Buick Regal: DTC B183B or B183C

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 B183B

Seat Lumbar Support Switch Signal Circuit

DTC B183C

Seat Bolster/Massage Switch Signal Circuit

For symptom byte information refer to Symptom Byte List.

Diagnostic Fault Information

1. The seat lumbar support function is inoperative.
2. The seat side bolster/massage function is inoperative.

Circuit/System Description

Ground is supplied to the seat lumbar support and the seat back side bolster switches. Each switch is also supplied with a 5 V reference and signal circuits from the seat memory control module. The reference voltage is applied to a resistive network internal to the switches. When a switch is pressed, the output of the resistive network results in a voltage drop on the signal circuit to the seat memory control module indicating the lumbar, bolster, or massage request. In response to this signal, the seat memory control module sends a LIN serial data message to the seat bolster memory control module commanding it to perform the required pneumatic movements.

Conditions for Running the DTC

• DTC B1327 must not be present.
• Battery voltage must be between 9 - 16 V.

Conditions for Setting the DTC

B183B 06

If the seat memory control module detects a short to ground or an open in the seat lumbar support switch signal circuit this DTC will set.

B183B 08

If the seat memory control module detects an invalid signal on the seat lumbar support switch signal circuit this DTC will set.

B183B 59

The seat memory control module detects a stuck lumbar support switch for a given amount of time.

B183C 06

If the seat memory control module detects a short to ground or an open in the seat bolster/massage switch signal circuit this DTC will set.

B183C 08

If the seat memory control module detects an invalid signal on the seat bolster/massage switch signal circuit this DTC will set.

B183C 59

The seat memory control module detects a stuck seat bolster or massage switch for a given amount of time.

Actions Taken When the DTC Sets

B183B 06, B183B 08, or B183B 59

• Current and history DTCs are set.
• All seat lumbar support commands and are ignored.

B183C 06, B183C 08, or B183C 59

• Current and history DTCs are set.
• All seat bolster and massage commands and are ignored.

Conditions for Clearing the DTCs

• The DTC automatically clears when the switch circuit setting the DTC is no longer active.
• A history DTC will clear once 50 consecutive fault-free ignition cycles have occurred.

Reference Information

Schematic Reference

• Driver Seat Wiring Schematics
• Passenger Seat Wiring Schematics

Connector End View Reference

Component Connector End View Index

Description and Operation

Lumbar Support Description and Operation (With Memory Seat A44/A45) or Lumbar Support Description and Operation (Without Memory Seat A44/A45)

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 DTC B183B 59 is not set as a current DTC.

• If the DTC is set current

Replace the S65 Seat Lumbar Support Switch.

• Go to next step: If the DTC is not set current

3. Verify DTC B183C 59 is not set as a current DTC.

• If the DTC is set current

Replace the S66 Seat Back Side Bolster Adjuster Switch.

• Go to next step: If the DTC is not set current

4. Verify DTC B183B 06 or B183B 08 is not set.

• If either DTC is set

Refer to Circuit/System Testing - DTC B183B Lumbar Switch Circuit Test.

• Go to next step: If either DTC is not set

5. Verify DTC B183C 06 or B183C 08 is not set.

• If either DTC is set

Refer to Circuit/System Testing - DTC B183C Seat Back Side Bolster Switch Circuit Test.

• Go to next step: If either DTC is not set

6. All OK.

Circuit/System Testing

DTC B183B Lumbar Switch Circuit Test

1. Ignition OFF, disconnect the harness connector at the appropriate seat lumbar support switch listed below. It may take up to 2 min for all vehicle systems to power down.

• S65D Seat Lumbar Support Switch - Driver
• S65P Seat Lumbar Support Switch - Passenger

2. Test for less than 10 Ω between the ground circuit terminal 1 and ground.

• If 10 Ω or greater

1. Ignition OFF.
2. Test for less than 2 Ω in the ground circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit
   • If less than 2 Ω, repair the open/high resistance in the ground connection.

• Go to next step: If less than 10 Ω

3. Ignition ON.

4. Test for 4.8 - 5.2 V between the 5 V reference circuit terminal 3 and ground.

• If less than 4.8 V

1. Ignition OFF, disconnect the X5 harness connector at the K40 Seat Memory Control Module.
2. Test for infinite resistance between the 5 V reference circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the 5 V reference circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K40 Seat Memory Control Module.

• If greater than 5.2 V

1. Ignition OFF, disconnect the X5 harness connector at the K40 Seat Memory Control Module, ignition ON.
2. Test for less than 1 V between the 5 V reference circuit and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the K40 Seat Memory Control Module.

• Go to next step: If between 4.8 - 5.2 V

5. Test for less than 1 V between the signal circuit terminal 2 and ground.

• If 1 V or greater

1. Ignition OFF, disconnect the X5 harness connector at the K40 Seat Memory Control Module, ignition ON.
2. Test for less than 1 V between the signal circuit and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the K40 Seat Memory Control Module.

• Go to next step: If less than 1 V

NOTE: With the seat lumbar support switch disconnected, DTC B183B with symptom byte 06 may already be set. However, the purpose of this test is to verify DTC B183B will set with symptom byte 08 when the signal circuit is shorted to voltage.

6. Install a 3 A fused jumper wire between the 5 V reference circuit terminal 3 and the signal circuit terminal 2.

7. Verify DTC B183B 08 is set.

• If DTC B183B 08 is not set

1. Ignition OFF, disconnect the X5 harness connector at the K40 Seat Memory Control Module.
2. Test for infinite resistance between the signal circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K40 Seat Memory Control Module.

• Go to next step: If DTC B183B 08 is set

8. Test or replace the S65 Seat Lumbar Support Switch.

DTC B183C Seat Back Side Bolster Switch Circuit Test

1. Ignition OFF, disconnect the harness connector at the seat back side bolster adjuster switch listed below. It may take up to 2 min for all vehicle systems to power down.

• S66D Seat Back Side Bolster Adjuster Switch - Driver
• S66P Seat Back Side Bolster Adjuster Switch - Passenger

2. Test for less than 10 Ω between the ground circuit terminal 1 and ground.

• If 10 Ω or greater

1. Ignition OFF.
2. Test for less than 2 Ω in the ground circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit
   • If less than 2 Ω, repair the open/high resistance in the ground connection.

• Go to next step: If less than 10 Ω

3. Ignition ON.

4. Test for 4.8 - 5.2 V between the 5 V reference circuit terminal 3 and ground.

• If less than 4.8 V

1. Ignition OFF, disconnect the X5 harness connector at the K40 Seat Memory Control Module.
2. Test for infinite resistance between the 5 V reference circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the 5 V reference circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K40 Seat Memory Control Module.

• If greater than 5.2 V

1. Ignition OFF, disconnect the X5 harness connector at the K40 Seat Memory Control Module, ignition ON.
2. Test for less than 1 V between the 5 V reference circuit and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the K40 Seat Memory Control Module.

• Go to next step: If between 4.8 - 5.2 V

5. Test for less than 1 V between the signal circuit terminal 2 and ground.

• If 1 V or greater

1. Ignition OFF, disconnect the X5 harness connector at the K40 Seat Memory Control Module, ignition ON.
2. Test for less than 1 V between the signal circuit and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the K40 Seat Memory Control Module.

• Go to next step: If less than 1 V

NOTE: With the seat back side bolster adjuster switch disconnected, DTC B183C with symptom byte 06 may already be set. However, the purpose of this test is to verify DTC B183C will set with symptom byte 08 when the signal circuit is shorted to voltage.

6. Install a 3 A fused jumper wire between the 5 V reference circuit terminal 3 and the signal circuit terminal 2.

7. Verify DTC B183C 08 is set.

• If DTC B183C 08 is not set

1. Ignition OFF, disconnect the X5 harness connector at the K40 Seat Memory Control Module.
2. Test for infinite resistance between the signal circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K40 Seat Memory Control Module.

• Go to next step: If DTC B183C 08 is set

8. Test or replace the S66 Seat Back Side Bolster Adjuster Switch.

Component Testing

Seat Lumbar Support Switch

1. Ignition OFF, disconnect the harness connector at the S65 Seat Lumbar Support Switch.

2. Test for infinite resistance between the signal terminal 2 and the ground terminal 1 with the switch in the open position.

• If less than infinite resistance

Replace the S65 Seat Lumbar Support Switch.

• Go to next step: If infinite resistance

3. Test for 252 - 308 Ω between the signal terminal 2 and the 5 V reference terminal 3.

• If not between 252 - 308 Ω

Replace the S65 Seat Lumbar Support Switch.

• Go to next step: If between 252 - 308 Ω

4. Test for 146 - 178 Ω between the signal terminal 2 and the ground terminal 1 while pressing the lumbar rearward switch.

• If not between 146 - 178 Ω

Replace the S65 Seat Lumbar Support Switch.

• Go to next step: If between 146 - 178 Ω

5. Test for 459 - 561 Ω between the signal terminal 2 and the ground terminal 1 while pressing the lumbar forward switch.

• If not between 459 - 561 Ω

Replace the S65 Seat Lumbar Support Switch.

• Go to next step: If between 459 - 561 Ω

6. Test for 1134 - 1386 Ω between the signal terminal 2 and the ground terminal 1 while pressing the lumbar down switch.

• If not between 1134 - 1386 Ω

Replace the S65 Seat Lumbar Support Switch.

• Go to next step: If between 1134 - 1386 Ω

7. Test for 3.02k - 3.7 kΩ between the signal terminal 2 and the ground terminal 1 while pressing the lumbar up switch.

• If not between 3.02k - 3.7 kΩ

Replace the S65 Seat Lumbar Support Switch.

• Go to next step: If between 3.02k - 3.7 kΩ

8. All OK.

Seat Back Side Bolster Switch

1. Ignition OFF, disconnect the harness connector at the S66 Seat Back Side Bolster Adjuster Switch.

2. Test for infinite resistance between the signal terminal 2 and the ground terminal 1 with the switch in the open position.

• If less than infinite resistance

Replace the S66 Seat Back Side Bolster Adjuster Switch.

• Go to next step: If infinite resistance

3. Test for 252 - 308 Ω between the signal terminal 2 and the 5 V reference terminal 3.

• If not between 252 - 308 Ω

Replace the S66 Seat Back Side Bolster Adjuster Switch.

• Go to next step: If between 252 - 308 Ω

4. Test for 459 - 561 Ω between the signal terminal 2 and the ground terminal 1 while pressing the seat back side bolster inflate switch.

• If not between 459 - 561 Ω

Replace the S66 Seat Back Side Bolster Adjuster Switch.

• Go to next step: If between 459 - 561 Ω

5. Test for 1134 - 1386 Ω between the signal terminal 2 and the ground terminal 1 while pressing the seat back side bolster deflate switch.

• If not between 1134 - 1386 Ω

Replace the S66 Seat Back Side Bolster Adjuster Switch.

• Go to next step: If between 1134 - 1386 Ω

6. Test for 3.02k - 3.7 kΩ between the signal terminal 2 and the ground terminal 1 while pressing the massage switch.

• If not between 3.02k - 3.7 kΩ

Replace the S66 Seat Back Side Bolster Adjuster Switch.

• Go to next step: If between 3.02k - 3.7 kΩ

7. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Driver or Passenger Seat Lumbar Control Switch Replacement
• Control Module References for K40D Seat Memory Control Module - Driver or K40P Seat Memory Control Module - Passenger replacement, programming, and setup

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