Diagnostic Aids

Active Draws 

• If the battery voltage is interrupted by removing fuses, relays, module or component connectors, or disconnecting the battery may cause the condition to clear or reset. To prevent a loss of power when disconnecting the battery install the EQPMSK6211 Battery Booster Pack or equivalent to the positive and negative battery cables prior disconnecting it to prevent a loss of voltage.
• Verify no aftermarket accessories are installed or connected to the Auxiliary Power Ports, Audio Ports, or DLC. e.g. insurance snapshot or tracking devices.
• On Some Vehicles the Auxiliary Power Ports can have B+ at all times (not controlled by RAP) by relocating the fuse in the fuseblock.
• Aftermarket accessories installed into the courtesy lamp circuit may cause the inadvertent power timer in the K9 Body Control Module (BCM) to keep resetting. This may cause the BCM to remain awake and cause a current drain on the battery.
• Verify that the battery and charging system are operating correctly. Refer to Battery Charging , and Charging System Test .
• An engine off natural vacuum evaporative test can occur if the Engine Control Module (ECM) determines the drive cycle has met the appropriate criteria immediately after key off. The ECM will stay awake and the vent solenoid will stay energized for up to 45 min. The typical current draw for this is approximately 1 A.
• The K9 Body Control Module has discrete input and output terminals to control the vehicle's body functions. The K9 Body Control Module is wired to the High Speed GMLAN bus, Low Speed GMLAN bus and multiple Local Interconnect Network (LIN) buses and acts as a gateway between them. The various K9 Body Control Module input and output circuits are illustrated in the corresponding functional areas on the K9 Body Control Module electrical schematics.
• The K9 Body Control Module functions as the power mode master. The ignition switch is a low current switch with multiple discrete ignition switch signals to the power mode master for determining the power mode that will be sent over the serial data circuits to the other devices that need this information; the power mode master will activate relays and other direct outputs of the power mode master as needed. Refer to Power Mode Description and Operation for a complete description of power mode functions.
• The K9 Body Control Module functions as a gateway or translator. The purpose of the gateway is to translate serial data messages between the High Speed GMLAN bus and the Low Speed GMLAN bus for communication between the various devices. The gateway will interact with each network according to that network's transmission protocol. All communication between the K9 Body Control Module and a scan tool is done through the primary High Speed GMLAN bus.
• Generation 5 and prior OnStar module does can "wake up" every 10 minutes for the first 48 hours, for Generation 6 and later the current draw is very low, less than 40 mA, the OnStar system is left in that state for up to the first 48 h. a parasitic draw of up to 40 mA with an occasional spike as high as 80 mA for the first 48 hours is normal. If Equipped Refer to OnStar Description and Operation OnStar Sleep Cycle.
• Some automatic climate control systems can remain in a semi awake state for up to three hours, actual draw amounts vary by vehicle platform but are typically not greater than 50 mA.
• An extremely low mA current level is consumed by the body control module for monitoring purposes, actual system wake up occurs when the fobs for the vehicle are activated or approach is detected on keyless access vehicles. Other devices that operate on the same remote keyless entry frequency, such as the tire pressure monitoring sensors and other vehicle Fobs in the vicinity, may cause the body control module to have a 100 mA spike. These spikes are normal and occur too briefly to have a significant effect on battery drain.
• If an excessive current draw is not present during initial testing, continue periodic testing over a 1 - 2 hour period to see if the current draw increases and stays above an unacceptable level.
NOTE:

The battery specification listed below is a generic specification. Refer to the label on the original battery when testing the battery.

• The battery run down time will vary depending on the batteries reserve capacity. If the reserve capacity is higher, then the battery run down time may be longer. If the reserve capacity is lower, then the battery run down time may be shorter. The graph below indicates roughly how many days a 690 cold cranking amperage battery with a 110 min. reserve capacity starting at 80 percent state of charge will last with a constant current draw until it reaches 50 percent state of charge. Differences in battery reserve capacity and temperature will affect the results.

Intermittent Draws 

• The Battery Draw Customer Verification Worksheet may be helpful isolating or duplicating the customers concern CCVS - Battery Draw
• When diagnosing an intermittent battery draw, if the battery voltage is interrupted by removing fuses, relays, module or component connectors, or disconnecting the battery may cause the condition to clear or reset. To prevent a loss of power when disconnecting the battery install the EQPMSK6211 Battery Booster Pack or equivalent to the positive and negative battery cables prior disconnecting it to prevent a loss of voltage.
• Verify no aftermarket accessories are installed or connected to the Auxiliary Power Ports, Audio Ports, or DLC. e.g. insurance snapshot or tracking devices.
• On Some Vehicles the Auxiliary Power Ports can have B+ at all times (not controlled by RAP) by relocating the fuse in the fuseblock.
• Rule out customer driving habits such as regular short trips that do not allow enough time to properly charge the battery. Refer to Battery Description and Operation .
• Verify that the battery and charging system are operating correctly. Refer to Battery Charging , and Charging System Test .
• A battery discharging for no apparent reason while the vehicle is parked can be caused by an intermittent draw, such as a module waking up, or a continuous draw, such as a dome light or stuck relay.
• An engine off natural vacuum evaporative test can occur if the Engine Control Module (ECM) determines the drive cycle has met the appropriate criteria immediately after key off. The ECM will stay awake and the vent solenoid will stay energized for up to 45 min. The typical current draw for this is approximately 1 A.
• The K9 Body Control Module has discrete input and output terminals to control the vehicle's body functions. The K9 Body Control Module is wired to the High Speed GMLAN bus, Low Speed GMLAN bus and multiple Local Interconnect Network (LIN) buses and acts as a gateway between them. The various K9 Body Control Module input and output circuits are illustrated in the corresponding functional areas on the K9 Body Control Module electrical schematics.
• The K9 Body Control Module functions as the power mode master. The ignition switch is a low current switch with multiple discrete ignition switch signals to the power mode master for determining the power mode that will be sent over the serial data circuits to the other devices that need this information; the power mode master will activate relays and other direct outputs of the power mode master as needed. Refer to Power Mode Description and Operation for a complete description of power mode functions.
• The K9 Body Control Module functions as a gateway or translator. The purpose of the gateway is to translate serial data messages between the High Speed GMLAN bus and the Low Speed GMLAN bus for communication between the various devices. The gateway will interact with each network according to that network's transmission protocol. All communication between the K9 Body Control Module and a scan tool is done through the primary High Speed GMLAN bus.
• Generation 5 and prior OnStar module does can "wake up" every 10 minutes for the first 48 hours, for Generation 6 and later the current draw is very low, less than 40 mA, the OnStar system is left in that state for up to the first 48 h. a parasitic draw of up to 40 mA with an occasional spike as high as 80 mA for the first 48 hours is normal. Refer to OnStar Description and Operation OnStar Sleep Cycle.
• Some automatic climate control systems can remain in a semi awake state for up to three hours, actual draw amounts vary by vehicle platform but are typically not greater than 50 mA.
• An extremely low mA current level is consumed by the body control module for monitoring purposes, actual system wake up occurs when the fobs for the vehicle are activated or approach is detected on keyless access vehicles. Other devices that operate on the same remote keyless entry frequency, such as the tire pressure monitoring sensors and other vehicle Fobs in the vicinity, may cause the body control module to have a 100 mA spike. These spikes are normal and occur too briefly to have a significant effect on battery drain.
• If an excessive current draw is not present during initial testing, continue periodic testing over a 1 - 2 hour period to see if the current draw increases and stays above an unacceptable level.
NOTE:

The battery specification listed below is a generic specification. Refer to the label on the original battery when testing the battery.

• The battery run down time will vary depending on the batteries reserve capacity. If the reserve capacity is higher, then the battery run down time may be longer. If the reserve capacity is lower, then the battery run down time may be shorter. The graph below indicates roughly how many days a 690 cold cranking amperage battery with a 110 min. reserve capacity starting at 80 percent state of charge will last with a constant current draw until it reaches 50 percent state of charge. Differences in battery reserve capacity and temperature will affect the results.