Skip to content
Tahoe / Yukon Service Manual

DTC B12CC, B1338, B1339, or B133A

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. DTC Descriptors DTC B12CC Driver Seat Heating Temperature Sensor Signal DTC B1338 Driver Seat Back Heating Temperature Sensor Signal DTC B1339 Passenger Seat Heating Temperature Sensor Signal DTC B133A Passenger Seat Back Heating Temperature Sensor Signal Symptom Byte Information: Symptom Byte List Diagnostic Fault Information

Circuit Number Circuit Function Short to Ground Open/High Resistance Short to Voltage Signal Performan
6640 B+ U0208 U0208 — —
6140 B+ 1 1 — —
2425 Signal B1338:16 B1338:17 B1338:17 —
2080 Low Reference — B1338:17, B12CC:17 — —
2079 Signal B12CC:16 B12CC:17 B12CC:17 —
2436 Signal B133A:16 B133A:17 B133A:17 —
2482 Low Reference — B133A:17 — —
2434 Signal B1339:16 B1339:17 B1339:17 —
2435 Low Reference — B1339:17 — —
1250 Ground — U0208 — —
1. Passenger heated seat is inoperative

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. Conditions for Running the DTC Engine ON. Heated Seat System ON. Conditions for Setting the DTC B12CC:16, B1338:16, B1339:16, B133A:16 The front seat heater control module detects low voltage on a thermistor signal circuit. B12CC:17, B1338:17, B1339:17, B133A:17 The front seat heater control module detects high voltage on a thermistor signal circuit. Action Taken When the DTC Sets The seat heater control module will disable all heated seat functions. Conditions for Clearing the DTC The DTC clears when the diagnostic runs and passes. The history DTC will clear after 40 consecutive fault-free ignition cycles have occurred. Diagnostic Aids 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. 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. 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. Ignition ON.
  2. Verify that no other DTCs are set for the heated seat system, besides B12CC, B1338, B1339, or B133A. ⇒ If any other DTCs are set for the heated seat system Refer to: Diagnostic Trouble Code (DTC) List - Vehicle ⇓ If no other DTCs are set
  3. Clear the DTCs.
  4. Verify DTC B12CC, B1338, B1339, or B133A is not set. ⇒ If DTC B12CC or B1338 is set Refer to Circuit/System Testing — B12CC or B1338 ⇒ If DTC B1339 or B133A is set Refer to Circuit/System Testing — B1339 or B133A ⇓ If no DTCs are set
  5. A fault is currently not present and may be an intermittent condition. Circuit/System Testing B12CC or B1338
  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. Terminal 3 at E14A Seat Heating Element – Driver Back Terminal 3 at E14B Seat Heating Element – Driver Cushion ⇒ 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. Terminal 2 at E14A Seat Heating Element – Driver Back Terminal 2 at E14B Seat Heating Element – Driver Cushion ⇒ If less than 4.8 V 4.1. Test the appropriate circuit for a short to ground: Terminal 2 at E14A Seat Heating Element – Driver Back = Circuit 2425 Terminal 2 at 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: Terminal 2 at E14A Seat Heating Element – Driver Back = Circuit 2425 Terminal 2 at 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: Terminal 2 at E14A Seat Heating Element – Driver Back = Circuit 2425 Terminal 2 at 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 connectors 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. B1339 or B133A
  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. Terminal 3 at E14C Seat Heating Element – Passenger Back Terminal 3 at E14D Seat Heating Element – Passenger Cushion ⇒ If 40 Ω or greater 2.1. Test the appropriate circuit for an open/high resistance: Terminal 3 at E14C Seat Heating Element – Passenger Back = Circuit 2482 Terminal 3 at 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. Terminal 2 at E14C Seat Heating Element – Passenger Back Terminal 2 at E14D Seat Heating Element – Passenger Cushion ⇒ If less than 4.8 V 4.1. Test the appropriate circuit for a short to ground: Terminal 2 at E14C Seat Heating Element – Passenger Back = Circuit 2436 Terminal 2 at 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: Terminal 2 at E14C Seat Heating Element – Passenger Back = Circuit 2436 Terminal 2 at 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: Terminal 2 at E14C Seat Heating Element – Passenger Back = Circuit 2436 Terminal 2 at 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 connectors 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.