2018 - 2019 Corvette: GM TechLink: Intermittent Parasitic Battery Draw Below 40° F/4° C

Intermittent Parasitic Battery Draw Below 40° F/4° C

June 16, 2020
GM TechLink

Several intermittent conditions related to a low battery state of charge may be found on some 2018 - 2019 ATS, CTS, XTS, Corvette; 2018 - 2020 Envision, LaCrosse, CT6, Escalade, XT5, Equinox, Impala, Malibu, Camaro, Silverado, Suburban, Tahoe, Traverse, Acadia, Sierra, Terrain, Yukon; 2019 - 2020 XT4, Blazer; and 2020 XT6 models.

The following low battery charge conditions may be present when the ambient air temperature is below 40° F/4° C for an extended period of time:

• Dead battery/required jump start
• Slow crank
• Battery low state of charge and, if equipped, Auto Stop/Start inoperative
• Instrument cluster backlighting turning on intermittently while the vehicle should be asleep
• Keyless or passive entry/start inoperative

These conditions are not easily duplicated in the service bay or in temperatures above 40° F/4° C.

These conditions may be due to a low battery state of charge that is being caused by one or more modules waking up the Low Speed GM LAN Bus. When the ambient air temperature is below 40° F/4° C, the Seat Memory Control Module (SMCM) could inadvertently wake up the Low Speed GM LAN Bus. All SMCM’s on a vehicle, including the Driver K40 (Fig. 9), Passenger K40P, Left Rear K40LR and/or Right Rear K40RR module, may apply.

Fig. 9

Begin diagnosis by asking the customer or inspecting the vehicle for any aftermarket equipment. If no aftermarket equipment is installed, try to duplicate the conditions by leaving the vehicle outside overnight in temperatures below 40° F/4 C.

Follow the Battery Electrical Drain/Parasitic Load Test procedure in the appropriate Service Information. If an excessive battery draw is duplicated, as part of the Circuit/System Testing procedure, remove the fuse(s) that powers the SMCM. The SMCM may be powered by more than one fuse. Wait several minutes to see if the vehicle will return to an acceptable battery draw level. If so, replace the appropriate SMCM.

If the battery draw does not return to an acceptable level with the SMCM fuse(s) removed, then continue with the diagnostic procedures in the Service Information.

– Thanks to Jim Miller