Battery Drain Test

WARNING: Do not attempt this test on a lead-acid battery that has recently been recharged. Explosive gases can cause personal injury.

CAUTION: To prevent damage to the meter, do not crank the engine or operate accessories that draw more than 10 amps.

NOTE: No factory equipped vehicle should have more than a 50 mA (0.050 amp) draw. Check for current drains on the battery in excess of 50 milliamps (0.050 amp) with all the electrical accessories off and the vehicle at rest for at least 40 minutes.

NOTE: Many electronic modules draw 10 mA or more continuously.

NOTE: Use an in-line ammeter between the battery positive or negative post and its respective cable.

NOTE: Typically, a drain of approximately one amp is attributed to an engine compartment lamp, glove compartment lamp, or interior lamp staying on continually. Other component failures or wiring shorts are located by selectively pulling fuses to pinpoint the location of the current drain. When the current drain is found, the meter reading will fall to an acceptable level. If the drain is still not located after checking all the fuses, it is due to the generator.

NOTE: To accurately test the drain on a battery, an in-line ammeter must be used. Use of a test lamp or voltmeter is not an accurate method due to the number of electronic modules.

Ensure junction box/fuse panels are accessible without turning on interior and hood lights.
Drive vehicle over 30 MPH to turn on and activate the vehicle systems. Park vehicle and allow to sit with ignition off for at least 40 minutes to allow electronic modules to power down.

NOTE: It is very important that continuity is not broken between the battery and the negative battery cable when connecting the meter. If this happens, the entire procedure must be repeated. Connect the battery tester between the negative battery cable and the post. The meter must be capable of reading milliamps and should have a 10-amp capability. If continuity is broken, go to step 1.

NOTE: If the meter settings need to be switched or the test leads need to be moved to another jack, the jumper wire must be reinstalled to avoid breaking continuity.

NOTE: Amperage draw will vary from vehicle to vehicle depending on the equipment package. Compare to a similar vehicle for reference.

Connect a fused (15-amp) jumper wire between the negative battery cable and the negative battery post to prevent modules from resetting and to catch capacitive drains. Disconnect the negative battery cable from the negative battery post without breaking the connection of the jumper wire.
Connect a fused (15-amp) jumper wire between negative battery cable and negative battery post. Disconnect negative battery cable from negative battery post, without breaking the jumper wire connection to prevent modules from resetting and to catch capacitive drains.
Note the amperage draw. Draw will vary from vehicle to vehicle depending on the equipment package. Compare to a similar vehicle for reference. No factory equipped vehicle should have more than a 50 mA draw (0.050 amp).
If the draw is found to be excessive, remove fuses from the Smart Junction Box (SJB) one at a time and note the current reading. Do not reinstall fuses until you have finished testing. To properly isolate each of the circuits, all of the fuses may need to be removed and install one fuse, note the amperage draw, then remove the fuse and install the next fuse, etc.
If the current draw is still excessive, remove the fuses from the Battery Junction Box (BJB) one at a time and note the current drop. Do not reinstall the fuses until you have finished testing. To properly isolate each of the circuits, all of the fuses may need to be removed and install one fuse, note the amperage draw, then remove the fuse and install the next fuse, etc. When the current level drops to an acceptable level after removing a fuse, the circuit containing the excessive draw has been located.
Check wiring diagrams for any circuits that run from the battery without passing through the BJB/SJB. If the current draw is still excessive, disconnect these circuits until the draw is found. Also disconnect the generator electrical connections if the draw can not be located. The generator may be internally shorted, causing the current drain. See WIRING DIAGRAMS .