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If the battery is weak, voltage drops below very specific thresholds and cause some vehicle networks like CAN and LIN to shut down and the connected module to set codes that indicate a loss of communications.
This can occur during extended cranking cycles of when the electrical system is under high loads. Andrew Markel looks at how a vehicle and voltages below 7- and 12-volts can set codes. This video is sponsored by Auto Value and Bumper to Bumper.