Parasitic Draw Test
BATTERY ELECTRICAL DRAIN / PARASITIC DRAW TESTParasitic Draw Test:
NOTE: Always check Technical Service Bulletins for any revised procedures or specifications.
TOOLS REQUIRED:
J 39200 Digital Multi meter
J 38758 Parasitic Draw Test Switch
NOTICE: The parasitic draw test switch should never be turned to the "OFF" position with the engine running or damage could occur to the vehicle electrical system.
1. Remove the negative battery cable at the battery.
2. Install the J 38758 male end to the battery negative terminal.
3. Turn the knob on the test switch to the "OFF" position.
4. Install the negative battery cable to the female end of the test switch.
5. Turn the test switch to the "ON" position.
6. Road test the vehicle while activate all of the accessories (radio, A/C, etc.).
7. Turn the ignition switch to the "OFF" position and remove the key.
IMPORTANT
^ From this point on, electrical continuity must be maintained in the ground circuit to the battery, either through J 38758 (in the "ON" position) or through the ammeter.
8. Some components, such as PCM's, have timers that draw several amps of current while they cycle down. This can give a false parasitic drain reading. Wait 15 minutes for these components to power down before continuing this test.
IMPORTANT
^ Before performing step 9, if a multimeter is being used other than J 39200, make sure the vehicle does not have a high current drain that might damage the multimeter when it is installed. This can be done useing the following procedure:
^ Connect a jumper wire with an in-line 10-amp fuse to the terminals on the drain test switch. Then turn the test switch to the "OFF" position. Wait about 10 seconds. If the fuse does not blow, current draw is less than 10 amps, and the multimeter can be used safely. Before removing the fused jumper wire and installing the multimeter, turn the test switch to the "ON" position.
9. Set J 39200 to the 10-amp scale and connect it to the terminals on the test switch.
10. Turn the test switch to the "OFF" position to allow current to flow through J 39200.
11. Wait at least 60 seconds. Check the current reading. If the current reading is at or below 2 amps, turn the test switch to the"ON"position (to maintain continuity in the electrical system) and switch down to the 2 amp scale for a more accurate reading when the test switch is reopened.
12. Take the reading in milliamps.
13. Find the reserve capacity of the battery in "specifications". Divide this number by 4. Compare this to the J 39200 reading. The current drain reading should not exceed this number. (Example: if a battery has a reserve capacity of 100 minutes, the current drain should not exceed 25 milliamps).
NOTE: Always turn the parasitic draw test switch knob to the "ON" position before removing each fuse to maintain continuity in the electrical system and to avoid damaging the ammeter due to accidental overloading (I.E. opening door to change fuse etc.).
14. If current draw is too high, remove system fuses one at a time until the draw returns to a value less than or equal to the specification. Start with fuses that are hot at all times. To remove the fuse, you must first open the door. This may cause a high enough current draw to damage the multimeter. To protect the meter without disrupting electrical continuity, turn the test tool to the "ON" position before opening the door. Then remove the courtesy lamp fuse. Note the meter reading. If the parasitic load is still excessive, start removing the other fuses, one at a time. Leave the courtesy lamp fuse out during diagnosis so the vehicle door can be left open. Perform steps 10 through 12 each time a fuse is removed.
15. Removing the PCM or VCM fuse should cause a drop of less than 10 milliamps.
^ If the drop is more than 10 milliamps, check the orange wires for a short to ground. Also check the components connected to the orange wires.
^ If there is no drop in the milliamp reading, the PCM or VCM is not drawing current.
16. Repeat the parasitic current drain procedure after any repair has been completed.
17. When the cause of excessive current draw has been located and repaired, remove the meter, test switch, and terminal adapters and connect the negative battery cable to the negative battery terminal.