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Tahoe / Yukon Service Manual

Rear 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
5740 B+ U0247, 1 U0247, 1 — —
6740 B+ 4 4 — —
7047 Signal 2 3 3 —
7048 Low Reference — 3 — —
2294 Control 1 2 1 —
2446 Control 1 2 1 —
7053 Signal 4 5 5 —
7054 Low Reference — 5 — —
2296 Control 1 4 1 —
2457 Control 1 4 1 —
1450 Ground — U0247, 1 — —
1. Left and right rear heated seats are inoperative. 2. Left rear heated seat is inoperative 3. Degraded left rear heated seat operation 4. Right rear heated seat is inoperative 5. Degraded right rear heated seat operation

Scan Tool Data K9 Body Control Module

Data List Parameter Values Normal Operation
Seat Heating/Venting/Cooling Data Left Rear 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.
Right Rear 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 right rear and left rear heated seats switches are located within the A34 Heater and Air Conditioning Auxiliary Control. 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 A34 Heater and Air Conditioning Auxiliary Control 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 K29RV Rear Seat Heater Vent Control Module indicating the heated seat command. In response to this message, the K29RV Rear 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 K29RV Rear Seat Heater Vent Control Module controls heated seat operation for the left and right rear 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 K29RV Rear 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 left and right rear 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 left and right rear 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. Reference Information Schematic Reference Heated/Cooled Seat Schematics Connector End View Reference Master Electrical Component List Description and Operation Rear Heated Seats 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 for the heated seat system. ⇒ If DTCs are set for the heated seat system Refer to: Diagnostic Trouble Code (DTC) List - Vehicle ⇓ If no DTCs are set
  3. Verify the scan tool Left Rear Seat Heating/Venting/Cooling Mode parameter changes state when pressing the left rear heated seat switch. ⇒ If the parameter does not change Replace the A34 Heater and Air Conditioning Auxiliary Control. ⇓ If the parameter changes
  4. Verify the scan tool Right Rear Seat Heating/Venting/Cooling Mode parameter changes state when pressing the right rear heated seat switch. ⇒ If the parameter does not change Replace the A34 Heater and Air Conditioning Auxiliary Control. ⇓ If the parameter changes
  5. Verify the left and right rear heated seats operate. ⇒ If the left and right rear heated seats are inoperative Refer to Circuit/System Testing – Both Heated Seats are Inoperative ⇒ If the one heated seat is inoperative Refer to Circuit/System Testing – One Heated Seat Inoperative ⇒ If the left rear seat exhibits a degraded heated seat operation Refer to Circuit/System Testing – Degraded Heated Seat Operation Left Rear Seat ⇒ If the right rear seat exhibits a degraded heated seat operation Refer to Circuit/System Testing – Degraded Heated Seat Operation Right Rear Seat ⇓ If both rear heated seats operate
  6. A fault is currently not present and may be an intermittent condition. Circuit/System Testing Both Heated Seats are Inoperative
  1. Ignition OFF, disconnect the X1 connector at the K29RV Rear 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 5740. ⇒ If the test lamp does not illuminate and the circuit fuse is open 2.1. Test circuit 5740 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 K29RV Rear 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 6740. ⇒ If the test lamp does not illuminate and the circuit fuse is open 3.1. Test circuit 6740 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 K29RV Rear 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 2296 or circuit 2457. ⇓ 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 2294 or circuit 2446. ⇓ 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 2296 or circuit 2457. ⇓ 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 2294 or circuit 2446. ⇓ If infinite resistance
  9. Replace the K29RV Rear Seat Heater Vent Control Module. One Heated Seat is Inoperative
  1. Ignition OFF, disconnect the X1 connector at the K29RV Rear 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 6740. ⇒ If the test lamp does not illuminate and the circuit fuse is open 2.1. Test the circuit 6740 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 K29RV Rear Seat Heater Vent Control Module. ⇓ If the test lamp illuminates
  3. Ignition OFF, connect the X1 connector at the K29RV Rear Seat Heater Vent Control Module. Disconnect the connector at the appropriate component: Left rear heated seat inoperative = E14F Seat Heating Element - Left Rear Cushion Right rear heated seat inoperative = E14H Seat Heating Element - Right Rear Cushion
  4. Ignition ON.
  1. Test for 4.8–5.2 V between the appropriate signal circuit terminal and ground: E14F Seat Heating Element - Left Rear Cushion = Terminal 2 E14H Seat Heating Element - Right Rear Cushion = Terminal 2 ⇒ If less than 4.8 V 5.1. Test the appropriate circuit for a short to ground: E14F Seat Heating Element - Left Rear Cushion = Circuit 7047 E14H Seat Heating Element - Right Rear Cushion = Circuit 7053 ⇒ 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: E14F Seat Heating Element - Left Rear Cushion = Circuit 7047 E14H Seat Heating Element - Right Rear Cushion = Circuit 7053 ⇒ 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 K29RV Rear Seat Heater Vent Control Module. ⇒ If greater than 5.2 V 5.1. Test the appropriate circuit for a short to voltage: E14F Seat Heating Element - Left Rear Cushion = Circuit 7047 E14H Seat Heating Element - Right Rear Cushion = Circuit 7053 ⇒ 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 K29RV Rear Seat Heater Vent Control Module. ⇓ If between 4.8–5.2 V
  2. Connect a test lamp between the appropriate control circuit terminals: E14F Seat Heating Element - Left Rear Cushion = Terminal 1 and terminal 4 E14H Seat Heating Element - Right Rear Cushion = Terminal 1 and terminal 4
  3. Engine running.
  1. Verify the test lamp turns ON after pressing the appropriate heated seat switch. ⇒ If the test lamp is always OFF 8.1. Test the appropriate circuits for an open/high resistance: E14F Seat Heating Element - Left Rear Cushion = Circuit 2294 and circuit 2446 E14H Seat Heating Element - Right Rear Cushion = Circuit 2296 and circuit 2457 ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found 8.2. Replace the K29RV Rear Seat Heater Vent Control Module. ⇓ If the test lamp turns ON
  1. Replace the appropriate component: E14F Seat Heating Element - Left Rear Cushion E14H Seat Heating Element - Right Rear Cushion Degraded Heated Seat Operation Left Rear Seat
  1. Ignition OFF, disconnect the connector at E14F Seat Heating Element - Left Rear Cushion. It may take up to 2 min for all vehicle systems to power down.
  2. Test for less than 40 Ω between the low reference circuit terminal 3 and ground. ⇒ If 40 Ω or greater 2.1. Test circuit 7048 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 K29RV Rear Seat Heater Vent Control Module. ⇓ If less than 40 Ω
  3. Ignition ON.
  4. Test for 4.8–5.2 V between the signal circuit terminal 2 and ground. ⇒ If less than 4.8 V 4.1. Test circuit 7047 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 4.2. Test circuit 7047 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 4.3. Replace the K29RV Rear Seat Heater Vent Control Module. ⇒ If greater than 5.2 V 4.1. Test circuit 7047 for a short to voltage. ⇒ 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 K29RV Rear Seat Heater Vent Control Module. ⇓ If between 4.8–5.2 V
  5. Ignition OFF, connect the connector at the E14F Seat Heating Element - Left Rear Cushion. Disconnect the X2 connector at the K29RV Rear Seat Heater Vent Control Module.
  6. Test for 500 Ω–300 kΩ between the signal circuit terminal 6 and the low reference circuit terminal 1. ⇒ If not between 500 Ω–300 kΩ 6.1. Replace the E14F Seat Heating Element - Left Rear Cushion. ⇓ If between 500 Ω–300 kΩ
  7. Replace the K29RV Rear Seat Heater Vent Control Module. Degraded Heated Seat Operation Right Rear Seat
  1. Ignition OFF, disconnect the connector at E14H Seat Heating Element - Right Rear Cushion. It may take up to 2 min for all vehicle systems to power down.
  2. Test for less than 40 Ω between the low reference circuit terminal 3 and ground. ⇒ If 40 Ω or greater 2.1. Test circuit 7054 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 K29RV Rear Seat Heater Vent Control Module. ⇓ If less than 40 Ω
  3. Ignition ON.
  4. Test for 4.8–5.2 V between the signal circuit terminal 2 and ground. ⇒ If less than 4.8 V 4.1. Test circuit 7053 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 4.2. Test circuit 7053 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 4.3. Replace the K29RV Rear Seat Heater Vent Control Module. ⇒ If greater than 5.2 V 4.1. Test circuit 7053 for a short to voltage. ⇒ 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 K29RV Rear Seat Heater Vent Control Module. ⇓ If between 4.8–5.2 V
  5. Ignition OFF, connect the connector at the E14H Seat Heating Element - Right Rear Cushion. Disconnect the X2 connector at the K29RV Rear Seat Heater Vent Control Module.
  6. Test for 500 Ω–300 kΩ between the signal circuit terminal 6 and the low reference circuit terminal 1. ⇒ If not between 500 Ω–300 kΩ 6.1. Replace the E14HF Seat Heating Element - Right Rear Cushion. ⇓ If between 500 Ω–300 kΩ
  7. Replace the K29RV Rear Seat Heater Vent Control Module. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Control Module References for K29RV Rear Seat Heater Vent Control Module replacement, programming, and setup