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 Descriptors
DTC B1AA0: Driver Seat Cushion Temperature Sensor Circuit OpenDTC B1AA1: Driver Seat Back Temperature Sensor Circuit Open
DTC B2730: Driver Seat Back Over Temperature
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Battery Positive Voltage | 1 | 1 | -- | -- |
Ignition 3 Voltage | 1 | 1 | -- | -- |
Driver Seat Blower Supply Voltage | B103D | B272E | B272E | -- |
Driver Seat Back Blower Supply Voltage | B103D | B272C, B727E, B2730 | B272E | -- |
Driver Seat Cushion Blower Supply Voltage | B103D | B272C, B2729 | B272E | -- |
Driver Heated Seat Back Only Mode Switch Signal | 5 | 5 | 5 | -- |
Driver Heated Seat Cool Switch Signal | 4 | 4 | 4 | -- |
Driver Seat Back Cushion Switch Signal | 3 | 3 | 3 | -- |
Driver Seat Back Temperature Sensor Signal | B272C, B2730 | B1AA1, B272C | B1AA1, B272C | -- |
Driver Seat Cushion Temperature Sensor Signal | B272C, B2729 | B1AA0, B272C | B1AA0, B272C | -- |
Left Heated/Cooled Seat Mode Signal | 2 | 2 | 2 | -- |
Driver Seat Back Heated/Cool Ventilation Module Cool Control | B103A | B272C, 4, 5 | -- | -- |
Driver Seat Back Heated/Cool Ventilation Module Heat Control | B103A, 4 | B272C, 4, 5 | -- | -- |
Driver Seat Cushion Heated/Cool Ventilation Module Cool Control | B103A | B272C, 4 | -- | -- |
Driver Seat Cushion Heated/Cool Ventilation Module Heat Control | B103A, 4 | B272C | 4 | -- |
Driver Seat Back Blower Speed Control | B19A8 | B272C, B272E, B2730 | B19A4 | -- |
Driver Seat Cushion Blower Speed Control | B19A7 | B272C, B2729 | B19A3 | -- |
Low Reference - Driver Heated Seat Switch | -- | 2 | -- | -- |
Low Reference - Driver Seat Back Blower | -- | B272C, B272E, B2730 | -- | -- |
Low Reference - Driver Seat Back and Cushion Blower | -- | B272E | -- | -- |
Low Reference - Driver Seat Cushion Blower | -- | B272C, B2729 | -- | -- |
Low Reference - Driver Seat Back Temperature Sensor | -- | B1AA1, B272C | -- | -- |
Low Reference - Driver Seat Cushion Temperature Sensor | -- | B1AA0, B272C | -- | -- |
Ground - Climate Control Seat Module | -- | 1 | -- | -- |
1. Driver and passenger heated/cooled seats are inoperative, the CCSM does not communicate with the scan tool. 2. Driver heated and cooled seat inoperative 3. Seat heat mode is inoperative 4. Seat cool mode is inoperative 5. Heated/cooled seat inoperative - Back Only Mode | ||||
Circuit/System Description
The heat and cool seat functions for the driver and passenger seats are controlled by the climate control seat module (CCSM) that is located under the passenger seat cushion. When a driver or passenger heat or cool seat switch is pressed, a low reference signal is applied through the switch signal circuit to the door control module. In response to the switch input, the door module sends a GMLAN message to the memory seat module (MSM) indicating the heat/cool seat request. The MSM then sends a pulse width modulation (PWM) signal through the heated/cooled seat mode signal circuit to the CCSM. The CCSM then applies battery positive voltage to the seat cushion and seat back thermal electronic devices (TEDs) and a pre-determined voltage to the blower motors. To determine seat temperature, the CCSM supplies a 5-volt signal and a low reference to the temperature sensors that are attached to each TED. The temperature sensors are variable resistors, their resistance changes as the temperature of the seat changes. Then based on the seat temperature, the CCSM controls the voltage level that it applies to the TEDs and blower motors.
Conditions for Running the DTC
Ignition ON and the driver heat or cool seat is commanded On.
Conditions for Setting the DTC
B1AA0
The CCSM detects the driver seat cushion temperature sensor voltage is greater than 4.73 volts or 242 counts for more than 4 seconds.
B1AA1
The CCSM detects the driver seat back temperature sensor voltage is greater than 4.73 volts or 242 counts for more than 4 seconds.
B2730
| • | The CCSM detects an open in the seat cushion blower speed control circuit. |
| • | The CCSM detects a short to ground on the driver seat back temperature sensor signal circuit for more than 4 seconds. |
Action Taken When the DTC Sets
The CCSM will disable the heat or cool seat function for the current ignition cycle.
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.
Diagnostic Aids
In order to perform valid tests when diagnosing the climate control seat (CCS) system, the ignition must be cycled OFF then ON between each test in order to reset the CCSM.
Reference Information
Schematic Reference
Connector End View Reference
Heated/Cooled Seat Connector End Views
Description and Operation
Heated/Cooled Seats Description and Operation
Electrical Information Reference
Scan Tool Reference
Circuit System Verification
- Ignition ON, verify the scan tool Seat 1 Cushion Temp parameter is between 0.5-4.73 volts.
- Verify the scan tool Seat 1 Back Temp parameter is between 0.5-4.73 volts.
- If the seat cushion and back temperature parameters displayed correctly on the scan tool, refer to the B1AA1, B2730 - Seat Back Temperature Sensor and Blower Test.
| ⇒ | If not within the specified range, refer to B1AA0 - Seat Cushion Temperature Sensor Test. |
| ⇒ | If not within the specified range, refer to B1AA1, B2730 - Seat Back Temperature Sensor and Blower Test. |
Circuit/System Testing
B1AA0 - Seat Cushion Temperature Sensor Test
- Ignition OFF, disconnect the C2 harness connector at the CCSM.
- Test for 300 Ω-18 k Ω between the signal circuit terminal 7 and the low reference circuit terminal 8.
- Connect the C2 harness connector at the CCSM.
- Disconnect the harness connector at the seat cushion ventilation heat and cool module.
- Ignition ON, test for 4.8-5.2 volts between the signal circuit terminal 5 and ground.
- If all circuits test normal, replace the CCSM.
Important: If the resistance is measured with the seat still warm or cool, the resistance values will vary. At 68°F (20°C), the nominal resistance value is 1200 Ω ±5 percent. For warmer or cooler ambient temperatures, refer to the Temperature vs Resistance table below. The delta resistance values between the seat cushion and seat back temperature sensors should not be greater than 2000 Ω.
| ⇒ | 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, test or replace the seat cushion ventilation heat and cool module. |
| ⇒ | If less than the specified range, test for a short between the signal and low reference circuits. If the circuits test normal, test or replace the seat cushion ventilation heat and cool module. |
| ⇒ | If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the CCSM. |
| ⇒ | If less than the specified range, test the signal circuit for a short to ground. If the circuits tests normal, replace the CCSM. |
B1AA1, B2730 - Seat Back Temperature Sensor and Blower Test
- Ignition OFF, disconnect the C2 harness connector at the CCSM.
- Test for 300 Ω-18 kΩs between the signal circuit terminal 9 and the low reference circuit terminal 10.
- Connect the C2 harness connector at the CCSM.
- Disconnect the harness connector at the seat back ventilation heat and cool module.
- Ignition ON, test for 4.8-5.2 volts between the signal circuit terminal 5 and ground.
- Connect a test lamp between the supply voltage circuit terminal 2 and ground.
- Ignition ON, command the Driver Seat Blower Cmd. ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
- Connect a test lamp between the control circuit terminal 7 and ground.
- Ignition ON, command the Driver Seat Blower Cmd. ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
- If all circuits test normal, test or replace the seat back ventilation heat and cool module.
Important: If the resistance is measured with the seat still warm or cool, the resistance values will vary. At 68°F (20°C), the nominal resistance value is 1200 Ω ±5 percent. For warmer or cooler ambient temperatures, refer to the Temperature vs Resistance table below. The delta resistance values between the seat cushion and seat back temperature sensors should not be greater than 2000 Ω.
| ⇒ | 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, test or replace the seat cushion ventilation heat and cool module. |
| ⇒ | If less than the specified range, test for a short between the signal and low reference circuits. If the circuits test normal, test or replace the seat cushion ventilation heat and cool module. |
| ⇒ | If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the CCSM. |
| ⇒ | If less than the specified range, test the signal circuit for a short to ground. If the circuits tests normal, replace the CCSM. |
| ⇒ | If the test lamp does not illuminate, test the supply circuit for a short to ground or an open/high resistance. If the circuit test normal, replace the CCSM. |
| ⇒ | If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance. If the circuit test normal, replace the CCSM. |
Component Testing
Ventilation Heat and Cool Module
- Ignition OFF, disconnect the harness connector at the appropriate seat cushion or seat back ventilation heat and cool module.
- Test for 300 Ω-18 kΩ between the signal circuit terminal 5 and the low reference circuit terminal 8.
- Test for 0.9-10 Ω between control circuit terminal 1 and control circuit terminal 3.
- Test for 6 k-9 kΩ between control circuit terminal 2 and the low reference circuit terminal 4.
- Test for 290 k-420 kΩ between control circuit terminal 7 and the low reference circuit terminal 4.
Important: If the resistance is measured with the seat still warm or cool, the resistance values will vary. At 68°F (20°C), the nominal resistance value is 1200 Ω ±5 percent. For warmer or cooler ambient temperatures, refer to the Temperature vs Resistance table below. The delta resistance values between the seat cushion and seat back temperature sensors should not be greater than 2000 Ω.
| ⇒ | If not within the specified range, replace the ventilation heat and cool module. |
Important: The test leads must be connected in the correct polarity, otherwise lower out of range values will appear. Use the Positive Lead for the COOL control circuit and the Negative Lead for the HEAT control circuit. If the
resistance is measured with the seat still warm or cool, the resistance values will vary even if the system was powered up for just a few seconds. The TED must be allowed to stabilize to room temperature prior to a measurement. The following conditions will
change the resistance to out of range values:
• The test leads are incorrectly connected. • Air blowing across the TED • Measuring the resistance at other than room temperature of 70°F • Holding the TED portion of the heated and cool ventilation module in your hand
| ⇒ | If the resistance is not within the specified range, replace the ventilation heat and cool module. |
Important: The test leads must be connected in the correct polarity, otherwise higher out of range values will appear. Use the Positive Lead for the supply voltage circuit and the Negative Lead for the ground circuit.
| ⇒ | If the resistance is not within the specified range, replace the ventilation heat and cool module. |
Important: The test leads need to be connected in the correct polarity, otherwise higher out of range values will appear. Use the Positive Lead for the speed control circuit and the Negative Lead for the ground circuit.
| ⇒ | If the resistance is not within the specified range, replace the ventilation heat and cool module. |
°C | °F | Ω |
|---|---|---|
Temperature vs Resistance Values (Approximate) | ||
60° | 140° | 319.9 |
50° | 122° | 433.1 |
40° | 104° | 596.6 |
30° | 86° | 837.5 |
20° | 68° | 1200 |
10° | 50° | 1757 |
0° | 32° | 2633 |
-10° | 14° | 4047 |
-20° | -4° | 6401 |
-30° | -22° | 10,450 |
-40° | -40° | 17,670 |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for CCSM replacement, setup, and programming |
