Buick Regal: DTC B3920
Diagnostic Instructions
- Perform the Diagnostic System Check - Vehicle prior to using this
diagnostic procedure.
- Review Strategy Based Diagnosis for an overview of the diagnostic
approach.
- Diagnostic Procedure Instructions provides an overview of each
diagnostic category.
DTC Descriptors
DTC B3920
Seat Motors Group 1 Ground Circuit
For symptom byte information refer to Symptom Byte List.
Diagnostic Fault Information
1. All power seat and memory functions are inoperative.
Circuit/System Description
The seat memory control module controls the seat motors via half bridges that
are connected to a power
rail internal to the module. The seat memory control module connects all of the
motor control circuits on
the power rail to a common reference point whenever they are not in operation.
The module monitors all
seat motor control circuits for a shorted to ground or voltage before enabling
any seat motor.
When a power seat switch is pressed or when a memory recall is requested, each
seat motor receives
battery voltage and ground from the seat memory control module via the motor
control circuits. All
motors are reversible, so the direction the motor rotates depends on which
control circuit voltage is
applied and which control circuit ground is applied. When the switch is operated
in the opposite
direction, the module reverses the polarity and applies voltage and ground to
the opposite circuits to
move the seat in the opposite direction.
Conditions for Running the DTC
- DTC B1325 must not be present.
- Module battery voltage must be between 9 - 16 V.
Conditions for Setting the DTC
B3920 00
Current out of the module does not match the current returning to the module
from 1.5 - 5 A.
B3920 01
The voltage on any power rail 1 motor control circuit exceeds 2.78 V for 100
ms.
B3920 02
The voltage on any power rail 1 motor control circuit is below 1.47 V for 100
ms.
B3920 0B
The differential current measured through the high and low side of the power
rail is within tolerance of
each other, but the absolute current or an over-current has exceeded the maximum
value.
Action Taken When the DTC Sets
The seat memory control module will not allow operation of any motor on the
power rail for which the
DTC was set.
Conditions for Clearing the DTC
- The current DTC clears when the fault is no longer present and the power
mode changes to
ignition OFF then back to ignition ON.
- The history DTC will clear after 40 consecutive fault-free ignition
cycles have occurred.
Reference Information
Schematic Reference
- Driver Seat Wiring Schematics
- Passenger Seat Wiring Schematics
Connector End View Reference
Component Connector End View Index
Description and Operation
Memory Seats Description and Operation
Electrical Information Reference
- Circuit Testing
- Connector Repairs
- Testing for Intermittent Conditions and Poor Connections
- Wiring Repairs
Scan Tool Reference
Control Module References for scan tool information.
Circuit/System Testing
B3920 01 or B3920 02
1. Ignition OFF, disconnect the X3 harness connector at the appropriate seat
memory control module
listed below:
- K40D Seat Memory Control Module - Driver
- K40P Seat Memory Control Module - Passenger
2. Test for infinite resistance between each control circuit terminal listed
below and ground:
- Seat front vertical motor up control terminal 3
- Seat front vertical motor down control terminal 4
- Seat rear vertical motor up control terminal 5
- Seat rear vertical motor down control terminal 6
- Seat horizontal motor forward control terminal 11
- Seat horizontal motor rearward control terminal 12
- Seat recline motor forward control terminal 1
- Seat recline motor rearward control terminal 2
- If less than infinite resistance
Repair the short to ground on the circuit.
- Go to next step: If infinite resistance
3. Ignition ON.
4. Test for less than 1 V between each control circuit terminal listed below and
ground:
- Seat front vertical motor up control terminal 3
- Seat front vertical motor down control terminal 4
- Seat rear vertical motor up control terminal 5
- Seat rear vertical motor down control terminal 6
- Seat horizontal motor forward control terminal 11
- Seat horizontal motor rearward control terminal 12
- Seat recline motor forward control terminal 1
- Seat recline motor rearward control terminal 2
- If 1 V or greater
Repair the short to voltage on the circuit.
- Go to next step: If less than 1 V
5. Replace the K40 Seat Memory Control Module.
B3920 00 or B3920 0B
1. Ignition ON.
2. Clear the current and history DTC.
3. Determine which motor set this DTC by operating each seat motor listed below
one at a time in
both directions. Check for the DTC to set between each motor test.
- M50 Seat Front Vertical Motor
- M55 Seat Rear Vertical Motor
- M51 Seat Horizontal Motor
- M56 Seat Recline Motor
4. Ignition OFF, disconnect the harness connector at the seat motor for which
the DTC set, ignition
ON.
5. Clear the DTC.
6. Verify that DTC B3920 00 or B3920 0B does not set while operating the seat
motor adjuster
switch in both directions.
- If DTC B3920 00 or B3920 0B sets
- Ignition OFF.
- Test for infinite resistance between control circuit terminal 1 and
control circuit terminal 3.
- If less than infinite resistance, repair the short between the
circuits.
- Go to next step: If infinite resistance
- Test for less than 2 Ω in each control circuit end to end.
- If 2 Ω or greater, repair the open/high resistance in the circuit.
- If less than 2 Ω, replace the K40 Seat Memory Control Module.
- Go to next step: If DTC B3920 00 or B3920 0B does not set
7. Test or replace the seat motor.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the repair.
- Front Seat Tilt Adjuster Actuator Replacement
- Driver or Passenger Seat Vertical Adjuster Actuator Replacement
- Driver or Passenger Seat Recliner Actuator Replacement (Except GS) or
Driver or
Passenger Seat Recliner Actuator Replacement (GS)
- Control Module References for K40D Seat Memory Control Module - Driver
or K40P Seat
Memory Control Module - Passenger replacement, programming and setup
READ NEXT:
Diagnostic Instructions
Perform the Diagnostic System Check - Vehicle prior to using this
diagnostic procedure.
Review Strategy Based Diagnosis for an overview of the diagnostic
approach.
Diag
Diagnostic Instructions
Perform the Diagnostic System Check - Vehicle prior to using this
diagnostic procedure.
Review Strategy Based Diagnosis for an overview of the diagnostic
approach.
Diag
NOTE: The following steps must be completed before using the symptom
tables.
1. Perform the Diagnostic System Check - Vehicle before using the Symptom
Tables in order to
verify that all of the follo
SEE MORE:
If equipped with base seats, the
vehicle's front seats have adjustable
head restraints in the outboard
seating positions.
If equipped with GS Model seats,
the vehicle's front seats have head
restraints in the outboard seating
positions that cannot be adjusted.
Warning:
With head restraints that are
Diagnostic Instructions
Perform the Diagnostic System Check - Vehicle prior to using this
diagnostic procedure.
Review Strategy Based Diagnosis for an overview of the diagnostic
approach.
Diagnostic Procedure Instructions provide an overview of each diagnostic
category.
DTC Descriptor
DTC