Battery Electrical Drain / Parasitic Load Test - keywords 8 ab astra aura dead drain draw drop electrical gmt201 gmt960 gmx001 gmx002 ion outlook pic4790 pic4790a pic4798 resistor saturn voltage vue

This PI was superceded to add keywords GMT201, GMT960 and change the PI number referenced for class-2 diagnosis to PIC4798 from PIC3589C. Please discard PIC4790.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

When performing a parasitic load test using the Saturn special tool SA9130Z, it is possible that the voltage drop induced by the resistor in the tool can cause the modules on the vehicle not to go into low power mode properly. This can cause an erratic parasitic load reading, and may cause inaccurate diagnosis of the electrical drain.

When performing battery drain diagnostics, the current draw can be measured directly, which prevents the possibility of a voltage drop causing modules to shut down and wake back up. One way of measuring the circuit directly is by the use of parasitic draw test switch tool J38758 and DVOM J39200 with the procedure below.

1. Disconnect the battery negative cable from the battery negative terminal. Refer to Battery Negative Cable Disconnection and Connection.
2. Install the male end of the J 38758 to the battery ground terminal.
3. Turn the J 38758 test switch to the OFF position.
4. Install the battery negative cable to the female end of the J 38758.
5. Turn the J 38758 test switch to the ON position.
6. Road test the vehicle and activate ALL of the accessories, including the radio and air conditioning. This may take up to 30 minutes.
7. Park the vehicle. Turn the ignition switch to the OFF position and remove the ignition switch key.
8. Connect a 10 A fused jumper wire to the test switch tool terminals.
9. Turn the J 38758 test switch to the OFF position. The current now flows through the jumper wire.
10. Wait 1 minute. If the fuse blows, install an inductive ammeter to locate the current draw.
11. Turn the test switch to ON and then remove the fused jumper wire.
12. Set a digital multimeter to the 10 A scale.
13. Connect the digital multimeter to the test switch tool terminals.
14. Turn the J 38758 test switch to the OFF position. The current flows now through the digital multimeter.
15. Wait 1 minute. Check and record the current reading.

*When there is a current reading of 2 A or less, turn the J 38758 test switch to the ON position. The electrical current will now pass through the switch.

*Then switch the digital multimeter down to the 2 A scale for a more accurate reading when the J 38758 test switch is turned OFF.

16. Turn the J 38758 test switch to the OFF position. Wait up to 45 minutes for most vehicles.
17. Check and record the current reading.
18. Note the battery reserve capacity, amp hour rating. Refer to Battery Usage.

*Divide the reserve capacity by 4, amp hour rating by 2.4.

*Compare this to the multimeter milliampere reading taken in the previous step. The parasitic current drain should not exceed this number. Example: If a battery has a reserve capacity of 100 minutes, (60 A/H) the current drain should not exceed 25 mA.

19. If excessive current drain is not found at this time and there are no other apparent causes, complete the following:

*Using the MIN/MAX function of the digital multimeter, monitor the parasitic drain overnight or during the day. This will determine if something has been activated during that time frame.

Notice: The test switch must be in the ON position when removing the fuses in order to maintain continuity in the electrical system. This avoids damaging the digital multimeter due to accidental overloading, such as a door being opened to change a fuse.

Important: Removing fuses, relays, and connectors to determine the failure area may wake up modules. You must wait for these modules to go to sleep or use the sleep function on the scan tool.

20. *When the vehicle has an unacceptable amount of parasitic current drain, remove each fuse one at a time until the current drain falls to an acceptable level. This will indicate which circuit is causing the drain. Refer to Power Distribution Schematics to diagnose exactly which part of the suspect circuit is causing the parasitic drain. In some cases a non-fused circuit or component, such as a relay, is the cause of excessive parasitic current drain.

*Repeat the parasitic current drain test procedure after any repair has been completed to make sure that the parasitic current drain is at an acceptable level.

*When the cause of the excessive current drain has been located and repaired, remove the J 38758.

21. Connect the battery negative cable to the battery negative terminal.

Note: See PIC4798 for further information on battery diagnostic on cars/trucks equipped with class 2 data networks.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.