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DTC B1538: Seat Belt Switch (Passenger’s side) Circuit (Ground Side) Shorted
 
 
cautionIf DTC B1538 are set in the SRS-ECU, always diagnose the CAN main bus lines.
 
 
CIRCUIT OPERATION
The SRS-ECU determines whether the seat belt is fastened or not according to the connection location of the seat belt switch in the seat buckle.
 
 
DTC SET CONDITIONS
The DTC is set when the seat belt switch output current is not within the specified range.
 
 
TROUBLESHOOTING HINTS
  • Malfunction of the seat belt switch (passenger’s side)
  • Damaged wiring harnesses or connectors
  • Malfunction of the SRS-ECU
 
 
DIAGNOSIS
STEP 1. Using scan tool (M.U.T.-IIISE), diagnose the CAN bus line.
(1)
cautionTo prevent damage to scan tool (M.U.T.-IIISE), always turn off the power supply mode of the electric motor switch before connecting or disconnecting scan tool (M.U.T.-IIISE).
Connect scan tool (M.U.T.-IIISE). Refer to "How to connect the scan tool ."
(2) Turn on the power supply mode of the electric motor switch.
(3) Diagnose the CAN bus line.
(4) Turn off the power supply mode of the electric motor switch.
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 DTC.
Check again if the DTC is set.
(1) Erase the DTC.
(2) Turn on the power supply mode of the electric motor switch.
(3) Check if the DTC is set.
(4) Turn off the power supply mode of the electric motor switch.
Is the DTC set?
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. Seat belt switch (passenger’s side) check.
Refer to GROUP 52A, Front Seat Belt
Is the check result normal?
Go to Step 4.
Replace the seat belt switch (passenger’s side) (Refer to GROUP 52A, Front Seat Belt ).
 
STEP 4. Check the harness short circuit between seat belt switch (passenger’s side) connector and the SRS-ECU connector.
(1) Disconnect the negative battery terminal.
(2) Disconnect the seat belt switch (passenger’s side) connector.
(3) While pushing the part "A" indicated in the figure of the harness side connector, turn the lock lever to the direction of the arrow to release the lock lever, and disconnect the SRS-ECU connector.
(4) Measure the resistance between PBS-, PBSO line and body ground.
It should be an open circuit.
Is the check result normal?
Go to Step 5.
Repair the harness wires PBS-, PBSO line between SRS-ECU connector and the seat belt switch (passenger’s side) connector.
 
STEP 5. Recheck for DTC.
Check again if the DTC is set.
(1) Erase the DTC.
(2) Turn on the power supply mode of the electric motor switch.
(3) Check if the DTC is set.
(4) Turn off the power supply mode of the electric motor switch.
Is DTC B1538 set?
Replace the SRS-ECU (Refer to ).
The procedure is complete.