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rhayes
New User
Aug 11, 2008, 12:16 PM
Post #1 of 2
(1409 views)
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Caddy ABS problems
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 ABS problems-'04 cadillac CTS 64k-at slow speeds the brake petal pulsated just when turning left or right. left off petal and reapply brakes seem to work ok. no problems at higher speeds. have been to several shops and show NO error codes. problem very intermitant,but does seem to happen more often.
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DanD
Veteran
/ Moderator
Aug 12, 2008, 4:27 AM
Post #2 of 2
(1398 views)
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Re: Caddy ABS problems
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This is likely a wheel speed senor. It may not be setting codes due to the sensor not going far enough out of its parameters for the electronic brake control module (EBCM) to recognize a fault but enough to set up a false ABS activation.
The wheel speed sensors on this vehicle are an integral part of the wheel bearing assembly.
If a wheel bearing is beginning to fail and become slightly loose (you may not feel the looseness by hand) that during a turn the bearing is allowed to tip slightly; due to the weight of the vehicle pushing on the bearing.
If this is what’s happening; the air gap between the sensor and the reluctor (trigger) ring opens or closes up; changing the sensors output.
The EBCM thinks it’s seeing a wheel slowing down, faster then the others and becomes active in an attempt to bring it back inline with the others.
With the use of a scan tool, set up to read wheel speed sensor speeds; a technician might be able to pick out which wheel is causing this?
I’ve also have had to use a lab scope connected to the individual sensors; road test the vehicle, while monitoring the sensors real-time wave pattern; when a scan tool was to slow to pick out the fault.
On a last resort you could start changing wheel bearing assemblies until you find which is causing the problem but that can be very expensive.
Dan.
Canadian "EH"
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