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Discussion Starter #1
While driving home last night a bizarre set of circumstances began to unfold with my 1999 S70 T5. The first thing I noticed was that my dash lights and headlights pulsed when I tapped the brakes. After a few miles the ABS and Check Engine lights came on. Then as I was exiting the freeway, the headlights began to intermittently turn off for a brief moment every minute or two. I’m thinking that this might be the ABS module, but would welcome any other thoughts.
 

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Sounds like the ABS module is freaking out, sucking all the voltage trying to eliminate a slipping wheel that isn't there!

It needs to be popped open and resoldered...or sent off to a rebuilder. Lots of info about these ABS modules out there.
 

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If your electrical system is running at full strength, the ABS operation, whether it should be
pulsing or not at that point, should not affect your dash and headlights. Sounds like low voltage.
Low voltage can cause all manner of strange electrical things to happen. And ABS is electrical.
I'd check out your charging system and it's voltage levels before making any assumptions.
Could be something as simple as neglected battery cables and connections, bad battery, etc.
 

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That's true, always check your power source first. My lights would always dim a bit when the ABS functioned (properly in the snow) but would never turn off.
 

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Discussion Starter #5
It seems that it was something that simple. Uncovered the battery terminals and they were very fouled. Cleaning the terminals and cables seems to have resolved the issue - I hope. Thanks!!!
 

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If your battery cables have never been replaced you may be due. Pay particular attention to the "B positive" cable that runs from the battery, under the airbox, to your fuse/relay box. Open your fuse box and look at the red cables coming into it at the bolt, you may notice that it is burnt or corodded there. Also, check the battery cable that goes to the starter, especially at the battery terminal, it could be corodding where the cable is crimped into the terminal.
 

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Sounds like the ABS module is freaking out, sucking all the voltage trying to eliminate a slipping wheel that isn't there!
Huh? I LOL'ed

If your battery cables have never been replaced you may be due. Pay particular attention to the "B positive" cable that runs from the battery, under the airbox, to your fuse box. Open your fuse box and look at the red cables coming into it at the bolt, you may notice that it is burnt or corodded there. Also, check the battery cable that goes to the starter, especially at the battery terminal, it could be corodding where the cable is crimped into the terminal.
This ^
 

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When the pump runs, it sucks some juice and a little dimming is normal. If you have a faulty speed sensor reading, or a bad module, it can run and think a wheel is slipping when in reality none are.
 

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Yeah, it draws power, but if it's to the point of the CEL and headlights turning off, you got other issues. :)
 
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