Chevrolet Trax: DTC B3920: Driver seat motors group 1

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 00

Driver Seat Motors Group 1 Common Circuit Malfunction

DTC B3920 01

Driver Seat Motors Group 1 Common Circuit Short to Battery

DTC B3920 02

Driver Seat Motors Group 1 Common Circuit Short to Ground

DTC B3920 42

Driver Seat Motors Group 1 Common Circuit Calibration Not Programmed

DTC B3920 0B

Driver Seat Motors Group 1 Common Circuit High Current

Diagnostic Fault Information

Circuit/System Description

The seat memory control module controls the seat motors via half bridges that are connected to power rails internal to the module. The seat memory control module connects all of the motor control circuits on each power rail to a common reference point whenever they are not in operation. This reference point is biased to approximately 2.5 V. The seat memory control module checks to see if this reference voltage is shorted to ground or battery 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 42

This DTC will set if the module calibration is not programmed.

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 OFF then back to ACC or RUN.
• The history DTC will clear after 40 consecutive fault-free ignition cycles have occurred.

Reference Information

Schematic Reference

Driver Seat Schematics (Encore), Driver Seat Schematics (Trax)

Connector End View Reference

WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX - ENCORE WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX - TRAX

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 X4 and X5 harness connectors at the K40 Seat Memory Control Module.
2. Test for infinite resistance between the control circuit terminals listed below and ground:

• Front vertical motor up control terminal 7 X4
• Front vertical motor down control terminal 8 X4
• Rear vertical motor up control terminal 4 X5
• Rear vertical motor down control terminal 3 X5
• Horizontal motor forward control terminal 2 X5
• Horizontal motor rearward control terminal 1 X5

If less than infinite resistance

Repair the short to ground on the circuit.

If infinite resistance

3. Ignition ON.
4. Test for less than 1 V between the control circuit terminals listed below and ground:

• Front vertical motor up control terminal 7 X4
• Front vertical motor down control terminal 8 X4
• Rear vertical motor up control terminal 4 X5
• Rear vertical motor down control terminal 3 X5
• Horizontal motor forward control terminal 2 X5
• Horizontal motor rearward control terminal 1 X5

If 1 V or greater

Repair the short to voltage on the circuit.

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 the driver seat motors listed below one at a time in both directions. Check for the DTC to set between each motor test.

• M50D Seat Front Vertical Motor - Driver
• M55D Seat Rear Vertical Motor - Driver
• M51D Seat Horizontal Motor - Driver

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

1. Test for infinite resistance between control circuit terminal 1 and control circuit terminal 5.

• If less than infinite resistance, repair the short between the circuits.
• If infinite resistance

2. Test for less than 2 ohms between the control circuit terminals listed below end to end:

• Terminal 1
• Terminal 5

If 2 ohms or greater, repair the open/high resistance in the circuit.

If less than 2 ohms, replace the seat motor.

If DTC B3920 00 or B3920 0B does not set

7. Replace the seat motor.

B3920 42

1. Ignition ON.
2. Verify the DTC is not set.

If the DTC is set

Replace the K40 Seat Memory Control Module.

If the DTC is not set

3. All OK.

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
• Front Seat Adjuster Actuator Replacement
• Control Module References for K40 Seat Memory Control Module replacement, programming and setup

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