Power Seats

DTC B1420

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.



DTC Descriptor
DTC B1420
- Device Voltage




Diagnostic Fault Information






Circuit/System Description

Battery positive voltage is supplied at all times to the seat adjuster switch from the TELE SWITCH/MSM fuse located in the body control module (BCM) fuse block. When a seat adjustment switch is operated, battery voltage is applied through the switch contacts to the appropriate switch signal circuit to the memory seat module (MSM) input to ground. The MSM responds to the input from the adjuster switch by commanding the selected seat motor to move in response to the switch signal.


Conditions for Running the DTC

* DTC B1327 must not be present.
* Battery voltage must be between 9-16 volts.



Conditions for Setting the DTC

DTC B1420 will set when the MSM detects a short to ground on a switch signal circuit or the B+ circuit to the seat adjuster switch or MSM.


Actions Taken When the DTC Sets

* The memory seat functions for the seat will be disabled.
* Manual seat functions will operate.



Conditions for Clearing the DTC

* The condition responsible for setting the DTC no longer exists.
* A history DTC will clear once 50 consecutive malfunction-free ignition cycles have occurred.



Diagnostic Aids

The memory seat module (MSM) is also referred to as the driver position module (DPM) in certain scan tool menus.


Reference Information
Schematic Reference

Driver Seat Schematics (Driver Seat Schematics)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Memory Seats Description and Operation (Memory Seats Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning)


Circuit/System Verification

Ignition ON, observe the scan tool seat switch parameters located in the driver position module data display menu while activating each switch. The reading should change between ACTIVE and INACTIVE as each switch is activated.


Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the driver seat adjuster switch.
2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal E and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

3. Ignition ON, verify the scan tool seat switch parameters display INACTIVE for all switches.

• If the scan tool displays ACTIVE, test the appropriate switch signal circuit for a short to voltage. If the circuit tests normal, replace the MSM.

4. Install a 3 A fused jumper wire between the B+ circuit terminal E and the inoperative switch signal circuit. Verify the appropriate scan tool seat switch parameter is ACTIVE.

• If not the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the MSM.

5. If all circuits test normal, test or replace the driver seat adjuster switch.



Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Power Seat Switch Replacement (Power Seat Switch Replacement)
* Control Module References (Programming and Relearning) for MSM replacement, setup, and programming