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Tahoe / Yukon Service Manual

Power Folding Seat Malfunction (3rd Row)

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
7840 B+ U1132, 1 U1132, 1 U1132, 1 —
240 B+ U1121, 1, 2 U1121, 1, 2 U1121, 1, 2 —
2854 Serial Data U1132, 1 U1132, 1 U1132, 1 —
2694 Signal B1B29:23 1 B1B29:24 —
2695 Signal B1B2A:23 1 B1B2A:24 —
2696 Signal B1B2B:23 1 B1B2B:24 —
2697 Signal B1B2C:23 1 B1B2C:24 —
4217 Control B14E2 11 B14E2 13 B14E2 12 —
4218 Control B14E3 11 B14E3 13 B14E3 12 —
4221 Control B14E6 11 B14E6 13 B14E6 12 —
4222 Control B14E7 11 B14E7 13 B14E7 12 —
4213 Signal B14E0:11 B14E0:15 B14E0:15 —
4214 Signal B14E1:11 B14E1:15 B14E1:15 —
8920 Control B1B25 11 B1B25 13 B1B25 12 —
8921 Control B1B26 11 B1B26 13 B1B26 12 —
8922 Control B1B27 11 B1B27 13 B1B27 12 —
8923 Control B1B28 11 B1B28 13 B1B28 12 —
Circuit Number Circuit Function Short to Ground Open/High Resistance Short to Voltage Signal Performan
5474 Low Reference — B14E0:15, B14E1:15 — —
1850 Ground U1132, U1121, 1 U1132, U1121, 1 U1132, U1121, 1 —
1. 3rd Row Power Folding Seat Malfunction

Circuit/System Description The power folding third row seat system consists of folding seat switches, a control module, a seat back release actuator, a hall-effect position sensor, and the folding seat motor. The third row folding seat switches are located on the D-pillar. Voltage to the switches is supplied through the park enable relay while in a de-energized state. The park enable relay is controlled by the body control module (BCM) through a high side drive control circuit and will be de-energized whenever the ignition is in the accessory or run positions and the transmission is in park. Battery voltage is supplied to the folding seat control module through a 30 A fuse located in the rear body fuse block. When a folding seat switch is pressed, battery voltage is applied through the switch contacts and the signal circuit to the folding seat control module indicating the folding seat request. In response to this signal, the module applies a PWM voltage through the seat back release actuator control circuit energizing the actuator. With the actuator energized and the seat back released, the control module applies battery voltage and ground through the folding seat motor control circuits to the motor. The motor runs to either move the seat back cushion to the folded or unfolded seat position. The control module supplies the hall-effect sensor with a low reference and a signal circuit. The module monitors the voltage from the signal circuit in order to detect a seat stall condition. If the module does not detect seat movement within 400ms, it will cease folding seat operation. The 3rd row folding seat switches are located on the D-pillar of the rear cargo area. Each side of the 60/40 split seat has a pair of fold and unfold normally open, high assertion, momentary switches designed to keep them from being simultaneously pressed. The overhead console has two switches that are used to fold the 3rd row seat. The left switch operates the left portion of the seat and the right switch operates the right portion of the seat. When the left LED is illuminated it means that the 3rd row power folding seat module sees one of the unlatch switches as active and the left seatback in the 3rd row is not in fully unfolded seated position. When the right LED is illuminated it means that the 3rd row power folding seat module sees one of the latch/unlatch switches is active and the right seatback in the 3rd row is not in fully unfolded seated position. Each switch contact is connected to an individual discrete input of the folding seat control module which provides a pull down to ground on these signal circuits. When a folding seat switch is pressed battery voltage is applied through the switch contacts and the signal circuit to the folding seat control module. The module then commands the folding seat to move in response to the switch signal. Reference Information Schematic Reference Rear Seat Schematics Connector End View Reference Master Electrical Component List Description and Operation Power Seats System 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/Vehicle in Service Mode.
  2. Verify DTC U1121 or U1132 are not set. ⇒ If DTC U1121 or U1132 are set Refer to Diagnostic Trouble Code (DTC) List - Vehicle. ⇓ If DTC U1121 or U1132 are not set
  3. Verify that no DTCs related to the 3rd Row Power Folding Seats are set. ⇒ If any DTCs are set Refer to: Diagnostic Trouble Code (DTC) List - Vehicle ⇓ If no DTCs are set
  4. Operate all 3rd row power seat functions in the Up/Down.
  5. Verify that no DTCs related to the 3rd Row Power Folding Seats are set. ⇒ If any DTCs are set Refer to: Diagnostic Trouble Code (DTC) List - Vehicle ⇓ If no DTCs are set
  6. Operate all 3rd row power seat to the folded and fully unfolded positions.
  7. Verify that the appropriate red LED’s in the A103 Roof Console turn On and Off. ⇒ If the LED’s in the Roof Console do not turn On and OFF Refer to Circuit/System Testing ⇓ If the LED’s in the Roof Console do not turn On and OFF
  8. A fault is currently not present and may be an intermittent condition. Circuit/System Testing
  9. Ignition/Vehicle OFF, disconnect the appropriate B377 3rd Row Seat Back Latch Unlatched Switch listed below. B377LL 3rd Row Seat Back Latch Unlatched Switch – Left Seat Left Side B377LR 3rd Row Seat Back Latch Unlatched Switch – Left Seat Right Side B377RL 3rd Row Seat Back Latch Unlatched Switch – Right Seat Left Side B377RR 3rd Row Seat Back Latch Unlatched Switch – Right Seat Right Side
  10. Verify a test lamp illuminates between low reference circuit terminal 2 and B+. ⇒ If the test lamp does not illuminate 2.1. Test circuit 5474 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 K169 Folding 3rd Row Seat Module. ⇓ If the test lamp illuminates
  11. Ignition/Vehicle in Service Mode.
  12. Test for 4.8–5.2 Volts between signal circuit terminal 1 and ground. ⇒ If less than 4.8 V 4.1. Test the appropriate circuit for a short to ground. Circuit 2694 Circuit 2695 Circuit 2696 Circuit 2697 ⇒ 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. Circuit 2694 Circuit 2695 Circuit 2696 Circuit 2697 ⇒ 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 K169 Folding 3rd Row Seat Module. ⇒ If greater than 5.2 V 4.1. Test the appropriate circuit for a short to voltage. Circuit 2694 Circuit 2695 Circuit 2696 Circuit 2697 ⇒ 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 K169 Folding 3rd Row Seat Module. ⇓ If between 4.8–5.2 V
  13. Replace the appropriate B377 3rd Row Seat Back Latch Unlatched Switch listed below: B377LL 3rd Row Seat Back Latch Unlatched Switch – Left Seat Left Side B377LR 3rd Row Seat Back Latch Unlatched Switch – Left Seat Right Side B377RL 3rd Row Seat Back Latch Unlatched Switch – Right Seat Left Side B377RR 3rd Row Seat Back Latch Unlatched Switch – Right Seat Right Side Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Control Module References for K169 Folding 3rd Row Seat Module replacement, programming and setup. 3rd Row Seat Riser Replacement for the appropriate B377 3rd Row Seat Back Latch