Subject: | Battery Electrical Drain/Parasitic Load Test |
Models: | All Saturn Models |
This PI was superceded to add keywords GMT201, GMT960 and change the PI number referenced for class-2 diagnosis to PIC4798 from PIC3589C.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.
*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.
*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.
*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.
*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.
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.