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DTC B1B7A: Passenger Seat Weight Sensor (power supply side) Short-circuited or Open (front: LH)
DTC B1B7F: Passenger Seat Weight Sensor (power supply side) Short-circuited or Open (front: RH)
DTC B1B84: Passenger Seat Weight Sensor (power supply side) Short-circuited or Open (rear: LH)
DTC B1B89: Passenger Seat Weight Sensor (power supply side) Short-circuited or Open (rear: RH)
 
 
cautionIf DTC B1B7A, B1B7F, B1B84 or B1B89 is stored 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 stored if the weight sensor wire are short-circuited to the power supply.
  • This DTC is stored if the weight sensor wire are open circuit
 
 
TROUBLESHOOTING HINTS
  • Damaged wiring harnesses or connectors
  • Short to the power supply in the weight sensor harness
  • Open circuit in the weight sensor harness
  • Malfunction of the weight sensor
  • Malfunction of the occupant classification-ECU
 
 
DIAGNOSIS
STEP 1. Using scan tool MB991958, diagnose the CAN bus line.
cautionTo 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 ."
(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.
Is the CAN bus line found to be normal?
Go to Step 2.
Repair the CAN bus line (Refer to GROUP 54C, Diagnosis ).
 
STEP 2. Recheck for diagnostic trouble code.
Check again if the DTC is stored.
(1) Erase the DTC.
(2) Turn the ignition switch to the "ON" position.
(3) Check if the DTC is stored.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is the DTCs stored?
Go to Step 3.
There is an intermittent malfunction such as poor engaged connector(s) or open circuit (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).
 
STEP 3. Measure the voltage at occupant classification-ECU connector D-48-1.
(1) Disconnect the connector D-48-1.
(2) Disconnect weight sensor connector D-48-3, D-48-4, D-48-5 or D-48-6.
(3) Turn the ignition switch to the "ON" position.
(4) Measure the voltage between terminals 1, 3, 5, 7, 9 and body ground.Voltage should measure 1 volt or less.
Is the measured voltage within the specified range?
Go to Step 4.
Repair the wiring harness between occupant classification-ECU connector D-48-1 terminals 3, 5, 9, 7 and weight sensor connector D-48-3, 4, 5, 6 terminals 3 (signal line) or occupant classification-ECU connector D-48-1 terminals 1 and weight sensor connector D-48-3 terminals 2 (power supply line). Then go to Step 4.
 
STEP 4. Check the harness open circuit between occupant classification-ECU connector D-48-1 and weight sensor connector D-48-3, D-48-4, D-48-5 or D-48-6.
(1) Disconnect occupant classification-ECU connector D-48-1 and weight sensor connector D-48-3, D-48-4, D-48-5 or D-48-6.
(2) Check for continuity between the following terminals.
It should be less than 2 ohms.
  • Occupant classification-ECU connector D-48-1 (terminal No.3) and the weight sensor connector D-48-3 (terminal No.3)
  • Occupant classification-ECU connector D-48-1 (terminal No.5) and the weight sensor connector D-48-4 (terminal No.3)
  • Occupant classification-ECU connector D-48-1 (terminal No.7) and the weight sensor connector D-48-6 (terminal No.3)
  • Occupant classification-ECU connector D-48-1 (terminal No.9) and the weight sensor connector D-48-5 (terminal No.3)
  • Occupant classification-ECU connector D-48-1 (terminal No.1) and the weight sensor connector D-48-3, D-48-4, D-48-5 and D-48-6 (terminal No.2)
  • Occupant classification-ECU connector D-48-1 (terminal No.12) and weight sensor connector D-48-3, D-48-4, D-48-5 and D-48-6 (terminal No.1)
Does continuity exist?
Go to Step 5.
Repair the harness wires between occupant classification-ECU connector D-48-1 and weight sensor connector D-48-3, D-48-4, D-48-5 and D-48-6. Then go to Step 5.
 
STEP 5. Recheck for diagnostic trouble code.
Check again if the DTC is stored.
(1) Erase the DTC.
(2) Turn the ignition switch to the "ON" position.
(3) Check if the DTC is stored.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is DTC B1B7A, B1B7F, B1B84 or B1B89 stored?
Replace the passenger seat cushion frame assembly (Refer to GROUP 52A, Front Seat Assembly ).
There is an intermittent malfunction such as poor engaged connector(s) or open circuit (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).