needle not working, and the lack of ABS :)
 
Faulty ABS sensor sounds right, check all abs sensors with a multimeter and car jacked up and spin each wheel to find faulty one (Faulty one will provide you with lower reading than others).

Lack of information as to what model Saab you have, some of them can be diagnosed via OBD2 port.
 
Maz said:
Faulty ABS sensor sounds right, check all abs sensors with a multimeter and car jacked up and spin each wheel to find faulty one (Faulty one will provide you with lower reading than others).

Lack of information as to what model Saab you have, some of them can be diagnosed via OBD2 port.
Click to expand...

Oh, sorry, its a 1998/99 9-3 2.0t
 
According to Autodata you can test ABS Sensors on ABS Multi plug.

Front left being pins 6&7
Rear left being pins 8&9
Front right being pins 3&5
Front left being pins 1&2

Jack up the wheel up corresponding to the sensor you want to test, put multi meter across the appropriate pins for that sensor and get someone to spin wheel.

Typical readings should be voltage alternating by 0.1 V, resistance should be 1015 - 1245 ohms.

If you find no voltage then that sensor is likely duff.
 
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as said in my post above, if the sensor was at fault it could only be the nearside rear, but if the sensor was at fault you would get running problems as the speed signal to the main ECU would be gone. With trionic 5 engine management it is essential for correct running. (it uses it to work out correct idle when hot and for torque limitation in 1st, 2nd and reverse gears)

Therefore it is more likely to be the ABS ecu that is at fault not the wheel sensor. If you want to change the rear abs sensor you have to get a new or working used hub assembly, as the sensor is built into the hub itself.
 
Kei said:
as said in my post above, if the sensor was at fault it could only be the nearside rear, but if the sensor was at fault you would get running problems as the speed signal to the main ECU would be gone. With trionic 5 engine management it is essential for correct running. (it uses it to work out correct idle when hot and for torque limitation in 1st, 2nd and reverse gears)

Therefore it is more likely to be the ABS ecu that is at fault not the wheel sensor. If you want to change the rear abs sensor you have to get a new or working used hub assembly, as the sensor is built into the hub itself.
Click to expand...

Funnily enough, I now have running problems, with the car lacking power coming out of slow corners, to a point where I have to pull over and restart the engine so I can continue driving.
 
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