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, check the vehicle for excessive parasitic current drain.

One or more on-board solid state control modules such as the PCM, may, at some time, exhibit a failure mode that causes a high parasitic drain on the vehicle's battery. When the battery is disconnected in order to install an ammeter, etc., the excessive current drain may not occur once circuit continuity is restored. Even though cycling the engine control switch key to RUN and then to OFF 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 engine control switch must not be rotated to ACCESSORY, RUN or START with an ammeter installed between the battery terminal and the battery cable, a current drain test tool must be used as described in the following procedure.

Before starting this procedure, the engine control switch must be in LOCK or OFF, all electrical accessories must be turned OFF and the doors closed.

Tools Required

NOTICE: The parasitic draw test should never be turned to the OFF position with the engine running or damage could occur to the vehicle's electrical system.

1. Disconnect the negative battery cable. Refer to

   Caution: Unless directed otherwise, the ignition and start switch must be in the OFF or LOCK position, and all electrical loads must be OFF before servicing any electrical component. Disconnect the negative battery cable to prevent an electrical spark should a tool or equipment come in contact with an exposed electrical terminal. Failure to follow these precautions may result in personal injury and/or damage to the vehicle or its components.

   in General Information.
2. Install the male end of J 38758 to the negative battery terminal.

2.1.	Remove the terminal bolt from the battery cable end of the test switch.

2.2.	Thread a terminal adapter (GM P/N 123040) onto the negative terminal post of the battery.

Important: The bottom of the adapter must make firm contact with the pad in the base of the battery.

2.3.	Put the battery cable end of J 38758 over the threaded end of the terminal adapter.

2.4.	Thread a second terminal adapter over the first adapter.

2.5.	Turn the knob of the test switch to the OFF position.

2.6.	Connect the negative battery cable to the female end of the test switch using a set of terminal adapters.

3. Turn the knob on J 38758 to the OFF position.
4. Connect the negative battery cable to the female end of J 38758 .
5. Turn the test switch to the ON position.
6. Road test the vehicle while activating all the accessories, such as the radio and the air conditioning.
7. Turn the engine control switch to OFF. Remove the key.
8. From this point on, electrical continuity must be maintained in the ground circuit to the battery, either through the J 38758 (in the ON position) or through the ammeter.

Some components, such as the PCM, 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 the next step, if a digital multimeter is being used other than the one recommended, make sure the vehicle does not have a high current drain that might damage the multimeter when it is installed. This can be done by using the following procedure.

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 and allow the current to flow through the meter.
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 in order to maintain continuity in the electrical system. Switch down to the 2 amp scale for a more accurate reading when the test switch is reopened.

12. Take the readings in milliamps.
13. Find the reserve capacity of the battery. Refer to Specifications. Divide this number by 4. Compare this to the digital multimeter reading. The current drain reading should not exceed this number.

Example: If a battery has a reserve capacity of 100 milliamps, the current drain should not exceed 25 milliamps.

NOTICE: Always turn the test switch knob to the ON position before removing each fuse in order to maintain continuity in the electrical system and to avoid damaging the digital multimeter due to accidental overloading, such as opening a door to change a fuse.

14. If the current draw is too high, remove the system fuses one at a time until the draw returns to a value less than or equal to the specifications. Start with the fuses that are "Hot At All Times."

In order to protect the meter without disrupting electrical continuity, turn the test switch ON before activating any circuits that may cause a current draw high enough to damage the multimeter. Then remove the interior lamp fuse. Note the meter reading.

If the parasitic load is still excessive, start removing other fuses one at a time. Leave the interior lamp fuse out during diagnosis so that the vehicle door can be left open.

Important: Perform the following steps each time a fuse is removed.

15. Removing the PCM 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 milliamps reading, the PCM 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, the test switch and the terminal adapters. Connect the negative battery cable to the negative battery terminal.

Tighten
Tighten the negative battery cable nut to 17 N·m (13 lb ft).

Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.