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DTC B1857: Microphone Connection
 
 
cautionWhen replacing the ECU, always check that the communication circuit is normal.
 
 
TROUBLE JUDGMENT
Check Conditions
  • Ignition switch: ON
Judgment Criterion
  • When the system detects that the microphone unit is disconnected for 5 seconds or more.
 
 
TROUBLESHOOTING HINTS
  • The wiring harness or connectors may have loose, corroded, or damaged terminals, or terminals pushed back in the connector
  • The microphone unit may be defective
  • The multivision display may be defective
  • The TCU may be defective
 
 
DIAGNOSIS
Required Special Tools
  • MB991223: Wiring harness set
  • MB992006: Extra fine probe
STEP 1. Voltage measurement at the microphone unit connector (terminal No.1).
(1) Disconnect the microphone unit connector, and measure at the wiring harness side.
(2) Turn the ignition switch from OFF position to ON position.
(3) Check the voltage between the microphone unit connector (terminal No.1) and body ground.
OK: Approximately 5 volts
Is the check result normal?
Go to Step 3.
Go to Step 2.
 
STEP 2. Resistance measurement at the TCU connector (SNSI terminal).
(1) Disconnect the TCU and the microphone unit connector, and measure at the wiring harness side.
(2) Check the resistance SNSI line between the TCU connector and the microphone unit connector.
OK: The resistance should be 2 ohms or less
Is the check result normal?
Go to Step 7.
Repair the connector(s) or wiring harness.
 
STEP 3. Resistance measurement at the microphone unit connector (terminal No. 3).
(1) Disconnect the microphone unit connector, and measure at the wiring harness side.
(2) Check the resistance between the microphone unit connector (terminal No. 3) and body ground.
OK: The resistance should be 2 ohms or less
Is the check result normal?
Replace the microphone unit.
Go to Step 4.
 
STEP 4. Resistance measurement at the TCU connector (MI- terminal).
(1) Disconnect the TCU and the microphone unit connector, and measure at the wiring harness side.
(2) Check the resistance between the TCU connector (MI- terminal) and microphone unit connector (terminal No. 1).
OK: The resistance should be 2 ohms or less
Is the check result normal?
: Go to Step 5.
Repair the connector(s) or wiring harness.
 
STEP 5. Resistance measurement at the TCU connector (MO- terminal).
(1) Disconnect the TCU, and measure at the wiring harness side.
(2) Check the resistance between the TCU connector (MO- terminal) and body ground.
OK: The resistance should be 2 ohms or less
Is the check result normal?
Go to Step 7.
Go to Step 6.
 
STEP 6. Resistance measurement at the TCU connector (MO- terminal).
(1) Disconnect the TCU connector and the multivision display connector, and measure at the wiring harness side.
(2) Check the resistance between the TCU connector (MO- terminal) and the multivision display connector (MIC+ terminal).
OK: The resistance should be 2 ohms or less
Is the check result normal?
Replace the multivision display.
Repair the connector(s) or wiring harness.
 
STEP 7. 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)
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 (M.U.T.-IIISE) ."
(2) Erase the DTC.
(3) Turn the ignition switch from OFF position to ON position.
(4) Execute "Test" on the scan tool (M.U.T.-IIISE) special function.
  • Item No.5: Microphone check (Door speaker)
(5) Check the DTC.
Is the DTC set?
Replace the TCU (Refer to ).
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction ).