B1B79

DTC B1B79: Passenger Seat Weight Sensor (ground side) Short-circuited (front: LH)
DTC B1B7E: Passenger Seat Weight Sensor (ground side) Short-circuited (front: RH)
DTC B1B83: Passenger Seat Weight Sensor (ground side) Short-circuited (rear: LH)
DTC B1B88: Passenger Seat Weight Sensor
(ground side) Short-circuited (rear: RH)









CAUTION:
If DTC B1B79, B1B7E, B1B83 or B1B88 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 wire is short-circuited to ground.

TROUBLESHOOTING HINTS

- Disengaged wire harnesses or connector
- Short to the ground in the weight sensor harness
- Malfunction of the weight sensor
- Malfunction of the occupant classification-ECU

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. Measure the resistance at occupant classification-ECU connector D-39-1.

(1)Disconnect the connector D-39-1.

(2)Disconnect weight sensor connector D-39-3, D-39-4, D-39-5 or D-39-6.





(3)Check for continuity between D-39-1 harness side connector terminals 1, 3, 5, 7, 9 and body ground.
It should be open circuit.

Q. Is it open circuit?

YES Go to Step 4.

NO Repair the wiring harness between occupant classification-ECU connector D-39-1 terminals 3, 5, 9, 7 and weight sensor connector D-39-3, 4, 5, 6 terminals 3 (signal line) or occupant classification-ECU connector D-39-1 terminals 1 and weight sensor connector D-39-3 terminals 2 (power supply line). Then go to Step 4.

STEP 4. 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 DTCs B1B79, B1B7E, B1B83, B1B88 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).