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Re: Brake light switch--Christmas tree lights culprit? Posted by bobc [Email] (#473) [Profile/Gallery] (more from bobc) on Tue, 17 Sep 2019 07:07:38 In Reply to: Brake light switch--Christmas tree lights culprit?, AK Saab, Tue, 17 Sep 2019 00:34:16 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The fact is that the christmas tree symptom does not point to a single culprit. I'd say that when these cars were younger, the christmas tree symptom was most likely a failed ABS Module. However now that the cars are aging the fault could be any one of a number of problems. And if your symptom has been present for 3 years its possible that you have multiple failures.
I had the same symptom on my '01 Aero. Uncharacteristically I mistakenly tried the "easy way" (just replace stuff). I had the abs module rebuilt, no change. I swapped out the brake switch, no change. I even rebuilt the junction under the rear seat (also a common failure)
I finally had to properly diagnose and trace the faults. Turns out the connector at the wheel speed sensor had failed. Not only that, but it's failure allowed moisture and corrosion into the wire. Replacing the connector was not enough ... I had to replace at least 2 ft of wire (I ended up replacing the entire run from the junction to the sensor)
Do you have access to a Tech 2? There are some "professional grade" (SnapOn, etc) that can read Saab ABS codes, you may have a nearby friendly mechanic that can check. If you are near NC I can help.
If no access to the codes consider these failure modes that can lead to the christmas tree effect:
1 - abs module (ruled out)
2 - brake light switch (inexpensive and easy .. I dont have a write up but aside from the contortions to get to it its a 1/4 turn and it pops out.
3 - check each wheel sensor resistance with ohm meter, they should all be about the same
4 - rebuild junctions J108-J111 (Rear wheel ABS sensor wiring)
5 - tone ring on front wheels (it can crack or get gunked up)
my thread: https://www.saabnet.com/tsn/bb/9-5/index.html?bID=278328
_______________________________________ '08 9⁵ 2.3T SportCombi, Polar White '01 9⁵ Aero Midnight Blue (benched) '00 9⁵ Aero Midnight Blue (rescued) '99 9⁵ Base model, Cosmic blue '00 9⁵ Aero Silver (RIP - transmission )
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