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Chevy expert
Chevy expert, ASE Certified Technician
Category: Chevy
Satisfied Customers: 10370
Experience:  30 yrs experience ase cetified tech shop owner
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Replace both batteries on 2008 duramax 6.

Customer Question

replace both batteries on 2008 duramax 6.6 litre
Submitted: 5 years ago.
Category: Chevy
Expert:  Chevy expert replied 5 years ago.
Welcome to just I'm here to help you and your 100% satisfaction is my goal.This can be caused by a few things does the security light remain on while trying to crank? Using a scan tool see it there are any trouble codes stored in the memory ?There is also a a reprogramming available to cure this problem ocassionally the pcm will need to be replaced Confirm there are no codes in the theft deterrent module. Install the latest Engine Control Module calibration per Customer Satisfaction
Expert:  Chevy expert replied 5 years ago.

If the security light is remaining on we will do a reset procedure

Complete a relearn procedure on the Passlock VTD security system. Verify that the battery is fully charged. Use a scan tool to clear any DTCs. Remove the scan tool. Turn the ignition switch to the CRANK position for about one second, then release to the ON position. Leave the ignition in the ON position for 10-14 minutes. Do not go under 10 minutes or the relearn will abort. After the 10-14 minute cycle, turn the key off for 15 seconds. This will power the vehicle down. Repeat steps 4, 5 and 6 as written two more times 3 times total After the 3rd cycle, the theft system should synchronize to the new Passlock sensor. It should then start and run normally

Customer: replied 5 years ago.
charged driver side battery . not holding charge
Customer: replied 5 years ago.
Relist: Incomplete answer.
Expert:  Dr.Automotive replied 5 years ago.
Hello and welcome to Justanswer. My name is Danny I am a Automotive Mechanic here to help you with your problem.

How can I help you with the problem your having?

If the battery is not charging you need to check the alternator as the most likely cause.

If the battery itself will not take a charge from the alternator than you could have a faulty replacement battery or incorrect battery cables routing.
Expert:  Chevy expert replied 5 years ago.

Please clarify for me a little bit if the batteries are fully charged does the engine crank and start ?If you have something draining the battery's We need to determine what that is if only one batteries going dead Make sure that you do not have a defective battery that you just purchased ,

With the engine running make sure that you have 13.8 or 14 volts across the battery terminal of both battery's . With the engine turned off you would expect approximately 12 volts across the battery terminals checked both sides .

Now something is draining both battery's will need to find that inside the truck very commonly the battery's will train because of a faulty body control module .

Now the body control module is located under the left side of the dash , If you unplug the body control module tell me if the battery still draining go dead . If you have in amp meter we can actually checked the current draw on the batteries and tell when we eliminate The component that is draining them Just let me know what you find and we will continue testing further ,Thank you