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Seat Belt Indicator Circuit Malfunction - Rear



Seat Belt Indicator Circuit Malfunction - Rear

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/System Description
All three rear seat belt switches are 2-wire switch wired to the inflatable restraint sensing and diagnostic module (SDM) using a signal circuit and a low reference circuit. When the seat belt is unbuckled the switch is closed, and when the seat belt is buckled the switch is open. The SDM sends the status of the rear seat belt via serial data to the driver information center. After receiving the message, the driver information center controls the illumination of the driver seat belt indicator.

Reference Information

Schematic Reference
Seat Belt Schematics [1][2]Electrical Diagrams

Connector End View Reference
Component Connector End Views

Description and Operation
Seat Belt System Description and Operation 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

Diagnostic Aids
1. The mechanical stop in the buckle may prevent latching but the switch in the buckle may momentarily open and the SDM would interpret this as an occupant in the rear seat position and that the buckle was attempting to latch.
2. If a rear occupant attempts to latch the seat belt into the wrong buckle, the indicator may illuminate and the system assumes there is an occupant not buckled in that seat position.
3. An unseated connector can appear as a buckled seat belt connection.

Circuit/System Verification
1. Verify that all connectors are fully seated.
2. With the scan tool monitor the 2nd Row Seat Belt Status parameter while buckling and unbuckling the seat belt. The parameter should display Buckled and Unbuckled when buckling and unbuckling the seat belt.
3. Replace the P9 driver information center.

Circuit/System Testing

NOTE: When removing connectors inspect for damage or corrosion. Damage or corrosion in the following requires repair or replacement of the affected component/connector.
- B88 Seat belt switch
- Seat belt switch harness connector
- K36 SDM
- SDM wiring harness connector

1. Ignition OFF.
2. Disconnect the harness connector at the B88 seat belt switch.
3. Test for less than 5 ohm between the ground circuit terminal B and ground.
3.1. Disconnect the harness connector at the K36 SDM.
3.2. Test for less than 2 ohm in each control circuit end to end.

4. Ignition ON.
5. Verify the scan tool 2nd Row Seat Belt Status parameter displays Buckled.
5.1. Disconnect the harness connector at the K36 SDM.
5.2. Test for infinite resistance between the seat belt switch signal circuit terminal A and ground.

6. Install a 3 A fused jumper wire between the circuit terminal A and the ground circuit terminal B.
7. Verify the scan tool 2nd Row Seat Belt Status parameter displays Unbuckled.
7.1. Disconnect the harness connector at the K36 SDM.
7.2. Ignition ON.
7.3. Test for less than 1 V between the signal circuit and ground.
7.4. Test for less than 2 ohm in each circuit end to end.

8. Replace the B88 seat belt switch.

Component Testing
1. Ignition OFF.
2. Disconnect the harness connector at the B88 seat belt switch.
3. B88 seat belt switch in the open position.
4. Test for infinite resistance between the signal circuit terminal A and the ground terminal B at the B88 seat belt switch.
5. Replace the B88 seat belt switch.
6. B88 seat belt switch in the closed position.
7. Test for less than 1 ohm between the signal circuit terminal A and the ground terminal B at the B88 seat belt switch.
8. Replace the B88 seat belt switch.
9. All OK.

Repair Instructions
- Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
- Rear Seat Buckle Side Belt Replacement (With 40 Percent Seat) Rear Seat Buckle Side Belt Replacement (With 60 Percent Seat)
- Rear Seat Center Buckle Side Belt Replacement
- Control Module References for SDM and driver information center setup and programming
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