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DTC B1673 Seat belt pre-tensioner (passenger’s side) (squib) system (shorted to squib circuit power supply)
 
 
cautionIf DTC B1673 is set in SRS-ECU, be sure to diagnose the CAN bus line.
 
 
OPERATION
Only when the frontal impact exceeding the threshold is simultaneously detected (turned ON) by the front impact sensor as well as by the analog G-sensor in SRS-ECU, the electric current is supplied from SRS-ECU to the seat belt pre-tensioner (squib).
 
 
TROUBLE JUDGMENT
The code is set when the input terminal of SRS-ECU seat belt pre-tensioner (passenger’s side) (squib) is shorted to power supply.
 
 
PROBABLE CAUSES
  • Damaged wiring harness and connector
  • Seat belt pre-tensioner (passenger’s side) (squib) harness shorted to power supply
  • Malfunction of 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 the ignition switch to the "LOCK" (OFF) position 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 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. Using scan tool (M.U.T.-IIISE), check whether the DTC is set again.
(1) Connect the negative battery terminal.
(2) After erasing the DTC memory, check the DTC again.
(3) Disconnect the negative battery terminal.
Is DTC B1673 set?
Go to Step 3.
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).
 
STEP 3. Diagnosis check by dummy resistor connection.
(1) Check that the negative battery terminal is disconnected. If the negative battery terminal is connected, disconnect it.
(2) Use the flat-tipped screwdriver to pull out the locking button of harness side connector. After releasing the lock, disconnect the seat belt pre-tensioner (passenger's side) harness side connector.
(3) Connect special tool dummy resistor (MB991865) to special tool resistor harness (MB991884).
(4) Connect the special tool resistor harness to the seat belt pre-tensioner (passenger's side) harness side connector.
(5) Connect the negative battery terminal.
(6) After erasing the DTC memory, check the DTC again.
(7) Disconnect the negative battery terminal.
Is DTC B1673 set?
Go to Step 4.
Replace the seat belt with pre-tensioner (passenger’s side) (Refer to ).
 
STEP 4. Voltage measurement at the SRS-ECU connector.
(1) Check that the negative battery terminal is disconnected. If the negative battery terminal is connected, disconnect it.
(2) Disconnect the SRS-ECU connector.
(3)
dangerTo release the SRS-ECU connector short spring in the following operations, disconnect this seat belt pre-tensioner connector, and keep the squib circuit shorted.
Use the flat-tipped screwdriver to pull out the locking button of harness side connector. After releasing the lock, disconnect the seat belt pre-tensioner (passenger's side) harness side connector.
(4)
cautionThe short spring may not be released due to the insufficient insertion. Therefore, insert the insulator for 4 mm (0.16 inch) or more.
Insert an insulator [width: 3 mm (0.12 inch), thickness: 0.5 mm (0.02 inch)] such as cable tie between the PTA+, PTA- line, and the short spring, and release the short spring.
(5) Connect the negative battery terminal.
(6) Ignition switch: ON
(7) Take the measurements below at the SRS-ECU harness side connector.
  • Voltage between PTA+, PTA- line and body ground
OK: 1 volt or less
(8) Disconnect the negative battery terminal.
Is the check result normal?
Go to Step 5.
Repair the wiring harness PTA+, PTA- line between the SRS-ECU connector and the seat belt pre-tensioner (passenger's side) connector.
 
STEP 5. Using scan tool (M.U.T.-IIISE), check whether the DTC is set again.
Is DTC B1673 set?
Replace SRS-ECU (Refer to ).
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).