GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2007 🢒 Sierra Classic - 4WD 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC B2435 or B2440

Circuit Description

The driver seat module (DSM) relies on inputs from thermistors located in the driver and passenger seat backs to control heated seat temperatures. The thermistors are 2 wire sensors supplied with a 5-volt referenced signal circuit and low reference circuit from the DSM. Resistance through the thermistors varies with temperature causing the heated seat sensor signal circuit voltage levels to decrease as the seat back temperatures rise.

DTC Descriptors

This diagnostic procedure supports the following DTCs:

    • DTC B2435 Driver Seat Back Heater Sensor Circuit
    • DTC B2440 Passenger Seat Back Heater Sensor Circuit

Conditions for Running the DTC
    • The system voltage must be between 9-16 volts.
    • The heated seat is in an active state.

Conditions for Setting the DTC
    • The heated seat sensor signal circuit voltage to the DSM is greater than 4.94 volts for 30 seconds or more.
    • The heated seat sensor signal circuit voltage to the DSM is less than 0.078 volts for 30 seconds or more.
    • The heated seat sensor signal circuit input to the DSM indicates that the desired seat temperature has not been reached within 30 minutes after activation.

Action Taken When the DTC Sets
    • The heated seat with a current status DTC will be disabled.
    • When the fault is no longer present a history status DTC will be stored, and heated seat operation will be restored.

Conditions for Clearing the DTC
    • The DTC will be current for as long as the fault is present.
    • When the fault is no longer present the DTC will be a history status code.
    • The history DTC will be cleared after 100 error free ignition cycles, or by using the scan tool clearing DTCs feature.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Tests for the proper operation of the circuit in the high voltage range.

    2.

  2. Tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens upon performing this test, the signal circuit has a short to voltage.

Step

Action

Values

Yes

No

Schematic Reference: Driver Seat Schematics and Passenger Seat Schematics

Connector End View Reference: Power Seat Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2
  1. Install a scan tool.
  2. Start the engine.
  3. Turn the heated seat ON.
  4. With a scan tool, observe the Heated Seat Sensor parameter in the data list for the driver seat module (DSM).

Does the scan tool indicate that the Heated Seat Sensor parameter is within the specified range?

0.078-4.94 V

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the heated seat back 4-way connector.
  3. Start the engine.
  4. Turn the heated seat ON.
  5. With a scan tool, observe the Heated Seat Sensor parameter.

Is the Heated Seat Sensor parameter greater than the specified value?

4.5 V

Go to Step 4

Go to Step 5

4

  1. Turn OFF the ignition.
  2. Connect a 3-ampere fused jumper wire between the signal circuit of the heated seat sensor and the low reference circuit of the heated seat sensor.
  3. Start the engine.
  4. Turn the heated seat ON.
  5. With a scan tool, observe the Heated Seat Sensor parameter.

Is the Heated Seat Sensor parameter less than the specified value?

0.5 V

Go to Step 8

Go to Step 6

5

Test the signal circuit of the heated seat sensor for a short to ground. Refer to Circuit Testing and to Wiring Repairs.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 9

6

Test the signal circuit of the heated seat sensor for one of the following conditions:

    • A short to voltage
    • A high resistance
    • An open

Refer to Circuit Testing and to Wiring Repairs.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 7

7

Test the low reference circuit of the heated seat sensor for one of the following conditions:

    • A high resistance
    • An open

Refer to Circuit Testing and to Wiring Repairs.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 9

8

Inspect for poor connections at the harness connector of the heated seat sensor. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 10

9

Inspect for poor connections at the harness connectors of the DSM. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 11

10

Replace the seat back heater element. Refer to Driver or Passenger Seat Back Cushion Heater Replacement .

Did you complete the replacement?

--

Go to Step 12

--

11

Replace the DSM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 12

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12
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC.

Does the DTC reset?

--

Go to Step 2

System OK