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Discussion Starter #1
Hi folks,
I have a 2008 FJ that is pretty much stock. Over the weekend I had a dead battery, so replaced the battery.
But when It started, the Brake alarm is on along with the ABS and trac lights. The brake pedal had no pressure at all so I had it towed to my mechanic.
He said the ABS unit had gone bad, and i could replace it for about 2,000 with a new master cylinder or replace the whole system with new accumulator and something else ( i forget what) for 3,000.
Anyone else ever run into this or heard of this happening? There were no other issues before this battery replacement.
 

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The initial thought might be "no way that a a dead battery can kill the ABS pump", but could a failure in the ABS pump control electronics allow the pump to run continuously for hours, thereby killing the pump and draining the battery?

Or during the time the battery was "dead", some attempt was made to jump start the vehicle with the jumper cables mis-connected?.

So additional information would be helpful:
1. How many total miles on the vehicle?
2. Is the battery an AGM, or conventional wet-cell?
3. How old is the battery?
4. Did the electrical system give any indications of battery or alternator problems in the weeks or days before the battery "died"?

Now here are the "real" questions
5. Was any attempt made to jump-start the vehicle before the battery was replaced? (With the risk that the jumper cables were incorrectly connected, even for a tiny fraction of a second?)
6. During installation of the new battery, is there any chance that the battery was mis-connected (reversed polarity), even for just a tiny fraction of a second?
 

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Discussion Starter #3
1. How many total miles on the vehicle? 112k
2. Is the battery an AGM, or conventional wet-cell? standard wet-cell
3. How old is the battery? I bought the truck in 2014 and this was the first time i replaced it
4. Did the electrical system give any indications of battery or alternator problems in the weeks or days before the battery "died"? No i had no other issues

I did try to jump the battery , but it was very dark and it was like 2 am and it was in the woods, so its possible i crossed the wires.
I got a ride and just came back the next day with a fresh battery. Cranked right up with the new battery but then the brake issue started.
 

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OK, I think we are getting closer to understanding what may have happened to the brake booster.

"I did try to jump the battery , but it was very dark and it was like 2 am and it was in the woods, so its possible i crossed the wires."

So the attempt at jump starting was unsuccessful? Please state EXACTLY what happened during and after the point when the jumper cables were connected.

There may still be a chance that the booster survived; check the 40A ABS motor fuse, and the 30A ABS solenoid fuse.
 

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Discussion Starter #5
I dont have the truck, its still at the garage so i cant check the fuses

After I hooked up the cables, I cranked the key and nothing, not even the starter motor.
that was It so i left and came back with the new battery.

If I could find the right part, im ok with replacing it myself.
 
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