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Roy
Roy, import/domestic specialest
Category: Chevy
Satisfied Customers: 5126
Experience:  ASE master tech for 40 years
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I am trying to diagnose a parasitic amp draw on my 2007

Customer Question

Customer: Hello, my name is ***** ***** I am trying to diagnose a parasitic amp draw on my 2007 Chevy Impala and I have narrowed it down to 2 fuses, the display fuse as well as the radio fuse. with neither installed the draw is .20-.22 with display .56-1.27 and with the radio as well it is 1.3-2.24 and radio only its 1.1-1.46.
JA: Thanks. Can you give me any more details about your issue?
Customer: The battery dies when the car sits. and when i try to start the car sometimes the locks and display flash and its a weak start.
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Submitted: 1 year ago.
Category: Chevy
Expert:  Roy replied 1 year ago.

good afternoon my name is ***** ***** I will assist

the numbers you gave us, are they amps or milli amps??

Roy

Customer: replied 1 year ago.
good question, I can tell you how my voltage meter is set up if that helps: I have the positive lead on the unfused 20a max port and the setting on the 20 in the A--[a long dash with 3 short dashes under it.]
Expert:  Roy replied 1 year ago.

ok, first, use the amp portion of the meter. use a scale around 3 amps. you are looking to have only 50-75 milli amps as a draw.

once you insert the meter in line, let it rest for 5 minutes so the modules can go to sleep and then look at the draw.

Roy

Customer: replied 1 year ago.
https://www.youtube.com/watch?v=bUHRsP7xEt4&index=1&list=UUAlAXHUhcL_97AdkHBlSh3Q video of the test
Customer: replied 1 year ago.
here is an image of how the meter was set
Expert:  Roy replied 1 year ago.

nice meter

your red lead is in the wrong slot. move it over to the ma slot and your black in the ground. then you have it set right

Roy

Customer: replied 1 year ago.
for clarification, the red to the 2nd slot(ma) and the black needs to be moved to where? and should I continue the test by disconnecting the negative lead to the battery and completing the loop with the meter?
Expert:  Roy replied 1 year ago.

yes to the red. the black is fine where it is. yes, the negative cable off with the meter in line

Roy

Customer: replied 1 year ago.
i get no reading at all with the red lead in the ma slot, only in the unfused slot to its left?
Expert:  Roy replied 1 year ago.

check the fuse in the meter to be sure it is good. it is inside the back case.

you can use the other port but there is no protection to your meter from a voltage spike

Roy

Customer: replied 1 year ago.
ok, the meter aside can you not tell me what could be causing the draw based on the numbers i have shown or the video I sent you? knowing that there is a draw from both the radio and the display?
Expert:  Roy replied 1 year ago.

the draw from the radio is most likely the culprit. the display is a module and most likely will cease to pull current after it goes to sleep.

you still have not told me if the numbers were amps or milli amps??

Roy

Customer: replied 1 year ago.
I believe to the best of my understanding that it is amps. I also believe that it is a combination of both the radio and the display because I had the radio fuse out for months and still had issues with draw.
Expert:  Roy replied 1 year ago.

ok, thats new information not provided.

have you tried putting the radio fuse back and leaving out the display fuse??

the common denominator here is the bcm. try unplugging the bcm and see if the draw goes away.

Roy

Customer: replied 1 year ago.
the radio fuse seems to have an even larger draw on the car then the display fuse looking at the meter numbers. could the bcm effect both the radio and the display draws?
Expert:  Roy replied 1 year ago.

yes, the bcm controls all body functions. both items are controlled by the bcm

Roy

Customer: replied 1 year ago.
I removed the bcm and will have to wait until tomorrow to get a replacement and test to see if there is still a draw. Thank you for your help I will be in touch tomorrow.
Expert:  Roy replied 1 year ago.

thanks.

please dont forget to rate me as it is the only way I get paid for my efforts

Roy

Customer: replied 1 year ago.
with the bcm removed and both fuses reinstalled over night the battery was 12.83v when I left it and is now 12.1v this means there is still a draw right? Picking up the bcm today.
Expert:  Roy replied 1 year ago.

.6 volts overnight??? not really. there will always be a small draw to keep some modules alive.

thats why 50-75 milli amps is normal. it is a draw

Roy

Expert:  Roy replied 1 year ago.

how are you making out

Customer: replied 1 year ago.
Just waiting on the part to come in, I'll get back too you as soon as I can.
Expert:  Roy replied 1 year ago.

ok

Customer: replied 1 year ago.
Is there anything that needs to reset or reason why the car wouldn't start with the new bcm?
Expert:  Roy replied 1 year ago.

did you have it flashed to your car???

Roy

Customer: replied 1 year ago.
I will soon, thank you for letting me know that was necessary.
Expert:  Roy replied 1 year ago.

ok.

please dont forget to rate me as it is the only way I get paid for my efforts

Roy