B1935
DTC B1935 or B2180
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions 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 must be powered.
Conditions for Setting the DTC
The heated seat system must be active.
B1935 and B2180 04
The MSM does not detect a temperature change for up to 210 seconds.
B1935 and B2180 0A
The MSM detects that the set point temperature has not been reached for up to 8.5 minutes.
B1935 and 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 less than the minimum resistance value of 2.4 ohms.
B1935 and 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 greater than the maximum resistance value of 10 ohms.
B1935 and B2180 1F
The temperature sensor voltage is erratic or changes suddenly.
Action Taken When the DTC Sets
The heated seat back function for the appropriate seat will be disabled.
Conditions for Clearing the DTC
* The current DTC clears 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.
Circuit/System Testing
B1935
1. Ignition OFF, disconnect the X1 harness connector at the MSM.
2. Ignition OFF, test for less than 10 ohms between the heater element supply voltage circuit terminal 14 and the control circuit terminal 4.
^ If greater than the specified range, test the supply voltage circuit and the control circuits 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 8-11 ohms between the signal circuit terminal 3 X5 and the low reference circuit terminal 5 X2.
^ 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 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.
B2180
1. Ignition OFF, disconnect the X1 and X4 harness connector at the MSM.
2. Ignition OFF, test for less than 10 ohms between the supply voltage circuit terminal 14 X1 and the control circuit terminal 14 X4.
^ 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 8-11 ohms between the signal circuit terminal 2 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 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 after completing the diagnostic procedure. Verification Tests
* Driver Seat Back Cushion Heater and Passenger Seat Back Cushion Heater Replacement