Component Tests and General Diagnostics
COMPONENT TESTS12 Volt Battery - Drain Test
WARNING: Do not attempt this test on a lead-acid battery that has recently been recharged. Explosive gases may cause personal injury. Failure to follow these instructions may result in personal injury.
CAUTION:
- To prevent damage to the meter, do not crank the engine or operate accessories that draw more than 10A.
- If equipped with the CD6 audio unit, precautions must be taken when the battery has been disconnected. When reconnecting the battery, make sure no interruption of power occurs for 30 seconds. If power is interrupted during the first 30 seconds, permanent damage to the CD6 audio unit will result.
NOTE:
- No production vehicle should have more than a 50 milliamp (mA) or 0.050 amp draw with the key in the OFF position.
- The 12 Volt Battery - Drain Test can not be carried out while the jump start procedure for the high voltage battery is being carried out. Drain testing of the low voltage battery during a jump start procedure may result in a failed 12 Volt Battery - Drain Test.
- Many modules draw 10 mA (0.010 amp) or more continuously.
- Use an in-line ammeter between the battery positive or negative post and its respective cable.
- Typically, a drain of approximately 1 amp can be attributed to an engine compartment lamp, glove compartment lamp, or interior lamp staying on continually. Other component failures or wiring shorts may be located by selectively pulling fuses to pinpoint the location of the current drain. When the current drain is found, the meter reading falls to an acceptable level. If the drain is still not located after checking all the fuses, it may be due to the generator.
- To accurately test the drain on a battery, an in-line digital ammeter must be used. Use of a test lamp or voltmeter is not an accurate method due to the number of electronic modules.
Check for current drains on the battery in excess of 50 milliamps (mA) (0.050 amp) with all the electrical accessories off and the vehicle at rest. Current drains can be tested with the following procedure:
1. Make sure the battery junction box (BJB) and the smart junction box (SJB) are accessible without turning on interior and underhood lights.
2. Drive the vehicle at least 5 minutes and over 48 km/h (30 mph) to turn on and exercise the vehicle systems.
3. Allow the vehicle to sit with the key OFF for at least 40 minutes to allow the modules to time out/power down.
4. Connect a fused (10A) jumper wire between the negative battery cable and the negative battery post to prevent the modules from resetting and to catch capacitive drains.
5. Disconnect the negative battery cable from the post without breaking the connection of the jumper wire.
6. 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 tester between the negative battery cable and the post. The meter must be capable of reading milliamps and should have a 10 amp capability.
7. 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.
- Amperage draw varies from vehicle to vehicle depending on the equipment package. Compare to a similar vehicle for reference.
- No production vehicle should have more than a 50 mA (0.050 amp) draw.
Remove the jumper wire.
8. If the draw is found to be excessive, pull the fuses from the BJB/SJB one at a time and note the current drop. Do not reinstall the fuses until you are finished testing.
9. Check the wiring schematic in the wiring diagram for any circuits that run from the battery without passing through the junction boxes. Disconnect these circuits if the draw is still excessive.
12 Volt Battery - Electronic Drains Which Shut Off When the Battery Cable is Disconnected Test
1. Repeat the steps of the 12 Volt Battery - Drain Test.
2. Make sure all doors are closed and accessories are off. Without starting the engine, turn the key to ON for a moment and then OFF. Wait a few minutes for the illuminated entry lamps to turn off, if equipped.
3. Connect the ammeter and read the amperage draw.
The current reading (current drain) should be less than 50 mA (0.050 amp). If the current drain exceeds 50 mA (0.050 amp) after a few minutes, and if this drain did not show in previous tests, the drain is most likely caused by an inoperative electronic component. As in previous tests, remove the fuses from the BJB and the SJB one at a time to locate the problem circuit.