Test Description
The numbers below refer to the step numbers on the diagnostic table.
- 2: Lack of communication may be due to a partial malfunction of the class 2 serial data circuit or due to a total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.
- 5: The presence of DTCs which begin with "U" indicate some other module is not communicating. The specified procedure will compile all the available information before tests are performed.
| Step | Action | Yes | No |
|---|---|---|---|
| 1 | Install a scan tool. Does the scan tool power up? | Go to Step 2 | Go to Scan Tool Does Not Power Up in Data Link Communications |
| 2 | Attempt to establish communication with the driver seat module. Does the scan tool communicate with the driver seat module? | Go to Step 3 | Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications |
| 3 | IMPORTANT: The engine may start during the following step. Turn OFF the engine as soon as you have observed the Crank power mode. Access the Class 2 Power Mode in the Diagnostic Circuit Check on the scan tool. Rotate the ignition switch through all positions while observing the ignition switch power mode parameter. Does the ignition switch parameter reading match the ignition switch position for all switch positions? | Go to Step 4 | Go to Power Mode Mismatch in Body Control System |
| 4 | Select the display DTCs function on the scan tool for the driver seat module. Does the scan tool display any DTCs? | Go to Step 5 | Go to Symptoms - Seats |
| 5 | Does the scan tool display any DTC that begins with a "U"? | Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications | Go to Step 6 |
| 6 | Does the scan tool display B1000? | Go to Diagnostic Trouble Code (DTC) List in Body Control System | Go to Diagnostic Trouble Code (DTC) List |
| IMPORTANT |
|---|
| The engine may start during the following step. Turn OFF the engine as soon as you have observed the Crank power mode. |
Diagnostic System Check - Power Seat Systems
Lumbar Support System Operation
Battery voltage is supplied to the lumbar switch through the power seat circuit breaker. While the switches are in an inactive state the switch contacts are closed to the switch ground circuit. When a switch is pressed to an active state the switch contact is closed to the battery voltage supply circuit. Each motor is controlled by the lumbar switch through 2 motor control circuits. The motors are bidirectional and the direction of motor rotation is determined by which of the motor control circuits is switched to battery voltage while the other remains grounded.
Memory Lumbar Support System Operation
The driver seat module (DSM) controls the lumbar motor but will not store memory lumbar positions. The DSM supplies the lumbar adjuster switch assembly with a battery positive reference voltage. When a switch is pressed to an active state the switch contact is closed to the reference voltage circuit. Battery voltage on a switch signal circuit indicates to the seat module the switch status is active. Each seat adjuster motor is controlled by the seat module through 2 motor control circuits. While the seat adjuster motors are in an inactive state the motor control circuits are closed to ground circuit contacts within the seat module. The seat module operates the seat adjuster motors by switching one of a motor's control circuits to battery voltage. The seat adjuster motors are bidirectional and the direction of adjuster motor rotation is determined by which of the adjuster motor control circuits is switched to battery voltage while the other remains grounded.
Heated Seats System Operation
The driver and front passenger seats are heated using electric heater elements located in the seat cushions and seat backs. The driver seat module (DSM) controls the voltage supply and the ground circuits to the driver and passenger seat heater elements. When a heated seat function is commanded active, the seat module will switch battery voltage to the heater element supply circuits and ground is provided through low side drive control circuits. During heated seat operation both the seat back and cushion heater elements are supplied battery voltage. The seat module grounds the appropriate control circuits for driver or passenger heated seat operation, and opens or closes the active control circuits, as necessary, in order to maintain the desired seat temperature. The heated seat switch and a heat sensor located in the seat cushion are connected in series and provide a single input to the DSM. A 5-volt reference voltage is supplied to the heated seat switch from the DSM. When the heated seat switch is in the high or low positions voltage is supplied through one of the internal resistors to the switch signal circuit. The heated seat switch signal circuit is grounded through the seat heat sensor which is a temperature sensitive variable resistor. The heated seat switch signal circuit input to the DSM is spliced from the circuit between the switch and the heat sensor, where the voltage level is determined by the resistance of both components. The passenger heated seat switch must be enabled through the seat belt switch in order for heated seat operation to occur.
The memory seat system consists of the following components
- Power seat switch
- Seat horizontal motor
- Seat front vertical motor
- Seat rear vertical motor
- Seat recliner motor
- Driver seat module
- Memory seat switch
Battery voltage is supplied to the driver seat module (DSM) through the power seat circuit breaker. The DSM supplies the seat adjuster switch assembly with a battery positive reference voltage. When a seat adjuster switch is pressed to an active state the switch contact is closed to the reference voltage circuit. Battery voltage on a switch signal circuit indicates to the DSM the switch status is active. Each seat adjuster motor is controlled by the DSM through 2 motor control circuits. While the seat adjuster motors are in an inactive state the motor control circuits are closed to ground circuit contacts within the DSM. The DSM operates the seat adjuster motors by switching one of a motor's control circuits to battery voltage. The seat adjuster motors are bidirectional and the direction of adjuster motor rotation is determined by which of the adjuster motor control circuits is switched to battery voltage while the other remains grounded.
Memory Set/Recall Operation
The driver seat adjuster motors are equipped with internal potentiometer type position sensors. The adjuster motor position sensors are monitored by the DSM and are used to determine the seat position when storing or recalling memory settings. The front vertical, rear vertical, horizontal, and recline position sensors are supplied with common 5-volt reference and ground circuits from the DSM. The position sensor signal circuits are supplied 5 volts through resistors then monitored within the DSM. The signal voltages monitored by the DSM range from 0.39-4.58 volts and are determined by the wiper locations on the resistors within the position sensors. The position sensor signal circuit voltage levels are used by the DSM to determine the seat position when storing or recalling memory seat position settings.
The memory switch assembly provides inputs to the DSM. Battery voltage is supplied to the memory switch assembly from the seat module. When a memory 1, 2, or EXIT switch is pressed, the switch contacts close the appropriate switch signal circuit to the battery voltage supply circuit within the memory switch assembly. When the seat module receives active switch signals from the memory switch assembly, the appropriate seat adjuster motors are operated, as necessary, until the position sensor signal voltages match the stored values.
Memory seat recall operation, while the ignition is ON, is allowed only with the transmission selector lever in the PARK position. The transmission selector lever position data is provided to the DSM by a message through the class 2 Serial Data circuit.