B1870 Driver Belt Tower Up Switch CKT Malf (A45 With AL2)

DTC B1870 Driver Belt Tower Up Switch CKT Malf (A45 With AL2):

CIRCUIT DESCRIPTION
The Memory Seat Module (MSM) receives an input from the seat switch headrest switch when the switch is actuated. When the headrest switch is operated in the up direction, battery positive voltage (B+) is supplied to the MSM headrest up input via CKT 1065 (WHT/BLK). The MSM recognizes the input and moves the headrest in the up direction.

CONDITIONS FOR SETTING DTC
^ When the headrest up switch is active for 30 seconds after motion has ceased, the switch will be considered shorted and the DTC will set.
^ If the seat headrest position sensor DTC B1900 is current and the headrest up switch is active for 30 seconds, the switch will be considered shorted and the DTC will set.
^ DTC B1870 will set only if DTC B1327 MSM or DTC B1328 MSM is not current.

ACTION TAKEN WHEN THE DTC SETS
^ The MSM will not move the headrest in the up direction.
^ The MSM will continue to respond to valid inputs from the other manual switches.
^ All memory recall function commands will be ignored for all directions.

CONDITIONS FOR CLEARING DTC
^ The MSM sees that the headrest up switch is no longer active.
^ Use the On-Boards clearing DTCs feature.
^ Use a scan tool.

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table:
1. Perform the entire Power Seat Systems Diagnostic System Check before continuing with the diagnosis of this DTC.
2. Determines whether there is a stuck switch or a short to battery positive voltage (B+) in the wiring input to the memory seat module (MSM). DTC B1870 will set again if there is a short in the wiring or there is an internal MSM problem. DTC B1870 will not set again if there is a stuck switch because the switch has been disconnected from the memory seat module (MSM) input.
3. Determines whether there is a short to battery positive voltage (B+) in the input wiring to the MSM.
7. Clear all DTCs after the repair procedure is complete.