# '06 Impala - lights/power pulsating (battery/alternator)



## ukrkoz (Dec 31, 2010)

you need to read codes first. 
for 06, it's prolly not alternator belt. either idle control is doing something, or one of the sensors is at fault, or simply ignition coils/spark plugs. ECM. so, read codes, it's free.


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## DIYguy2000 (Nov 4, 2009)

I have an OBD II code reader, but there is no check engine light on. Are there other codes a mechanic can read to find out what's going on? The battery light came on yesterday morning and the display said "Service electrical system", but the car was fine last night - battery light went off and no issues. This is weird.


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## DIYguy2000 (Nov 4, 2009)

It came back. No engine lights, but I checked the voltage of the battery. Unfortunately, my voltage meter is analog and doesn't have a good scale for a 12V battery (or 14V when it's running). I couldn't tell the voltage while the car was off, but could see the needle pulsating while running. However, the engine RPM's are pulsating at the same rate. It's making me think it's something to do with the engine, not the alternator anymore. Any ideas? If not, I'll be bringing it into a mechanic.

thanks!!


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## DexterII (Jul 14, 2010)

I'd remove and clean the battery cables and grounds; not sure where they would all be on that particular vehicle, but, again, based on what you desribed, I sould start there. I would also pull the battery, put it on a charger, and then have the local auto parts store load test it. Modern vehicle electronics are quite sensitive about having a correct voltage supply.


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## beamar (Apr 26, 2011)

as stated, have the battery tested. I would load test it. It might read 12 volts but fail a load test. If all is good there, I would check the voltage coming out of your alt. 


as stated, make sure your cables and the top of your battery is clean.


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## ukrkoz (Dec 31, 2010)

so i am curious. you do have a scanner. how hard is it to stick it in and read codes? not all codes throw CEL. CEL is usually emissions related codes light. i had several times when CEL will not come up, but error codes were present.


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## kadetklapp (May 4, 2011)

There might be a code stored on the computer, but without a CEL coming on, I somewhat doubt it. 

Impalas are plagued with electrical problems. Especially the police package ones. Don't even get me started on that heap. If you had the alternator tested, I suspect it could be an issue with the Body Control Module. GM's BCMs are pretty famous for being defective. When they start to crap out, the odometer, stereo, and even headlights/taillights pulsate. Could also be a faulty relay in the automatic headlight system.


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## DIYguy2000 (Nov 4, 2009)

Had CAA test the battery for me (while it was still in the vehicle) 3 weeks ago. Here are the results:

Battery Test
_Good Battery_
Voltage: 12.45V
Measured: 544 CCA
Rated: 600 CCA
Temp: 13C

Starter Test
_Cranking Normal_
Voltage: 11.00V
Amps: 47.6A
Time: 1.84s

Charging System Test
_No Problems_
No Load: 13.88V, 0.1A
Loaded: 13.85V, 0.6A
Ripple: 41mV

Drain Test
_Pass_
0.36A


I was told there was nothing wrong, but that I should place the battery on a charger at a low amperage. I charged it for a few hours at 2A until the charger stated it was 100% full. No problems after that.

The car was not used over the weekend, and it was raining. This morning I had the same issues with pulsating lights, and pulsating loss of power (especially noticeable while slowing down/braking at low speeds, and while climbing hills at moderate speeds.) Pulsating is at about 100 to 110 per minute at idle, and about 150 to 160 per minute at 4000RPM (not that the engine operates that high during my morning commute - I just wanted to see if the pulsating changed at higher RPMs).

I haven't tried cleaning the terminals yet. Can someone provide the steps (which cable off first / on last, what to use while cleaning, etc).

I'll also try the code reader, but I'm pretty sure there aren't any codes to read as I've tried plugging it in before without a CEL. It's just a cheap reader, no options like the nice big garage OBDII readers/computers.

Any other ideas out there?

Thanks!


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## Bigplanz (Apr 10, 2009)

Since rain (moisture) affects this condition and it is affecting the ignition system (engine surge/unstable idle) and the lights/accessories, I am going to guess a bad ground somewhere. Check the ground wire on the engine block, and other system grounds for good contact. See if you can find a detailed electrical schematic to find the grounds. Most (all?) GM ground wires are black, so that might help you. Then check any relay box/junction where all these components might share a ground. 

Note: WAG (wild ass guess) on my part, as I haven't worked on a car less than 10 years old in about five years. 

Oh, the negative battery cable always comes off first.


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## DIYguy2000 (Nov 4, 2009)

Cleaned all the connections a few weeks ago and still haven't had an issue yet. Fingers crossed.


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