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 Descriptor
DTC B1420: Device VoltageDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
MSM B+ Terminal B11 X2 | B1420 | B1420 | -- | -- |
MSM B+ Terminal A X1 | 1 | 1 | -- | -- |
Seat Adjuster Switch B+ | B1420 | 1 | -- | -- |
Power Seat Front Vertical Up Switch Signal | B1420 | 1 | B1735, B1740, B1745, B1750, B1755, B1760 | -- |
Power Seat Front Vertical Down Switch Signal | B1420 | 1 | B1735, B1740, B1745, B1750, B1755, B1760 | -- |
Power Seat Horizontal Rearward Switch Signal | B1420 | 1 | B1735, B1740, B1745, B1750, B1755, B1760 | -- |
Power Seat Horizontal Forward Switch Signal | B1420 | 1 | B1735, B1740, B1745, B1750, B1755, B1760 | -- |
Power Seat Rear Vertical Up Switch Signal | B1420 | 1 | B1735, B1740, B1745, B1750, B1755, B1760 | -- |
Power Seat Rear Vertical Down Switch Signal | B1420 | 1 | B1735, B1740, B1745, B1750, B1755, B1760 | -- |
1. Power seat inoperative | ||||
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. The memory seat module (MSM) monitors this voltage to verify that power is supplied to the seat adjuster switch before it will allow for any memory recall operation.
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 if the MSM detects an open on the B+ circuit.
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 is also referred to as the Driver Position Module in certain scan tool menus.
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Memory Seats Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
Ignition ON, observe the scan tool Driver Position Module seat switch parameters while activating each switch. The reading should change between Inactive and Active as each switch is activated.
Circuit/System Testing
- Ignition OFF, disconnect the X2 harness connector at the MSM.
- Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal B11 and ground.
- If all circuits test normal, replace the MSM.
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the seat adjuster switch signal circuits for a short to ground. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for MSM replacement, setup, and programming |
