B1B7D

DTC B1B78: Passenger Seat Weight Sensor (front: LH) Performance
DTC B1B7D: Passenger Seat Weight Sensor
(front: RH) Performance
DTC B1B82: Passenger Seat Weight Sensor (rear: LH) Performance
DTC B1B87: Passenger Seat Weight Sensor (rear: RH) Performance










CAUTION:
If DTC B1B78, B1B7D, B1B82 or B1B87 is set in the occupant classification-ECU, always diagnose the CAN main bus lines.

CIRCUIT OPERATION

The load data from the weight sensor is classified with the occupant classification-ECU, and its classified information is send to SRS-ECU by CAN bus line. The SRS-ECU determines the air bag deployment based on this classified information, and controls the power supply circuit to the inflator.

DTC SET CONDITIONS

This DTC is set if the weight sensor output voltage is out of the range (guideline: 1 to 3.5 V).

TROUBLESHOOTING HINTS

- The weight sensor may be defective.
- Occupant classification-ECU may be defective.
- The wiring harness or connectors may have loose, corroded, or damaged terminals, or terminals pushed back in the connector

DIAGNOSIS

Required Special Tools:

- MB991958 Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: Vehicle Communication Interface (V.C.I.)
- MB991827 M.U.T.-III USB Cable
- MB991910 M.U.T.-III Main Harness A (Vehicles with CAN communication system)

STEP 1. Using scan tool MB991958, diagnose the CAN bus line.

CAUTION:
To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.





(1)Connect scan tool MB991958. Refer to "How to connect the scan tool Reading and Clearing Diagnostic Trouble Codes."
(2)Turn the ignition switch to the "ON" position.
(3)Diagnose the CAN bus line.
(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the CAN bus line found to be normal?

YES Go to Step 2.

NO Repair the CAN bus line CAN Bus Diagnostics Chart).

STEP 2. Recheck for diagnostic trouble code.

Check again if the DTC is set.

(1)Erase the DTC.

(2)Turn the ignition switch to the "ON" position.

(3)Check if the DTC is set.

(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the DTC set?

YES Go to Step 3.
NO There is an intermittent malfunction such as poor engaged connector(s) or open circuit How to Cope With Intermittent Malfunctions).
STEP 3. Check occupant classification-ECU connector D-39-1 and weight sensor connector D-39-3, D-39-4, D-39-5 or D-39-6 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q. Is the check result normal?

YES Go to Step 4.
NO Replace the component(s) Harness Connector Inspection).
STEP 4. Check the wiring harness between occupant classification-ECU connector D-39-1 (terminal 3, 5, 7, and 9) and weight sensors D-39-3, D-39-4, D-39-5, and D-39-6 (terminal 3).

Q. Is the check result normal?

YES Go to Step 5.
NO The wiring harness may be damaged or the connector(s) may have loose, corroded or damaged terminals, or terminals pushed back in the connector. Repair the wiring harness as necessary.
STEP 5. Recheck for diagnostic trouble code.

Check again if the DTC is set to the occupant classification-ECU.

(1)Erase the DTC.

(2)Turn the ignition switch from "LOCK" (OFF) position to "ON" position.

(3)Check if DTC is set.

(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the DTC set?

YES Replace the slide adjuster (RH) Front Seat Assembly Disassembly and Assembly).
NO There is an intermittent malfunction such as poor engaged connector(s) or open circuit How to Cope With Intermittent Malfunctions).