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littlefish

abs pump running continuously - key off

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took the wife's 95 legacy wagon for gas in the snow yesterday, and gave the abs a couple of innocent little tests. after gassing, i heard a motor noise with the key off. upomn landing in the garage and lifting the hood, and noticing the ABS light on the dash, found the abs "pump" running with the key off. i am referring to the steel billet-looking box with the maze of brakelines spewing forth and the mysterious black box glued to the side. pulling batt neg reset it, and a short ride around the block showed abs working again, no idiot light. any ideas? the car had a full brake job about a thousand miles ago or less - no problems... maybe just some ice in a sensor?

 

thanks!

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Originally posted by littlefish

took the wife's 95 legacy wagon for gas in the snow yesterday, and gave the abs a couple of innocent little tests. after gassing, i heard a motor noise with the key off. upomn landing in the garage and lifting the hood, and noticing the ABS light on the dash, found the abs "pump" running with the key off. i am referring to the steel billet-looking box with the maze of brakelines spewing forth and the mysterious black box glued to the side. pulling batt neg reset it, and a short ride around the block showed abs working again, no idiot light. any ideas? the car had a full brake job about a thousand miles ago or less - no problems... maybe just some ice in a sensor?

 

thanks!

 

Ice buildup will not likely cause this, nor will a bad sensor. It is a pump or wiring issue.

 

The Bosch ABS pump is known to do this on occasion, and the only solution is to replace it.

 

We'll cross our fingers that this was a freak occurence. If it happens again I would pull the ABS fuse out to prevent further damage to the system. With the fuse out your brakes will still work, but without ABS function.

 

I would test your ABS on a slippery road and see if the pump works correctly and then shuts down once the car stops. If it stays running after the vehicle stops the pump relay is sticking and you likely need a new pump.

 

The pump is directly connected to the battery system, it is not connected to the key, which is why the pump ran with your key out. When ABS function is needed the brake control module will activate the pump and trigger the required valves to release and reapply each individual brake. The control module is only powered up when the key is in the "On" position, which is why this problem is probably isolated to the pump, or its wiring.

 

The ABS system will display codes to indicate a pump problem, sensor problem, etc. You should have these codes read the next time this occurs.

 

Another big thing to check is the brake fluid level, and to check to see if there is any air trapped in the brake system. Sometimes a brake job will force air or dirt back into the ABS pump causing problems. I would do a brake bleed to eliminate air in the brake lines as a possibility.

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thanks, alias... it happened again today. she was able to shut the engine off, start again, and it cleared. the car had a brake job recently, so we will ask the dealer to bleed it again...

just so i have it straight, if i pull the abs fuse, the system won't activate, so no chance of the pump running on. normal brakes from then on... i'll post results after we see the dealer.

:-\

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FWIW there's a TSB about a sticking ABS motor relay, it says to replace the relay with an updated part if it's bad.

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Originally posted by avk

FWIW there's a TSB about a sticking ABS motor relay, it says to replace the relay with an updated part if it's bad.

 

And since its safety related the fix should be free even though TSB's are normally only paid for during the warranty period. Argue this point with the dealer if they refuse to cover it.

 

Some TSB's such as this one should have been a recall.

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thanks - the relay was replaced for $150... is that the relay in the box inside the left front fender? wifey is going to research this and talk to the dealer.

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It's one of the two relays under the cover next to the ABS hydro unit. Even from a dealer it shouldn't be more than $50, and the labor is just to pull the old one out and plug the new one in.

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My wife's 94 Legacy had the same thing happen many years ago. The only way to get it to stop was to remove a battery cable. The dealer replaced the ABS relay under warranty. Haven't had a problem in 100K+ miles since.

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