DTC B1858: SW Connection: Diagnosis

Required Special Tools 

• MB991223: Wiring harness set
• MB992006: Extra fine probe

1. STEP 1. Resistance measurement at the ECALL & BCALL switch connector (terminal No. 2). 
   1. Disconnect the ECALL & BCALL switch connector, and measure at the wiring harness side.
   2. Check the resistance between the ECALL & BCALL switch connector (terminal No. 2) and body ground.

      OK: OK: The resistance should be 2 ohms or less 

      Q: Is the check result normal? 

      YES:  Go to Step  2.

      NO:  Repair the connector(s) or wiring harness.

2. STEP 2. Check the SOS switch/information switch indicator light. 

   Check that the SOS switch/information switch indicator light illuminates. Refer to ECALL & BCALL SWITCH  .

   Q: Is the check result normal? 

   YES:  Go to Step  3.

   NO:  Replace the ECALL & BCALL switch (Refer to ECALL & BCALL SWITCH  ).

3. STEP 3. Resistance measurement at between the TCU connector (IND1, IND4, IND5, IND6 terminals). 
   1. Disconnect the TCU and the ECALL & BCALL switch connector, and measure at the wiring harness side.
   2. Check the resistance between the TCU connector (IND1 terminal) and the ECALL & BCALL switch connector (terminal No. 4).

      OK: The resistance should be 2 ohms or less 

   3. Check the resistance between the TCU connector (IND4 terminal) and the ECALL & BCALL switch connector (terminal No. 5).

      OK: The resistance should be 2 ohms or less 

   4. Check the resistance between the TCU connector (IND5 terminal) and the ECALL & BCALL switch connector (terminal No. 15).

      OK: The resistance should be 2 ohms or less 

   5. Check the resistance between the TCU connector (IND6 terminal) and the ECALL & BCALL switch connector (terminal No. 16).

      OK: The resistance should be 2 ohms or less 

      Q: Is the check result normal? 

      YES:  Go to Step  4.

      NO:  Repair the connector(s) or wiring harness.

4. STEP 4. Using scan tool (M.U.T.-IIISE), check whether the DTC is set again. 

   Check again if the DTC is set in the TCU.

   CAUTION: To 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).
   1. Connect scan tool (M.U.T.-IIISE). Refer to "HOW TO CONNECT THE SCAN TOOL (M.U.T.-IIISE) ."
   2. Erase the DTC.
   3. Turn the ignition switch from OFF position to ON position.
   4. Check the DTC.

      Q: Is the DTC set? 

      YES:  Replace the TCU (Refer to TCU  ).

      NO:  The trouble can be an intermittent malfunction (Refer to How to use Troubleshooting/inspection Service Points - HOW TO COPE WITH INTERMITTENT MALFUNCTION ).