DTC B1864: Relay Box Connection: Diagnosis

Required Special Tools 

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

1. STEP 1. Resistance measurement at the ECALL relay box assembly connector (GND terminal). 
   1. Disconnect the ECALL relay box assembly connector, and measure at the wiring harness side.
   2. Check the resistance between the ECALL relay box assembly connector (GND terminal) and body ground.

      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. Voltage measurement at the ECALL relay box assembly connector (RLE1, RLE2 terminal). 
   1. Disconnect the ECALL relay box assembly connector, and measure at the wiring harness side.
      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).
   2. Connect scan tool (M.U.T.-IIISE). Refer to "HOW TO CONNECT THE SCAN TOOL (M.U.T.-IIISE) ."
   3. Turn the ignition switch from OFF position to ON position.
      CAUTION: Execute item No. 4 "Door speaker check (Beep)" in the scan tool (M.U.T.-IIISE) special function "Test", and measure the voltage.
   4. Check the voltage between the ECALL relay box assembly connector (RLE1 terminal) and body ground.

      OK: Approximately 5 volts 

   5. Turn the ignition switch from OFF position to ON position.
      CAUTION: Execute item No. 4 "Door speaker check (Beep)" in the scan tool (M.U.T.-IIISE) special function "Test", and measure the voltage.
   6. Check the voltage between the ECALL relay box assembly connector (RLE2 terminal) and body ground.

      OK: Approximately 5 volts 

      Q: Is the check result normal? 

      YES:  Replace the ECALL relay box assembly (Refer to ECALL RELAY BOX ASSEMBLY  ).

      NO:  Go to Step  3.

3. STEP 3. Resistance measurement at the TCU connector (RL01, RL02 terminals). 
   1. Disconnect the TCU and the ECALL relay box assembly connector, and measure at the wiring harness side.
   2. Check the resistance between the TCU connector (RL01 terminal) and the ECALL relay box assembly connector (RLE1 terminal).

      OK: The resistance should be 2 ohms or less 

   3. Check the resistance between the TCU connector (RL02 terminal) and the ECALL relay box assembly connector (RLE2 terminal).

      OK: The resistance should be 2 ohms or less 

   4. Check the resistance between the TCU connector (RL01 terminal) and body ground.

      OK: No continuity 

   5. Check the resistance between the TCU connector (RL02 terminal) and body ground.

      OK: No continuity 

   6. Check the resistance between the TCU connector (RL01 terminal) and the ECALL relay box assembly connector (except RLE1 terminal).

      OK: No continuity 

   7. Check the resistance between the TCU connector (RL02 terminal) and the ECALL relay box assembly connector (except RLE2 terminal).

      OK: No continuity 

      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.

   1. Erase the DTC.
   2. Turn the ignition switch from OFF position to ON position.
   3. 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 ).