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 seat module. 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
Battery voltage to the seat module must be within 7-16 volts.
Conditions for Setting the DTC
| • | The heated seat sensor signal circuit voltage to the seat module is greater than 4.94 volts for 30 seconds or more. |
| • | The heated seat sensor signal circuit voltage to the seat module is less than 0.07 volts for 30 seconds or more. |
| • | The heated seat sensor signal circuit input to the seat module indicates that the desired seat temperature has not been reached within 34 minutes after activation. |
Action Taken When the DTC Sets
The heated seat with a current status DTC will be disabled.
Conditions for Clearing the DTC
| • | The DTC will be stored as a history code when the fault is no longer present. |
| • | A history DTC will be cleared after completing 100 consecutive ignition cycles, or by using the scan tool clearing DTCs feature. |
Diagnostic Aids
If the DTC is only found in history, the fault may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Step | Action | Values | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Driver Seat Schematics , 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 in Vehicle DTC Information | ||||||
2 |
Does the scan tool indicate that the seat heat sensor value is within the specified range? | 0.07-4.94 | Go to Step 3 | Go to Step 4 | ||||||
3 | Is the seat heat sensor value reducing as the seat back temperature rises? | -- | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 6 | ||||||
4 | Disconnect the seat back element 4-way connector. Is the seat heat sensor value greater than the specified value? | 4.5 V | Go to Step 5 | Go to Step 7 | ||||||
5 | Connect a fused jumper wire between the heat sensor signal and low reference circuit terminals in the seat back element 4-way harness connector. Is the seat heat sensor value greater than the specified value? | 0.5 | Go to Step 8 | Go to Step 11 | ||||||
6 |
Does the test lamp illuminate? | -- | Go to Step 11 | Go to Step 10 | ||||||
7 | Test the heated seat sensor signal circuit for a short to ground. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 12 | ||||||
8 | Test the heated seat sensor signal circuit for one of the following conditions:
Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 9 | ||||||
9 | Test the heated seat sensor low reference circuit for an open or high resistance. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 12 | ||||||
10 | Test the seat back element supply and control circuits for an open or high resistance. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 12 | ||||||
11 | Inspect for poor connections at the seat back element 4-way connector. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 13 | ||||||
12 | Inspect for poor connections at the seat control module. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 14 | ||||||
13 | Replace the seat back heater element. Refer to Front Seat Back Cushion Cover and Cushion Pad Replacement . Is the repair complete? | -- | Go to Step 15 | -- | ||||||
14 | Replace the seat control module. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Is the repair complete? | -- | Go to Step 15 | -- | ||||||
15 |
Does the DTC reset? | -- | Go to Step 2 | System OK | ||||||
