B2180

DTC B1935 or B2180

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 Descriptors
DTC B1935 04
- Left Seat Back Heater Circuit Open

DTC B1935 0A
- Left Seat Back Heater Circuit Rate of Change Below Threshold

DTC B1935 0B
- Left Seat Back Heater Circuit Current Above Threshold

DTC B1935 0C
- Left Seat Back Heater Circuit Current Below Threshold

DTC B1935 1F
- Left Seat Back Heater Circuit Intermittent

DTC B2180 04
- Right Seat Back Heater Circuit Open

DTC B2180 0A
- Right Seat Back Heater Circuit Rate of Change Below Threshold

DTC B2180 0B
- Right Seat Back Heater Circuit Current Above Threshold

DTC B2180 0C
- Right Seat Back Heater Circuit Current Below Threshold

DTC B2180 1F
- Right Seat Back Heater Circuit Intermittent




Diagnostic Fault Information






Circuit/System Description

The driver and front passenger heated seats are controlled by the memory seat module (MSM). When active, power is applied to the seat cushion and back heater elements through a common voltage supply circuit. Each individual heater element is grounded by the MSM through separate low side drive control circuits. The heater element control circuits are pulse width modulated to ground by the module in order to control the seat temperatures by regulating the current flow through the heater elements. The module then monitors the current flow through the heating elements and the of rate change of the temperature sensor to verify correct heated seat operation.


Conditions for Running the DTC

The MSM is powered and the heated seat must be enabled.


Conditions for Setting the DTC

The heated seat system must be active.

B1935, B2180 04

The MSM does not detect a temperature change for up to 210 seconds.

B1935, B2180 0A

The MSM detects that the set point temperature has not been reached for up to 8.5 minutes.

B1935, B2180 0B

By measuring the current and voltage output to the seat back heating element every 10 seconds, the MSM calculates that the heating element resistance is below the minimum resistance value of 2.4 ohms.

B1935, B2180 0C

By measuring the current and voltage output to the seat back heating element every 10 seconds, the MSM calculates that the heating element resistance is above the maximum resistance value of 10 ohms.

B1935, B2180 1F

The temperature sensor voltage is erratic or changes suddenly.


Action Taken When the DTC Sets

The heated seat function for the affected seat will be disabled.


Conditions for Clearing the DTC

* The current DTC will clear and will the set code to history, when the malfunction is no longer present and the power mode changes to OFF then back to ACC or RUN.
* The history DTC will clear after 50 consecutive fault-free ignition cycles have occurred.



Reference Information
Schematic Reference

Heated/Cooled Seat Schematics ([1][2]Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Heated Seats Description and Operation (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 Testing


DTC B1935
1. Ignition OFF, disconnect the X1 harness connector at the MSM.
2. Ignition OFF, test for less than 10 ohms of resistance between the heater element supply voltage circuit terminal 6 and the control circuit terminal 1.

• If greater than the specified range, test the supply voltage circuit and the control circuit for an open/high resistance. If the circuits test normal, replace the seat back heating element.

3. Ignition OFF, disconnect the X2 and X5 harness connectors at the MSM.
4. Test for 3.2K-300K ohms of resistance between the temperature sensor signal circuit terminal 4 and the low reference circuit terminal 2.

• If greater than the specified range, test the signal and low reference circuits for a short to voltage or an open/high resistance. If the circuits test normal, replace the seat back temperature sensor.


• If less than the specified range, test the signal and low reference circuits for a short to ground. If the circuits test normal, replace the seat back temperature sensor.

5. Connect the X1, X2, and X5 harness connectors at the MSM.
6. Disconnect the harness connector at the seat back heating element/temperature sensor.
7. Ignition ON, test for 4.8-5.2 volts between the temperature sensor signal circuit terminal C and ground.

• If greater than the specified value, test the signal circuit for a short to voltage. If the circuit tests normal, replace the MSM.


• If less than 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.

8. If all circuits test normal, replace the MSM.



DTC B2180
1. Ignition OFF, disconnect the X1 harness connector at the MSM.
2. Ignition OFF, test for less than 10 ohms of resistance between the heater element supply voltage circuit terminal 14 and the control circuit terminal 4.

• If greater than the specified value, test the supply voltage circuit and the control circuit for an open/high resistance. If the circuits test normal, replace the seat back heating element.

3. Ignition OFF, disconnect the X2 and X5 harness connectors at the MSM.
4. Test for 3.2K-300K ohms of resistance between the temperature sensor signal circuit terminal 3 and the low reference circuit terminal 6.

• If greater than the specified range, test the signal circuit and low reference circuit for a short to voltage or an open/high resistance. If the circuits test normal, replace the seat back temperature sensor.


• If less than the specified range, test for a short between the signal and low reference circuits. If the circuits test normal, replace the seat back temperature sensor.

5. Connect the X1, X2, and X5 harness connectors at the MSM.
6. Disconnect the harness connector at the seat back heating element/temperature sensor.
7. Ignition ON, test for 4.8-5.2 volts between the temperature sensor signal circuit terminal C and ground.

• If greater than the specified value, test the signal circuit for a short to voltage. If the circuit tests normal, replace the MSM.


• If less than 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.

8. If all circuits test normal, replace the MSM.



Repair Instructions

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

* Driver Seat Back Cushion Heater and Passenger Seat Back Cushion Heater Replacement (Driver Seat Back Cushion Heater and Passenger Seat Back Cushion Heater Replacement)
* Control Module References (Programming and Relearning) for MSM replacement, setup, and programming