Front Heated Seat Malfunction

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. Diagnostic Fault Information

	Circuit Number	Circuit Function	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performan	ce
	6640	B+	U0208, 1	U0208, 1	—	—
	6140	B+	6	6	—	—
	2425	Signal	2	5	5	—
	2080	Low Reference	—	5	—	—
	2079	Signal	2	5	5	—
	2077	Control	1	2, 3, 4	1	—
	2078	Control	1	2, 3, 4	1	—
	2432	Control	1	2, 3, 4	1	—
	2436	Signal	6	9	9	—
	2482	Low Reference	—	9	—	—
	2434	Signal	6	9	9	—
	2435	Low Reference	—	9	—	—
	2479	Control	1	6, 7, 8	1	—
	2480	Control	1	6, 7, 8	1	—
	2481	Control	1	6, 7, 8	1	—
	1250	Ground	—	U0208, 1	—	—

1. Driver and passenger heated seats are inoperative.

Circuit Number	Circuit Function	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performan
2. Driver heated seat is inoperative 3. Driver seat back heat function is inoperative 4. Driver seat cushion heat function is inoperative 5. Degraded driver heated seat operation 6. Passenger heated seat is inoperative 7. Passenger seat back heat function is inoperative 8. Passenger seat cushion heat function is inoperative 9. Degraded passenger heated seat operation

Scan Tool Data K9 Body Control Module

Data List	Parameter	Values	Normal Operation
Seat Heating/Venting/Cooling Data	Driver Seat Heating/Venting/C Mode	Off / Seat Back and Cushion ooling Heating / Seat Venting/Cooling	This parameter indicates the type of Heated/Vented Seat function being applied as commanded by the BCM.
	Passenger Seat Heating/Venting/C Mode	Off / Seat Back and Cushion ooling Heating / Seat Venting/Cooling	This parameter indicates the type of Heated/Vented Seat function being applied as commanded by the BCM.

Circuit/System Description The driver and passenger heated seats switches are located within the A26 Heater and Air Conditioning User Interface Control - Front. To operate the heated seats the engine must be running. When a heated seat switch is pressed, a serial data message is sent from the A26 Heater and Air Conditioning User Interface Control - Front to the K9 Body Control Module (BCM) indicating the heated seat command. The BCM serves as the heated seat system master to determine the requested operating mode. The BCM then sends a LIN bus serial data message to the K29FV Front Seat Heater Vent Control Module indicating the heated seat command. In response to this message, the K29FV Front Seat Heater Vent Control Module attempts to drive the appropriate seat heating elements per the BCM command. The BCM also controls the seat temperature and mode indicators, via the serial data line, used to provide the operator with feedback as to the operating status of the system. The K29FV Front Seat Heater Vent Control Module controls heated seat operation for the driver and passenger seats. When active, power is applied to the seat cushion and back heater elements through a common pulse width modulated (PWM) voltage supply control circuit. Each individual heater element is switched to ground by the module through a common low side drive control circuit. The seat back and cushion temperature sensors (thermistors) are packaged with the seat heating elements located just under the seat covers. The K29FV Front Seat Heater Vent Control Module supplies each temperature sensor with a 5 V reference signal circuit and a low reference circuit. The module monitors the voltage from the signal circuit to determine the temperature of the seat. The temperature sensor varies in resistance based on the temperature of the heating element causing the signal voltage to change. Once the module senses the seat reached the set temperature, it will then begin regulate the current flow through the heater elements in order to maintain the desired seat temperature based on the feedback voltage from the sensor. Diagnostic Aids A short to ground or B+ in either the heating element voltage control circuit or ground control circuit will cause both the driver and front passenger heated seats to be inoperative. An open in either the voltage control circuit or ground control circuit between the module and the splice will cause the seat cushion and seat back the heated seat function to be inoperative for that seat. A short to ground on either the seat cushion or seat back temperature sensor signal circuit will cause the heated seat function to be inoperative for that seat. An open in either the voltage control circuit or ground control circuit between the splice and the heating element will cause just that one heating element to be inoperative. The following faults will cause a degraded heated seat operation for both the seat back and seat cushion. – An open or a short to voltage on either the seat cushion or seat back temperature sensor signal circuit. – An open in either the seat cushion or seat back temperature sensor low reference circuit. – A fault in either the seat cushion or seat back temperature sensor. A broken wire in a heating element may cause a degraded heated seat operation for that particular heating element. When inactive the seat heating control module connects the heating element low side outputs to a common reference point internal to the module which is biased to approximately 3.5 V. The module uses this biased voltage in order to check the high side and low side control circuits for a short to battery or ground before enabling the driver and passenger seat heating elements. With both the seat cushion and seat back heater elements disconnected, if the high side output of the module is measured it will display a low current 12 V bleed off voltage. This bleed off voltage does not have a meaningful diagnostic purpose. With one or both of the heater elements connected you would just see the 3.5 V biased voltage from this circuit. If the heated seats are on high, the temperature level may automatically be lowered after approximately 30 min of operation. Heated seat operation may be inhibited if the vehicle was in an accident. To restore operation of the heated seats, it may be necessary to reset crash data in the supplemental restraint module. This is done by performing the reset disable request after crash event detected under configuration/reset functions in GDS 2. Reference Information Schematic Reference Heated/Cooled Seat Schematics Connector End View Reference Master Electrical Component List Description and Operation Heated/Vented Seat Description and Operation Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs Scan Tool Reference Control Module References for scan tool information Circuit/System Verification

1. Engine ON.
2. Verify that no DTCs are set. ⇒ If DTCs are set Refer to: Diagnostic Trouble Code (DTC) List - Vehicle ⇓ If no DTCs are set
3. Verify the scan tool Driver Seat Heating/Venting/Cooling Mode parameter changes state when pressing the driver heated seat switch. ⇒ If the parameter does not change Replace the A26 Heater and Air Conditioning User Interface Control - Front. ⇓ If the parameter changes
4. Verify the scan tool Passenger Seat Heating/Venting/Cooling Mode parameter changes state when pressing the passenger heated seat switch. ⇒ If the parameter does not change Replace the A26 Heater and Air Conditioning User Interface Control - Front. ⇓ If the parameter changes
5. Verify the driver and passenger heated seats operate. ⇒ If the driver and front passenger heated seats are inoperative Refer to Circuit/System Testing – Both Heated Seats are Inoperative ⇒ If the seat cushion and back heating elements are inoperative of one seat Refer to Circuit/System Testing – One Heated Seat Inoperative ⇒ If just one of the heating elements is inoperative Refer to Circuit/System Testing – One Heating Element is Inoperative. ⇒ If the driver seat exhibits a degraded heated seat operation Refer to Circuit/System Testing – Degraded Heated Seat Operation Driver Seat ⇒ If the passenger seat exhibits a degraded heated seat operation Refer to Circuit/System Testing – Degraded Heated Seat Operation Passenger Seat ⇓ If both heated seats operate
6. A fault is currently not present and may be an intermittent condition. Circuit/System Testing Both Heated Seats are Inoperative

Note

Circuit/System Verification must be performed before proceeding with Circuit/System Testing.

1. Ignition OFF, disconnect the X1 connector at the K29FV Front Seat Heater Vent Control Module, ignition ON.
2. Verify a test lamp illuminates between the B+ circuit terminal 10 and ground. ⇒ If the test lamp does not illuminate and the circuit fuse is good 2.1. Repair the open/high resistance on circuit 6640. ⇒ If the test lamp does not illuminate and the circuit fuse is open 2.1. Test circuit 6640 for a short to ground. ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found 2.2. Replace the K29FV Front Seat Heater Vent Control Module. ⇓ If the test lamp illuminates
3. Verify a test lamp illuminates between the B+ circuit terminal 7 and ground. ⇒ If the test lamp does not illuminate and the circuit fuse is good 3.1. Repair the open/high resistance on circuit 6140. ⇒ If the test lamp does not illuminate and the circuit fuse is open 3.1. Test circuit 6140 for a short to ground. ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found 3.2. Replace the K29FV Front Seat Heater Vent Control Module. ⇓ If the test lamp illuminates
4. Test for less than 1 V between control circuit terminal 2 and ground. ⇒ If 1 V or greater 4.1. Repair the short to voltage on circuit 2479, circuit 2480, or circuit 2481. ⇓ If less than 1 V
5. Test for less than 1 V between control circuit terminal 6 and ground. ⇒ If 1 V or greater 5.1. Repair the short to voltage on circuit 2077, circuit 2078, or circuit 2432. ⇓ If less than 1 V
6. Ignition OFF.
7. Test for infinite resistance between control circuit terminal 2 and ground. ⇒ If less than infinite resistance 7.1. Repair the short to ground on circuit 2479, circuit 2480, or circuit 2481. ⇓ If infinite resistance
8. Test for infinite resistance between control circuit terminal 6 and ground. ⇒ If less than infinite resistance 8.1. Repair the short to ground on circuit 2077, circuit 2078, or circuit 2432. ⇓ If infinite resistance
9. Replace the K29FV Front Seat Heater Vent Control Module. One Heated Seat is Inoperative

Note

Circuit/System Verification must be performed before proceeding with Circuit/System Testing

1. Ignition OFF, disconnect the X1 connector at the K29FV Front Seat Heater Vent Control Module, ignition ON.
2. Verify a test lamp illuminates between the B+ circuit terminal 7 and ground. ⇒ If the test lamp does not illuminate and the circuit fuse is good 2.1. Repair the open/high resistance on the circuit 6140. ⇒ If the test lamp does not illuminate and the circuit fuse is open 2.1. Test the circuit 6140 for a short to ground. ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found 2.2. Replace the K29FV Front Seat Heater Vent Control Module. ⇓ If the test lamp illuminates
3. Ignition OFF, connect the X1 connector at the K29FV Front Seat Heater Vent Control Module. Disconnect the connector at the appropriate components: Driver heated seat inoperative = E14A Seat Heating Element – Driver Back and the E14B Seat Heating Element – Driver Cushion Passenger heated seat inoperative = E14C Seat Heating Element – Passenger Back and the E14D Seat Heating Element – Passenger Cushion
4. Ignition ON.

Note

When performing this test ensure that you are testing from the correct terminal. Testing from the incorrect terminal will cause a misdiagnosis of the circuit. Three of the four terminals in this connector will not only display a voltage reading but a different voltage reading.

5. Test for 4.8–5.2 V between the appropriate signal circuit terminal and ground: E14B Seat Heating Element – Driver Cushion = Terminal 2 E14D Seat Heating Element – Passenger Cushion = Terminal 2 ⇒ If less than 4.8 V 5.1. Test the appropriate circuit for a short to ground: E14B Seat Heating Element – Driver Cushion = Circuit 2079 E14D Seat Heating Element – Passenger Cushion = Circuit 2434 ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found 5.2. Test the appropriate circuit for an open/high resistance: E14B Seat Heating Element – Driver Cushion = Circuit 2079 E14D Seat Heating Element – Passenger Cushion = Circuit 2434 ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found 5.3. Replace the K29FV Front Seat Heater Vent Control Module. ⇒ If greater than 5.2 V 5.1. Test the appropriate circuit for a short to voltage: E14B Seat Heating Element – Driver Cushion = Circuit 2079 E14D Seat Heating Element – Passenger Cushion = Circuit 2434 ⇒ If a short to voltage is found, repair the fault on the circuit. ⇓ If a short to voltage is not found 5.2. Replace the K29FV Front Seat Heater Vent Control Module. ⇓ If between 4.8–5.2 V

Note

When performing this test ensure that you are testing from the correct terminal. Testing from the incorrect terminal will cause a misdiagnosis of the circuit. Three of the four terminals in this connector will not only display a voltage reading but a different voltage reading.

6. Test for 4.8–5.2 V between the appropriate signal circuit terminal and ground: E14A Seat Heating Element – Driver Back = Terminal 2 E14C Seat Heating Element – Passenger Back = Terminal 2 ⇒ If less than 4.8 V 6.1. Test the appropriate circuit for a short to ground: E14A Seat Heating Element – Driver Back = Circuit 2425 E14C Seat Heating Element – Passenger Back = Circuit 2436 ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found 6.2. Test the appropriate circuit for an open/high resistance: E14A Seat Heating Element – Driver Back = Circuit 2425 E14C Seat Heating Element – Passenger Back = Circuit 2436 ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found 6.3. Replace the K29FV Front Seat Heater Vent Control Module. ⇒ If greater than 5.2 V 6.1. Test the appropriate circuit for a short to voltage: E14A Seat Heating Element – Driver Back = Circuit 2425 E14C Seat Heating Element – Passenger Back = Circuit 2436 ⇒ If a short to voltage is found, repair the fault on the circuit. ⇓ If a short to voltage is not found 6.2. Replace the K29FV Front Seat Heater Vent Control Module. ⇓ If between 4.8–5.2 V
7. Connect a test lamp between the appropriate control circuit terminals: E14A Seat Heating Element – Driver Back = Terminal 1 and terminal 4 E14C Seat Heating Element – Passenger Back = Terminal 1 and terminal 4
8. Engine running.

Note

The test lamp should turn ON for approximately 10 s after the heated seat is commanded ON.

9. Verify the test lamp turns ON after pressing the appropriate heated seat switch. ⇒ If the test lamp is always OFF 9.1. Test the appropriate circuits for an open/high resistance: E14A Seat Heating Element – Driver Back = Circuit 2432 and circuit 2078 E14C Seat Heating Element – Passenger Back = Circuit 2481 and circuit 2480 ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found 9.2. Replace the K29FV Front Seat Heater Vent Control Module. ⇓ If the test lamp turns ON
10. Connect the connector at the appropriate component: E14B Seat Heating Element – Driver Cushion E14D Seat Heating Element – Passenger Cushion
11. Verify the test lamp turns ON after pressing the appropriate heated seat switch. ⇒ If the test lamp is always OFF

Note

Because of the type of material used in the heater element, a reliable resistance value is unavailable for a component test. 11.1. Replace the appropriate component: E14B Seat Heating Element – Driver Cushion E14D Seat Heating Element – Passenger Cushion ⇓ If the test lamp turns ON

Note

Because of the type of material used in the heater element, a reliable resistance value is unavailable for a component test.

12. Replace the appropriate component: E14A Seat Heating Element – Driver Back E14C Seat Heating Element – Passenger Back One Heating Element is Inoperative

Note

Circuit/System Verification must be performed before proceeding with Circuit/System Testing.

1. Ignition OFF, disconnect the connector at the appropriate E14 Seat Heating Element.
2. Connect a test lamp between control circuit terminal 1 and control circuit terminal 4, engine ON.

Note

The test lamp should turn ON for approximately 10 s after the heated seat is commanded ON.

3. Verify the test lamp turns ON after pressing the heated seat switch. ⇒ If the test lamp is always OFF 3.1. Test the appropriate circuits for an open/high resistance: E14A Seat Heating Element – Driver Back = Circuit 2432 and Circuit 2078 E14B Seat Heating Element – Driver Cushion = Circuit 2077 and Circuit 2078 E14C Seat Heating Element – Passenger Back = Circuit 2479 and Circuit 2480 E14D Seat Heating Element – Passenger Cushion = Circuit 2481 and Circuit 2480 ⇓ If the test lamp turns ON

Note

Because of the type of material used in the heater element, a reliable resistance value is unavailable for a component test.

4. Replace the appropriate E14 Seat heating Element. Degraded Heated Seat Operation Driver Seat

Note

Circuit/System Verification must be performed before proceeding with Circuit/System Testing

1. Ignition OFF, disconnect the connector at each component listed below. It may take up to 2 min for all vehicle systems to power down. E14A Seat Heating Element – Driver Back E14B Seat Heating Element – Driver Cushion
2. Test for less than 40 Ω between each low reference circuit terminal listed below and ground, one at a time. E14A Seat Heating Element – Driver Back = Terminal 3 E14B Seat Heating Element – Driver Cushion = Terminal 3 ⇒ If 40 Ω or greater 2.1. Test circuit 2080 for an open/high resistance. ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found 2.2. Replace the K29FV Front Seat Heater Vent Control Module. ⇓ If less than 40 Ω
3. Ignition ON.
4. Test for 4.8–5.2 V between each signal circuit terminal listed below and ground, one at a time. E14A Seat Heating Element – Driver Back = Terminal 2 E14B Seat Heating Element – Driver Cushion = Terminal 2 ⇒ If less than 4.8 V 4.1. Test the appropriate circuit for a short to ground: E14A Seat Heating Element – Driver Back = Circuit 2425 E14B Seat Heating Element – Driver Cushion = Circuit 2079 ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found 4.2. Test the appropriate circuit for an open/high resistance: E14A Seat Heating Element – Driver Back = Circuit 2425 E14B Seat Heating Element – Driver Cushion = Circuit 2079 ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found 4.3. Replace the K29FV Front Seat Heater Vent Control Module. ⇒ If greater than 5.2 V 4.1. Test the appropriate circuit for a short to voltage: E14A Seat Heating Element – Driver Back = Circuit 2425 E14B Seat Heating Element – Driver Cushion = Circuit 2079 ⇒ If a short to voltage is found, repair the fault on the circuit. ⇓ If a short to voltage is not found 4.2. Replace the K29FV Front Seat Heater Vent Control Module. ⇓ If between 4.8–5.2 V
5. Ignition OFF, connect the connector at the E14B Seat Heating Element – Driver Cushion and the E14A Seat Heating Element – Driver Back. Disconnect the X2 connector at the K29FV Front Seat Heater Vent Control Module.
6. Test for 500 Ω–300 kΩ between the signal circuit and the low reference circuit terminals listed below, one at a time. Terminal 3 and terminal 1 at K29FV Front Seat Heater Vent Control Module Terminal 6 and terminal 1 at K29FV Front Seat Heater Vent Control Module ⇒ If not between 500 Ω–300 kΩ 6.1. Replace the appropriate component: Terminal 3 and terminal 1 at K29FV Front Seat Heater Vent Control Module = E14A  Seat Heating Element – Driver Back Terminal 6 and terminal 1 at K29FV Front Seat Heater Vent Control Module = E14B  Seat Heating Element – Driver Cushion ⇓ If between 500 Ω–300 kΩ
7. Replace the K29FV Front Seat Heater Vent Control Module. Degraded Heated Seat Operation Passenger Seat

Note

Circuit/System Verification must be performed before proceeding with Circuit/System Testing

1. Ignition OFF, disconnect the connector at each component listed below. It may take up to 2 min for all vehicle systems to power down. E14C Seat Heating Element – Passenger Back E14D Seat Heating Element – Passenger Cushion
2. Test for less than 40 Ω between each low reference circuit terminal listed below and ground, one at a time. E14C Seat Heating Element – Passenger Back = Terminal 3 E14D Seat Heating Element – Passenger Cushion = Terminal 3 ⇒ If 40 Ω or greater 2.1. Test the appropriate circuit for an open/high resistance: E14C Seat Heating Element – Passenger Back = Circuit 2482 E14D Seat Heating Element – Passenger Cushion = Circuit 2435 ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found 2.2. Replace the K29FV Front Seat Heater Vent Control Module. ⇓ If less than 40 Ω
3. Ignition ON.
4. Test for 4.8–5.2 V between each signal circuit terminal listed below and ground, one at a time. E14C Seat Heating Element – Passenger Back = Terminal 2 E14D Seat Heating Element – Passenger Cushion = Terminal 2 ⇒ If less than 4.8 V 4.1. Test the appropriate circuit for a short to ground: E14C Seat Heating Element – Passenger Back = Circuit 2436 E14D Seat Heating Element – Passenger Cushion = Circuit 2434 ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found 4.2. Test the appropriate circuit for an open/high resistance: E14C Seat Heating Element – Passenger Back = Circuit 2436 E14D Seat Heating Element – Passenger Cushion = Circuit 2434 ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found 4.3. Replace the K29FV Front Seat Heater Vent Control Module. ⇒ If greater than 5.2 V 4.1. Test the appropriate circuit for a short to voltage: E14C Seat Heating Element – Passenger Back = Circuit 2436 E14D Seat Heating Element – Passenger Cushion = Circuit 2434 ⇒ If a short to voltage is found, repair the fault on the circuit. ⇓ If a short to voltage is not found 4.2. Replace the K29FV Front Seat Heater Vent Control Module. ⇓ If between 4.8–5.2 V
5. Ignition OFF, connect the connector at the E14D Seat Heating Element – Passenger Cushion and the E14C Seat Heating Element – Passenger Back. Disconnect the X2 connector at the K29FV Front Seat Heater Vent Control Module.
6. Test for 500 Ω–300 kΩ between the signal circuit and the low reference circuit terminals listed below, one at a time. Terminal 4 and terminal 12 at K29FV Front Seat Heater Vent Control Module Terminal 5 and terminal 2 at K29FV Front Seat Heater Vent Control Module ⇒ If not between 500 Ω–300 kΩ 6.1. Replace the appropriate component: Terminal 4 and terminal 12 at K29FV Front Seat Heater Vent Control Module = E14C  Seat Heating Element – Passenger Back Terminal 5 and terminal 2 at K29FV Front Seat Heater Vent Control Module = E14D  Seat Heating Element – Passenger Cushion ⇓ If between 500 Ω–300 kΩ
7. Replace the K29FV Front Seat Heater Vent Control Module. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Front Seat Back Heater Replacement Front Seat Cushion Heater Replacement Control Module References for K29FV Front Seat Heater Vent Control Module replacement, programming, and setup