Battery Electrical Drain

If the vehicle exhibits a low or dead battery after an overnight period, or discharges over a period of 2 or 3 days, the electrical system should be checked for an excessive electrical drain. This is referred to as "parasitic current drain." If a battery needs recharging and no cause is evident, refer to "Battery Testing". One or more on-board solid state control modules, such as the PCM or VCM, may, at some time, exhibit a failure mode that causes a high parasitic drain on the vehicle's battery.

When the battery is disconnected to install an ammeter, the excessive current drain may not occur once circuit continuity is restored. Even though cycling the ignition key to the "RUN" and then to the "OFF" position may at times cause such a drain to recur, there may be drains that will not recur unless the vehicle systems are reactivated in a road test. Since the ignition switch must not be rotated to the "ACCESSORY," "RUN," or "START" position with an ammeter installed between the battery terminal and the battery cable, refer to "Current Drain Test".Current Drain Testing