For 1990-2009 cars

### Test Description

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

1. This step determines if the heated seat system is totally inoperative.

2. This step determines if the seat is completely inoperative, or if just one of the 2 seat cushions is inoperative.

3. This step determines which part of the seat is inoperative, the seat cushion or seat back.

4. This step tests the integrity of the heated seat switch signal from the memory seat module. This signal is a momentary 35 millisecond one- shot pulse signal that is displayed by a momentary change in the volt voltmeter when the switch is pressed. In order to accurately recognize the change in voltage, the voltmeter reading should be stable before performing this test.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Driver Seat Schematics and Passenger Seat Schematics Connector End View Reference: Component Connector End Views DEFINITION: This test assumes that Load Shed Level 1 or 2 Heated Seats is not Enabled.
1 | Did you review the heated seat operation and perform the necessary inspection? | -- | Go to Step 2 | Go to Symptoms - Seats
2 | Verify that the heated seat inoperative complaint is present. Does the heated seat system operate as described in the system description and operation? | -- | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3
3 | Are both the driver and front passenger heated seats inoperative? | -- | Go to Step 6 | Go to Step 4
4 | Are both the seat cushion and seat back inoperative? | -- | Go to Step 10 | Go to Step 5
5 | Is the seat cushion inoperative? | -- | Go to Step 14 | Go to Step 15
6 |

1. Turn OFF the ignition.
2. Disconnect the climate control seat module connector C1.
3. Turn ON the ignition, with the engine OFF.
4. Measure the voltage from the battery positive voltage circuit of the climate control seat module to a good ground.

Does the voltage measure within the specified range?

10-15 V

Go to Step 7

Go to Step 31

7 | Measure the voltage from the battery positive voltage circuit of the climate control seat module to the ground circuit of the climate control seat module. Does the voltage measure within the specified range? | 10-15 V | Go to Step 8 | Go to Step 32
8 | Measure the voltage from the ignition 3 voltage circuit of the climate control seat module to a good ground. Does the voltage measure within the specified range? | 10-15 V | Go to Step 9 | Go to Step 33
9 | Note: If the resistance is measured with the seat still warm, the resistance may vary outside of the specified range since the thermistor resistance varies with temperature. Measure the resistance between the signal circuit of the temperature sensor signal circuit and the temperature sensor low reference circuit of the module connector.

Does the resistance measure within the specified range?

850 Ω - 1150 K Ω

Go to Step 26

Go to Step 34

10 |

1. Install a scan tool.
2. Turn ON the ignition, with the engine OFF.
3. With a scan tool, observe the appropriate Heated Seat Sw. parameter in the Climate Control Panel Non-HVAC Data list.
4. Press the suspected heated seat switch.

Does the scan tool display Pressed?

--

Go to Step 11

Go to Step 30

11 |

1. Measure the voltage from the appropriate pulse width modulation (PWM) serial data signal circuit from the memory seat module (MSM) to a good ground
2. PRESS the heated seat switch.

Does the measured voltage momentarily change state?

--

Go to Step 13

Go to Step 12

12 |

1. Turn OFF the ignition.
2. Disconnect the MSM connector C4.
3. Turn ON the ignition, with the engine OFF.
4. Measure the voltage from the appropriate PWM serial data signal circuit of the MSM connector to a good ground.

Does the voltage measure within the specified range?

4.50-5.50 V

Go to Step 29

Go to Step 22

13 |

1. Disconnect the climate control seat module connectors C1 and C2.
2. Measure the resistance between the heated seat element supply voltage circuit of the module connector and the ground circuit of the module connector.

Is the resistance value less than the specified value?

5 Ω

Go to Step 16

Go to Step 17

14 |

1. Disconnect the seat cushion heating element connector.
2. Measure the resistance between the element supply voltage circuit and the ground circuit of the seat cushion heating element.

Is the resistance value less than the specified value?

5 Ω

Go to Step 18

Go to Step 27

15 |

1. Disconnect the seat back heating element connector.
2. Measure the resistance between the element supply voltage circuit and the ground circuit of the seat back heating element.

Is the resistance value less than the specified value?

5 Ω

Go to Step 19

Go to Step 28

16 | Note: If the resistance is measured with the seat still warm, the resistance may vary outside of the specified range since the thermistor resistance varies with temperature. Measure the resistance between the signal circuit of the temperature sensor and the low reference circuit of the temperature sensor.

Does the resistance measure within the specified range?

850 Ω - 1150 K Ω

Go to Step 20

Go to Step 24

17 | Test the element supply voltage circuit between the climate control seat module and the seat heating elements for an open. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 41 | Go to Step 35
18 | Test the element supply voltage circuit of the seat cushion heating element for an open. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 41 | Go to Step 35
19 | Test the element supply voltage circuit of the seat back heating element for an open. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 41 | Go to Step 35
20 | Test the element supply voltage circuit between the climate control seat module and the seat heating elements for a short to ground. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 41 | Go to Step 21
21 | Test the temperature sensor signal circuit between the climate control seat module and the temperature sensor for a short to ground. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 41 | Go to Step 26
22 | Test the appropriate PWM serial data signal circuit between the MSM and the climate control seat module for a short to ground or an open. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 41 | Go to Step 23
23 | Test the appropriate PWM serial data signal circuit between the MSM and the climate control seat module for a short to voltage or an open. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 41 | Go to Step 26
24 | Test the temperature sensor signal circuit between the climate control seat module and the temperature sensor for an open and a short to voltage. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 41 | Go to Step 25
25 | Test the temperature sensor low reference circuit between the climate control seat module and the temperature sensor for an open. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 41 | Go to Step 27
26 | Inspect for poor connections at the harness connector of the climate control seat module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs. Did you find and correct the condition? | -- | Go to Step 41 | Go to Step 36
27 | Inspect for poor connections at the harness connector of the seat cushion heating element and temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs. Did you find and correct the condition? | -- | Go to Step 41 | Go to Step 37
28 | Inspect for poor connections at the harness connector of the seat back heating element. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs. Did you find and correct the condition? | -- | Go to Step 41 | Go to Step 38
29 | Inspect for poor connections at the harness connector of the MSM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs. Did you find and correct the condition? | -- | Go to Step 41 | Go to Step 39
30 | Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 41 | Go to Step 40
31 | Repair the short to ground or open in the battery positive voltage circuit of the climate control seat module. Refer to Wiring Repairs. Is the trouble corrected? | -- | Go to Step 41 | --
32 | Repair the open in the ground circuit of the climate control seat module. Refer to Wiring Repairs. Is the trouble corrected? | -- | Go to Step 41 | --
33 | Repair the short to ground or open in the ignition 3 voltage circuit of the climate control seat module. Refer to Wiring Repairs. Is the trouble corrected? | -- | Go to Step 41 | --
34 | Repair the open in the low reference circuit of the seat temperature sensor. Refer to Wiring Repairs. Is the trouble corrected? | -- | Go to Step 41 | --
35 | Repair the open in the ground circuit of the seat heating elements. Refer to Wiring Repairs. Is the trouble corrected? | -- | Go to Step 41 | --
36 | Replace the climate control seat module. Refer to Control Module References for replacement, setup, and programming. Have you finished the replacement? | -- | Go to Step 41 | --
37 | Replace the seat cushion heating element/temperature sensor. Have you finished the replacement? | -- | Go to Step 41 | --
38 | Replace the seat back heating element. Refer to Driver or Passenger Seat Back Ventilation Heating and Cooling Blower Replacement. Have you finished the replacement? | -- | Go to Step 41 | --
39 | Replace the MSM. Refer to Control Module References for replacement, setup, and programming. Have you finished the replacement? | -- | Go to Step 41 | --
40 | Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming. Have you finished the replacement? | -- | Go to Step 41 | --
41 | Operate the system to verify the repair. Did you correct the condition? | -- | System OK | Go to Step 2