Heated/Cooled Seats Inoperative (KB6)
Heated/Cooled Seats Inoperative (Cadillac, KB6)
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
Each seat has two ventilation heating and cooling modules, one located under the seat cushion to control cushion temperature and one located in the seat back to control seat back temperature.
Each ventilation heating and cooling module contains the necessary electronics to control the heating and cooling functions, as well as a thermo-electric device (TED) and blower motor used for the cooling functions. The heating function is provided by a separate heating element which is also controlled by the ventilation heating and cooling module.
In the description below, the TEDs and blower motors are referenced independently even though they are packaged together as indicated above.
The heated and cooled seat switches are located in the HVAC control module. When a heated or cooled seat switch is pressed a serial data message from the HVAC control module is sent to the memory seat module (MSM) indicating the heat/cool seat request. The MSM then sends a low side pulse width modulation (PWM) signal through the heated/cooled seat mode signal circuit to both ventilation and cooling modules for a given seat.
Battery positive voltage is supplied to the ventilation heating and cooling modules through a fuse located in the I/P fuse block.
When a cooled seat request is received, the seat ventilation heating and cooling modules apply voltage to the (TEDs) and a pre-determined voltage to the blower motors. When a heated seat request is received, the seat ventilation heating and cooling modules apply battery voltage and ground through the control circuits to the seat heating elements. In order to determine seat temperature, each ventilation module supplies a 5 V signal and a low reference to the temperature sensors that are attached to the seat cushion and seat back heater elements. The temperature sensors are variable resistors, their resistance changes as the temperature of the seat changes. Then based on the seat temperature, the ventilation module controls the voltage level that it applies to the TED and blower motor when in the cool mode, or it cycles the power supply to the heater element ON and OFF when in the heat mode.
Reference Information
Schematic Reference
Heated/Cooled Seat Schematics [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views Connector End Views By Name
Description and Operation
Heated/Cooled Seats Description and Operation Heated/Cooled Seats
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Verification
1. Ignition ON.
2. Verify the heat and cool seat symbols listed below are displayed on the HVAC control screen after pressing the appropriate heated or cooled seat switch.
* Seat back and cushion heat mode symbol
* Seat back only heat mode symbol
* Seat cool mode symbol
• If any symbol is not displayed
Replace the HVAC control module.
• If all symbols are displayed
3. Verify the heated and cooled seat functions listed below operate in all three modes of operation:
* Seat back and cushion heat mode
* Seat back only heat mode
* Seat cool mode
• If both heat and cooled seat functions are inoperative
Refer to Circuit/System Testing - Heated and Cooled Seat Circuit Test.
• If just the heat function is inoperative
Refer to Circuit/System Testing - Heated and Cooled Seat Circuit Test.
• If just the cooled seat function is inoperative
Replace the seat ventilation heating and cooling ventilation module.
• If both the heat and cooled seat functions operate
4. All OK.
Circuit/System Testing
Heated and Cooled Seat Circuit Test
Note: Circuit/System Verification must be performed before proceeding with Circuit/System Testing.
1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the appropriate seat cushion or seat back ventilation heating and cooling module. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 10 ohms between the ground circuit terminal C and ground.
• If 10 ohms or greater
1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 10 ohms
3. Ignition ON.
4. Verify a test lamp illuminates between the B+ circuit terminal A and ground.
• If the test lamp does not illuminate and the circuit fuse is good
Test for less than 2 ohms in the B+ circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, verify the circuit fuse is not open and there is voltage at the fuse.
• If the test lamp does not illuminate and the circuit fuse is open
1. Ignition OFF.
2. Test for infinite resistance between the B+ circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the appropriate seat cushion or seat back ventilation heating and cooling module.
• If the test lamp illuminates
5. Connect a test lamp between the signal circuit terminal B and B+, ignition ON.
6. Verify the test lamp turns ON while the pressing the HEAT or COOL seat switch through the high, medium, and low positions until the OFF position is reached.
• If the test lamp does not turn ON
1. Ignition OFF, disconnect the X6 harness connector at the memory seat module, ignition ON.
2. Test for less than 1 V between the signal circuit and ground.
• If greater than 1 V, repair the short to voltage on the circuit.
• If less than 1 V
3. Test for less than 2 ohms in the signal circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the memory seat module.
• If the test lamp does not turn OFF
1. Ignition OFF, disconnect the X6 harness connector at the memory seat module.
2. Test for infinite resistance between the signal circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the memory seat module.
• If the test lamp turns ON and OFF
7. Test for 500 ohms-300 kohms between the signal circuit terminal D and the low reference circuit terminal E.
• If less than 500 ohms
1. Ignition OFF, disconnect the harness connector at the seat heating element.
2. Test for infinite resistance between the signal and low reference circuits.
• If less than infinite resistance, repair the short between the circuits.
• If infinite resistance, test or replace the seat heating element.
• If greater than 300 kohms
1. Ignition OFF, disconnect the harness connector at the seat heating element.
2. Test for less than 2 ohms in the signal and low reference circuits end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the seat heating element.
• If between 500 ohms-300 kohms
8. Ignition OFF, connect the harness connector at the seat ventilation heating and cooling ventilation module and disconnect the harness connector at the seat heating element.
9. Ignition ON.
10. Test for 4.8-5.2 V between the signal circuit terminal C and ground.
• If less than 4.8 V
1. Ignition OFF, disconnect the harness connector at the ventilation heating and cooling module.
2. Test for infinite resistance between the signal circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. Test for less than 2 ohms in the signal circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the ventilation heating and cooling module.
• If greater than 5.2 V
1. Ignition OFF, disconnect the harness connector at the ventilation heating and cooling module, ignition ON.
2. Test for less than 1 V between the signal circuit and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the ventilation heating and cooling module.
• If between 4.8-5.2 V
11. Replace the seat ventilation heating and cooling ventilation module.
Heated Seat Circuit Test
Note: Circuit/System Verification must be performed before proceeding with Circuit/System Testing.
1. Ignition OFF, disconnect the harness connector at the appropriate seat cushion or seat back ventilation heating and cooling module.
2. Test for 3-8 ohms between control circuit terminal F and control circuit terminal G.
• If less than 3 ohms
1. Ignition OFF, disconnect the harness connector at the seat heating element.
2. Test for infinite resistance between the control circuits.
• If less than infinite resistance, repair the short between the control circuits.
• If infinite resistance, replace the seat heating element.
• If greater than 8 ohms
1. Ignition OFF, disconnect the harness connector at the seat heating element.
2. Test for less than 2 ohms in the control circuits end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, test or replace the seat heating element.
• If between 3-8 ohms
3. Test for Infinite resistance between the control circuit terminal F and ground.
• If less than infinite resistance
Repair the short to ground on the circuit.
• If infinite resistance
4. Ignition ON.
5. Test for less than 1 V between the control circuit terminal G and ground.
• If 1 V or greater
Repair the short to voltage on the circuit.
• If less than 1 V
6. Replace the seat ventilation heating and cooling ventilation module.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Driver or Passenger Seat Back Ventilation Heating and Cooling Blower Replacement Driver or Passenger Seat Back Ventilation Heating and Cooling Blower Replacement
* Driver or Passenger Seat Cushion Ventilation Heating and Cooling Blower Replacement Driver or Passenger Seat Cushion Ventilation Heating and Cooling Blower Replacement
* Control Module References Control Module References for the climate control seat module and memory seat module replacement, programming and setup