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FIXITMAN
FIXITMAN, Mater Technician
Category: Pontiac
Satisfied Customers: 17142
Experience:  ASE MASTER CERTIFIED, AA DEGREE AUTO/DIESEL TECH
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The battery light on the dash comes on about 30 seconds

Customer Question

The battery light on the dash comes on about 30 seconds after starting. Battery voltage is good, alternator voltage is good, battery is charging.
Submitted: 1 year ago.
Category: Pontiac
Expert:  FIXITMAN replied 1 year ago.

Hello, my name is Bobby. Thank you for the question. Can you tell me if the battery light stays on the entire time you are driving it? What is the charging voltage as the engine is running?

Customer: replied 1 year ago.
Voltage when charging is 14.8. The alternator is new.
Customer: replied 1 year ago.
once the light comes on, it stays on.
Expert:  FIXITMAN replied 1 year ago.

Thank you. One last question. Does the voltage get higher than that when you rev the engine?

Customer: replied 1 year ago.
When revving the engine, voltage at the battery went up by .01 volts, so essentially, no it didn't change when revving.
Expert:  FIXITMAN replied 1 year ago.

Thank you. The light is turned on by the body control module depending on what the PCM is telling it. You need to see what the PCM is seeing as the charging voltage. You would need a computer scan tool that reads engine data to see what it is. If it sees what you see with the meter then chances are that the BCM is failing. If it is seeing lower voltage than what you are seeing then you have a circuit issue. Most of the time this is caused by a bad connection at the alternator, but it can also be a wiring issue.

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