DTC B1866: Connection abnormality, +B: Diagnosis

Required Special Tools 

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

1. STEP 1. Voltage measurement at the TCU connector (+B terminal). 
   1. Disconnect the TCU connector, and measure at the wiring harness side.
   2. Check the voltage between the TCU connector (+B terminal) and body ground.

      OK: The voltage should measure approximately 12 volts (battery positive voltage). 

      Q: Is the check result normal? 

      YES:  Go to Step  2.

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

2. STEP 2. 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 "LOCK" (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 ).