Battery Light/Service engine soon light
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Old February 2nd, 2011, 02:52 PM   2 links from elsewhere to this Post. Click to view. #1
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Battery Light/Service engine soon light


Yesterday, I sat in an assload of traffic going to and from Disneyland.

On the way home after sitting in a bit of traffic my battery light came on, flickered, went out, came back on, flickered on and off and then stayed off.

Then about 15 minutes later my Service engine soon light came on. ( and is still on)

Pulling into my drive way this morning after a grocery run, The battery light is now on solid, along with my Service engine light.

Is is possible these two things are related?

I have a scanner but I can't scan my car until tonight.
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Old February 2nd, 2011, 03:38 PM   #2
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10 to 1 bad alternator.
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Old February 2nd, 2011, 03:49 PM   #3
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would a bad alternator cause the service engine soon light to come on though? for some reason I thought the check engine light only came on if a sensor was going bad or misreading.
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Old February 2nd, 2011, 03:55 PM   #4
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im going to guess alternator also
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Old February 2nd, 2011, 04:36 PM   #5
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Originally Posted by Genevieve View Post
would a bad alternator cause the service engine soon light to come on though? for some reason I thought the check engine light only came on if a sensor was going bad or misreading.
Simple answer: Yes

Went through two alternators when I first bought my mustang and you have described the symptoms of a failed alternator just hope it hasn’t been going on long enough to fudge your battery. Very simple head over to autozone if you have them in your area have them test. Aright its bad now swap it out in the parking lot so you can get your core charge back plus they can charge up your battery while you work on your car. Hey...that’s what I did (-:
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Old February 2nd, 2011, 05:46 PM   #6
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I don't believe in the 'load' test AZ does can truly detect a bad alternator. They hook it up while it's in the car, at that point you're load testing the battery (unless the battery is toast also). - I could be wrong though - but every time I've had a bad alternator, they would test it, and say it's good - as the battery was good at the time. The best way is to remove the alternator, and have it bench tested.

Honestly though,,,removing the alty takes all of 5 mins, so just swap it out. I'm about to go get my 2nd AZ reman alty - the one I got a couple months ago pops my battery light every day for a few miles till it warms up.
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Old February 2nd, 2011, 06:06 PM   #7
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Originally Posted by Genevieve View Post
would a bad alternator cause the service engine soon light to come on though? for some reason I thought the check engine light only came on if a sensor was going bad or misreading.
When the battery voltage is low (below 10.5V officially however anything below 11.0V is bad) many sensors will start to return values that are out of acceptable bounds--this can trigger power train related (Pxxx) DTCs.
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Old February 2nd, 2011, 07:32 PM   #8
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Originally Posted by cliffyk View Post
When the battery voltage is low (below 10.5V officially however anything below 11.0V is bad) many sensors will start to return values that are out of acceptable bounds--this can trigger power train related (Pxxx) DTCs.

ahhh, That totally makes sense. Thanks
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Old February 3rd, 2011, 11:42 AM   #9
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The only code the reader came up with was "Insufficient Coolant Temperature for Closed Loop Fuel Control"
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Old February 12th, 2011, 04:04 AM   #10
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i had a question about this.
i had installed a new alternator and new battery and the battery light comes on once the car is started and goes off after acouple of miles driving it.
what can be the cause of this? my grandpa tells me its the terminals cause they look old.

if anyone knows how i can solve this problem please let me know
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Old February 12th, 2011, 08:58 AM   #11
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Listen to your grandfather and check that the battery terminals are solid. Also check the ground connection to the block, just behind the oil filter adapter--that connection is know to get corroded and/or loose as these cars age...
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Old February 12th, 2011, 09:37 AM   #12
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ok. will do. the terminals have small type holes on them. the part that goes on the battery post. the terminals are still tight though.

and the ground connection is under the car behind the oil filter? am i looking for a wire connected to the car with a bolt?
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Old February 12th, 2011, 09:55 AM   #13
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Originally Posted by rangel515 View Post
ok. will do. the terminals have small type holes on them. the part that goes on the battery post. the terminals are still tight though.
Are they the stock terminal connectors?

One thing you can do is measure the voltage between the negative battery post (the actual lead post) and the negative connector body, while someone is starting the engine. This will check the voltage drop between the battery post and the connector--it should be 0.0V or very close to it.

Next check the voltage between the battery terminal and the block, again while starting the engine--ideally this should also be 0.0V however it may be as high as 0.5V and still be OK. Anything higher than 1.0V means there is too much resistance in the "ground" connections between the battery and the block; the generator is grounded to the block.

Also, what year is your car?

and the ground connection is under the car behind the oil filter? am i looking for a wire connected to the car with a bolt?
Yes, it is a rather substantial wire, same size as the wires at the battery. To clarify I should have said "to the rear of", not "behind" the oil filter.
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Old February 12th, 2011, 10:13 AM   #14
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2002 v6
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Old February 12th, 2011, 11:04 AM   #15
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Originally Posted by rangel515 View Post
2002 v6

I am not familiar with the V6, not sure if the same engine grounding point is used, however there will be one, and the voltage measurements described above hold true for any car.
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Old March 11th, 2011, 10:51 PM   #16
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The Battery light is STILL coming on, even after I put a new alternator on.

whhhyyy!?!

I'm so mad about this, I just spent almost 220 dollars on a new alternator and a new belt... and it didn't even fix my problem!



Oh I just saw the post about the grounding to the block, I will check that out soon.
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Old March 11th, 2011, 11:06 PM   #17
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Check the wires on the connector going into the alternator, sometimes your alternator will be charging fine and the connector will be bad and can cause your batt light to come on when everything is fine. So if you can, have a friend watch your instrument cluster while you wiggle the connector on the alt to see if the light flickers any and check your alt output with a dmm to see what it's output is
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Old March 11th, 2011, 11:13 PM   #18
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Originally Posted by yzdirtbikes144 View Post
Check the wires on the connector going into the alternator, sometimes your alternator will be charging fine and the connector will be bad and can cause your batt light to come on when everything is fine. So if you can, have a friend watch your instrument cluster while you wiggle the connector on the alt to see if the light flickers any and check your alt output with a dmm to see what it's output is
I will try that.

It stayed off after I changed my alternator, Until I was driving out to my dads house and I passed a car on a two lane road, dropped it into 3rd and hit 90mph and my light came on, and stayed on.
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Old March 12th, 2011, 12:18 AM   #19
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It's also not unheard of to get a bad alt from the parts house. I had a navigator at work one day I put a total of 3 alternators on before we finally got a good one. Frustrating as hell and will have you scratching your head, second guessing your diagnoses and running pinpoint tests over something as simple as the charging system. Be sure you check the output with a multimeter, if it's putting out less than 12.0volts(ideally around 13-14.0v, once you start getting around 15v it's starting to get close to overcharging)with all your accessories turned(so there's a decent load on it) I'd take it back to your parts place and have them warranty it
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Old March 12th, 2011, 12:34 AM   #20
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Thanks, I was thinking there was a possibility I got a bad alternator, Ill have to check it out tomorrow sometime.
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