A dead battery as well as several other conditions, including slow engine crank, inoperative Auto Stop/Start (if equipped), radio on or fades out slowly after the ignition is off, and inoperative front or rear heated seats, may be found on some 2019-2020 Silverado 1500 and Sierra 1500 models. LIN Bus DTCs U1524, U1526, U1555, and U155D also may be set.
These conditions may be caused by the Body Control Module (BCM) staying awake due to an input from a LIN Bus. In many cases, the BCM is misdiagnosed as being at fault and is unnecessarily replaced.
There are two known areas that can short out LIN Bus circuits 6133 and/or 4115 for the front/rear heated seats. If this occurs, the BCM may stay awake and draw down the battery. Keep in mind that even if a truck is not equipped with rear heated seats, these circuits are still in the harness.
Inspect for a pinched body harness under the left rear seat where the seatback is attached to the back of cab. (Fig. 11)
Fig. 11
Connector X370 is shown on a truck that was not equipped with rear heated seats. (F12) In this example, LIN Bus circuit 6133 was shorted to the B+ circuit in the harness.
Fig. 12
In addition, inspect connector X225 for terminal issues/corrosion. As shown, the LIN Bus circuit 4115 was corroded (Fig. 13) and shorting to other terminals in the connector.
Fig. 13
If corrosion is found at connector X225, inspect for a water leak. Water may be entering at the A-pillar grommet for the door pass-through connector if the grommet is not fully seated.
If any issues are found, follow the Wiring and Connector Repair instructions in the appropriate Service Information to correct the condition.
Refer to #PIT5750A for additional information.
– Thanks to Jim Miller
