Component Tests and General Diagnostics
BATTERY - DRAIN TESTINGWARNING: 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.
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 mA (0.050 amp) with all the electrical accessories off and the vehicle at rest for at least 40 minutes. Current drains can be tested with the following procedure.
NOTE:
- Many electronic modules draw 10 mA (0.010 amp) or more continuously.
- Use an in-line ammeter between the negative battery post and its respective cable.
- Typically, a drain of approximately 1 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 falls to an acceptable level. If the drain is still not located after checking all the fuses, it is due to the generator.
- 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.
1. Make sure the junction box(es)/fuse panel(s) is accessible without turning on the interior lights or the underhood lights.
2. Drive the vehicle at least 5 minutes and over 48 km/h (30 mph) to turn on and activate 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 jumper wire (30A) between the negative battery cable and the negative battery post to prevent modules from resetting and to catch capacitive drains.
5. Disconnect the negative battery cable from the negative battery 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 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.
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 factory-equipped vehicle should have more than a 50 mA (0.050 amp) draw.
Remove the jumper wire.
8. Note the amperage draw. Draw varies from vehicle to vehicle depending on the equipment package. Compare to a similar vehicle for reference.
9. If the draw is found to be excessive, remove the fuses from the smart junction box (SJB) 1 at a time and note the current reading. Do not reinstall the fuses until you have finished testing. To correctly isolate each of the circuits, all of the fuses may need to be removed and then install 1 fuse, note the amperage draw, remove the fuse and install the next fuse. Continue this process with each fuse.
10. If the current draw is still excessive, remove the fuses from the battery junction box (BJB) 1 at a time and note the current drop. Do not reinstall the fuses until you have finished testing. To correctly isolate each of the circuits, all of the fuses may need to be removed, then install 1 fuse, note the amperage draw, remove the fuse and install the next fuse. Continue this process with each fuse. When the current level drops to an acceptable level after removing a fuse, the circuit containing the excessive draw has been located.
11. Check the wiring diagrams for any circuits that run from the battery without passing through the BJB or the 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 cannot be located. The generator may be internally shorted, causing the current drain.