Code No.B1857: Microphone Connection


caution When replacing the ECU, always check that the communication circuit is normal.

DIAGNOSTIC FUNCTION


When the system detects that the microphone is disconnected for 5 seconds or more, the e-Call control unit sets diagnosis code No. B1857.
note When diagnosis code No. B1857 is set, the e-Call switch flashes in green.

PROBABLE CAUSES



DIAGNOSIS PROCEDURE


STEP 1. Voltage measurement at the microphone connector (MACC terminal).


(1)Disconnect the microphone connector, and measure at the wiring harness side.
(2)Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
(3)Check the voltage between the microphone connector terminal MACC and body earth.
OK: Approximately 5 V

Q. Is the check result normal?

Go to Step 3

Go to Step 2

STEP 2. Resistance measurement at between the e-Call control unit and the microphone connector (SNSI or MACC terminals).


(1)Disconnect the e-Call control unit and microphone connector, and measure at the wiring harness side.
(2)Check the resistance between the e-Call control unit connector terminal SNSI and microphone connector terminal MACC.
OK: Continuity exists (2 Ω or less)

Q. Is the check result normal?

Replace the e-Call control unit (Refer to ).

Repair the connector(s) or wiring harness.

STEP 3. Resistance measurement at the microphone connector (S99 terminal).


(1)Disconnect the microphone connector, and measure at the wiring harness side.
(2)Check the resistance between the microphone terminal S99 and body earth.
OK: Continuity exists (2 Ω or less)

Q. Is the check result normal?

Replace the microphone (Refer to ).

Go to Step 4

STEP 4. Resistance measurement at the e-Call control unit connector (MI- terminal).


(1)Disconnect the e-Call control unit and microphone connector, and measure at the wiring harness side.
(2)Check the resistance between the e-Call control unit connector terminal MI- microphone connector terminal S99.
OK: Continuity exists (2 Ω or less)

Q. Is the check result normal?

YES <Vehicles without smartphone link display audio and hands free-ECU> : Go to Step 7

YES <Vehicles with smartphone link display audio or hands free-ECU> : Go to Step 5

Repair the connector(s) or wiring harness.

STEP 5. Resistance measurement at the e-Call control unit connector (MO- terminal).


(1)Disconnect the e-Call control unit, and measure at the wiring harness side.
(2)Check the resistance between the e-Call control unit connector terminal MO- and body earth.
OK: Continuity exists (2 Ω or less)

Q. Is the check result normal?

Go to Step 7

Go to Step 6

STEP 6. Resistance measurement at between the e-Call control unit connector (MO- terminal) and the smartphone link display audio connector (MIC- terminal) or hands free-ECU connector (MIC- terminal).


(1)Disconnect the e-Call control unit and smartphone link display audio or hands free-ECU, and measure at the wiring harness side.
(2)Check the resistance between the e-Call control unit connector terminal MO- and smartphone link display audio connector terminal MIC- or hands free-ECU connector terminal MIC-.
OK: Continuity exists (2 Ω or less)

Q. Is the check result normal?

Replace the multivision display (Refer to ) or Replace the hands free-ECU (Refer to ).

Repair the connector(s) or wiring harness.

STEP 7. Check whether the diagnosis code is set again.


Check again if the diagnosis code is set in the e-Call control unit.
(1)Erase the diagnosis code.
(2)Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
(3)Execute "Test" on the M.U.T.-III special function.

  • Item No.5: Microphone check (Door speaker)
(4)Check if diagnosis code is set.

Q. Is the diagnosis code set?

Replace the e-Call control unit (Refer to ).

Intermittent malfunction is suspected (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction).