Bulletin No.: PIC6397A
Published date: 10/27/2020

Preliminary Information
PIC6397A Battery Draw - Unable to Turn The Engine O Diagnostic Tips
Models
Brand:
Chevrolet

Model:
Camaro

Model Years:
2016 - 2021

VIN:
from
All

Engine:

to
All

All

Transmissions:
All

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Involved
Region or North America
Country
Some customers may comment on a dead battery when they attempt to start the vehicle. Depending
on when this issue may occur, the customer may be unable to turn the engine o . He or she may press
Condition the Ignition Mode Switch (IMS) but the engine continues to run. Technicians may also nd a parasitic
battery draw.
This concern may be caused by unwanted voltage that is present on the bus of ignition fuses that are
normally powered up by the Ignition Main Relay (KR73) in the Underhood Fuse Block (X50A). These
fuses should have 0v present when the ignition is turned o . If there is any voltage present at all, this
Concern may keep the Ignition Main Relay (KR73) powered up and the customer / tech may be unable to turn
the engine o . The servicing technician will have to check for the presence of voltage on this bus using
a Digital Multimeter (DMM). A test lamp will not work to diagnose this concern. As little as 2-3 volts on
this bus may be enough to keep this relay powered up.

Correction:

To diagnose this potential concern, rst remove each individual fuse, one at a time, on this ignition bus and verify
that the concern has been resolved. This will narrow the concern down to one speci c fused circuit so diagnosis
can be continued. While it is possible that this unwanted backfed voltage may originate from any of these fused
branches, two common issues have been seen in the eld. The rst issue that has been identi ed has been the
use of aftermarket accessories that are powered up by any of the fuses on this bus. If anything aftermarket is
found on the vehicle, simply disconnect it and reevaluate the concern. The second common area of concern
is related to the F40UA fused branch. This particular fuse powers the Seat Heating Control Module. This
module may short out, causing unwanted voltage on circuit 639. This backfed voltage will typically keep the
Ignition Main Relay (KR73) energized. As a quick check to diagnose this concern, remove the F40UA fuse. This is a
yellow 20 amp fuse located in the Underhood Fuse Block (X50A). Once this fuse is removed, check to see if the
engine is able to be turned o . Circuit 639 also branches out to the Rear Body Fuse Block (X53A). If this fuse is
removed and the concern is resolved, continue diagnosis by unplugging the Seat Heating Control Module to verify
that this is the root cause of the concern.

Important: Always check the wiring at the module connector to verify that no circuits are shorted together,
grounded, etc. before replacing a module.

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.

Version History

Version History
Version

2

Modi ed

01/21/2020 - Created on
10/27/2020 - Updated model years

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