Abs Light

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  #1  
Old 06-18-05, 05:25 PM
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Abs Light

Folks;
I have a 2002 jeep grand cherokee. This problem has come up twice in the last three weeks.When sitting at idle for a couple of minutes my battery
guage drops to nine then comes back to 14 without touching the gas pedal.
At the same time my radio starts to cut out and my odometer starts to flash.
Then my brake and abs warning light comes on and stays on.When I shut the car off the warning lights go off and the odometer stops flashing.I took the car to a shop and there dianostic machine would not come up with any malfunction code. the dianostic history showed a bad module in the brake system. When they checked the altenator it was ok but the tester read out said to replace the battery.I am confused since the jeep runs fine and the brakes work great even when the brake and abs warning lights were on.I would appreciate any suggestions since the folks at the garage are at a loss
as to what to do.Thank you in advace .
Ron
 
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  #2  
Old 06-18-05, 06:19 PM
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Sounds like an alternator to me - even if it did check good at the time.
 
  #3  
Old 06-18-05, 07:01 PM
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Are you certain it drops to 9 volts? That is excessively low. How many seconds does it stay at 9 volts?

The only time a battery drops to 9 volts is when you are cranking the starter motor for several seconds. Otherwise it should always be well above 11 volts.
 
  #4  
Old 06-19-05, 05:26 AM
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Abs Reply

FOLKS;
It only drops to 9 volts for less than a second.What I can't understand is why the engine stars to die.
Ron
 
  #5  
Old 06-19-05, 05:41 AM
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Your first post did not mention the engine attempting to die. If that accompanies each voltage drop, then the voltage drop is not the 'cause', but rather the 'effect'.

In that case I would look elsewhere for the cause. I would start with pulling codes since the problem could be anything from fouled plugs to a defective sensor.

P.S. I just read that you have pulled codes. With no codes stored, you need to note when this event happens. Does it happen only when you pull up to a stop, etc?
 
  #6  
Old 06-19-05, 06:10 AM
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Voltage drop is the cause. Engine starts to die because there isn't enough voltage to power everything. All symptoms - voltage drop, dash lights, etc. point to the alternator cutting out.
 
  #7  
Old 06-19-05, 07:56 AM
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I have an afterthought. If the voltage drops to 9 volts, which should never happen, then your battery is suspect. When your engine rpm drops below idle (as if to die), then your alternator can not put out 13 volts anymore. In this small window of time, the only voltage left to run the car is the battery, so the 9 volts that you are seeing is actually your battery voltage at that point in time. This 9 volt reading could be the sign of a bad battery.

Since the shop mentioned your battery as being weak also, it would be prudent to replace it and see if that doesn't solve the problem completely. If we mistakenly dismiss the battery as the possible cause then it could be a long painful road to diagnosis.

On the other hand, the momentary 9 volt reading may simply be a meaningless fluctuating gauge reading that occurs as the rpm drop below idle. The real problem may be an idle issue.
 
  #8  
Old 06-19-05, 11:16 AM
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Abs Light

Folks;
Today I replaced the battery.Since this is the cheapest and easiest for
me to do I'll start there.I really appreciate all the imput and will let you
know how it turns out.Thanks again
Ron
 
  #9  
Old 06-20-05, 08:01 AM
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Make sure and carry the following with you at all times: a set of jumper cables and/or tow money along with a cell phone. You have a bad alternator, and it will crap out again. May very well smoke your new battery in the process. Good luck.
 
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