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service brake booster

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Join Date: Dec 2009
Posts: 4

December 5th, 2012, 3:36 PM   #1  
service brake booster

2003 avalanche 170K on odometer getting service brake booster on Instrument cluster where the odometer reading should be. This only started after the alternator failed. Replaced alt got rid of that not charging message but can't get rid of the service brake booster message. I have replaced the aux vacuum pump attached to the brake booster. Still getting message but only comes up after you touch the brakes the first time after a restart. Had instrument cluster repaired in Aug but message didn't come up until alt failure at thanksgiving. Any ideas on how to trouble shoot this / fix this.

Problem fixed this is an FYI the new alternator wasn't right it would charge the vehicle fine but it wasn't producing 12 volts on the p pin (dark blue wire) of the plug on the top of the alt. the supplemental brake assist pump has to have that 12 volts in order to operate. It is what tells the pump that the engine is running. Put another alt on. The 12 volts was on that pin and the message has not come back. That line goes directly to the SBA pump no where else. and on most vehicles it is not used.

Last edited by wtroger; December 13th, 2012 at 10:26 AM. Reason: problem fixed
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