B1537

The contents of this article reflect the changes called out by TSB 04-52b-001





DTC B1537: Seat belt switch (RH) circuit open (for COM terminal)

Passenger's Seat Belt Switch Circuit:

CAUTION:
If DTC B1530, B1531, B1532, B1533, B1534, B1535, B1536, B1537, B1538 or B1539 are set in the combination meter, always diagnose the CAN 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
DTC is set when the resistance between input terminals of the seat belt switch in the SRS-ECU is without the standard value.




Cause of trouble in each DTC is as shown in the table.

TROUBLESHOOTING HINTS
- Malfunction of the seat belt switch
- Damaged wiring harnesses or connectors
- Malfunction of the SRS-ECU

DIAGNOSIS

Required Special Tools:
- MB991222: Probe
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: Vehicle Communication Interface (V.C.I.)
- MB991827: MUT-III USB Cable
- MB991910: MUT-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 Diagnostic Trouble Codes
2. Connect scan tool MB991958 to the data link connector.
3. Turn the ignition switch to the "ON" position.
4. Diagnose the CAN bus line.
5. Turn the ignition switch to the "LOCK" (OFF) position.

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

YES: Go to Step 3.

NO: Repair the CAN bus line (Refer to Diagnosis). Component Tests and General Diagnostics Then go to Step 2.




STEP 2. Recheck for diagnostic trouble code.
Check again if the DTC is set.

1. Erase the DTC.
2. Turn the ignition switch to "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 (Refer to How to Cope with Intermittent Malfunction).
















STEP 3. Check the passenger's seat belt switch.







Disconnect passenger's seat belt switch connector D-29. Then check continuity between the switch terminals.

Q: Is passenger's seat belt switch in good condition?

YES: Go to Step 4.

NO: Replace inner seat belt. (Refer to Front Seat Belt.)

STEP 4. Check the passenger's seat belt switch circuit D-29. Measure the resistance at SRS-ECU connector C-120.




1. Disconnect passenger's seat belt switch connector D-29.




2. Install the passenger's seat belt to the seat belt switch.




3. Disconnect SRS-ECU connector C-120 and measure at the harness side (rear side).







4. Measure the resistance between terminal 52 and terminal 51.
Resistance should be 820 ± 82 Ohms




5. Mesure the resistance between terminal 52, 51 and body ground.
It should be open circuit.




6. Measure the resistance between terminal 65 and terminal 65 and terminal 51.
Resistanve should be less than 2 ohms.




7. Remove the passenger's seat belt from the seat belt switch.




8. Disconnect SRS-ECU connector C-120 and measure at the harness side (rear side).




9. Measure the resistance between terminal 65 and terminal 51.
Resistance should be 820 ± 82 Ohms




10. Measure the resistance between terminal 65 and terminal 51 and body ground.
It should be open circuit.




11. Measure the resistance between terminal 52 and terminal 51.
Resistance should be less than 2 Ohms

Q: Does the resistance meet the value above?

YES: Erase the diagnostic trouble code memory, and check the diagnostic trouble code. If DTC B1530, B1531, B1532, B1533, B1534, B1535, B1536, B1537, B1538 or B1539 are set, replace the SRS-ECU. Then go to Step 6.

NO: Go to Step 5.







STEP 5. Check the harness wires between SRS-ECU connector C-120 (terminal No.52, 65 and 51) and passenger's seat belt switch connector D-29 (terminal No.1, 2 and 3).

Q: Are harness wires between SRS-ECU connector C-120 (terminal No.52, 65 and 51) and passenger's seat belt switch connector D-29 (terminal No.1, 2 and 3) in good condition?

YES: Go to Step 6.

NO: Replace the harness wires between SRS-ECU connector C-120 and passenger's seat belt switch connector D-29. Then go to Step 6.




STEP 6. 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 DTC B1530, B1531, B1532, B1533, B1534, B1535, B1536, B1537, B1538 or B1539 set?

YES: Return to Step 1.

NO: The procedure is complete.