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Inspection Procedure 4: Even when the steering wheel voice control switch is operated, the conversation is not possible.


caution Before replacing the ECU, ensure that the power supply circuit, the ground circuit and the communication circuit are normal.






FUNCTION


When the steering wheel voice control switch is operated, the switch signal is transmitted to the radio and CD player <vehicles without MMCS> or audio visual navigation unit <vehicles with MMCS>. Then, via the CAN communication, the signal is transmitted from the radio and CD player <vehicles without MMCS> or audio visual navigation unit <vehicles with MMCS> to the hands free module.

TROUBLE JUDGMENT CONDITIONS


If the conversation is not possible even when the steering wheel voice control switch is operated, the steering wheel voice control switch or radio and CD player <vehicles without MMCS> or the audio visual navigation unit <vehicles with MMCS> may be defective.

TROUBLESHOOTING HINTS



DIAGNOSIS
Required Special Tools:
  • MB991223: Harness Set
  • MB992006: Extra Fine Probe

STEP 1. Check the steering wheel audio remote control switch.
Check that the radio and CD player <vehicles without MMCS> or audio visual navigation unit <vehicles with MMCS> can be operated normally using the steering wheel audio remote control switch.

Q. Is it possible to normally operate the radio and CD player <vehicles without MMCS> or audio visual navigation unit <vehicles with MMCS> using the steering wheel audio remote control switch?
Go to Step 2.
Diagnose the steering wheel audio remote control switch (Refer to <vehicles without MMCS> or <vehicles with MMCS>.)

STEP 2. Using scan tool MB991958, diagnose the CAN bus line.

(1)
caution To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
Connect scan tool MB991958 to the data link connector.
(2)Turn the ignition switch to the "ON" position.
(3)Diagnose the CAN bus line.
(4)Turn the ignition switch to "LOCK" (OFF) position.

Q. Is the CAN bus line found to be normal?

Go to Step 3.

Repair the CAN bus line (Refer to GROUP 54C, Diagnosis ).

STEP 3. Check the steering wheel voice-control switch.


Remove the steering wheel voice control switch. Then check continuity between the switch terminals.
Switch Position
 Tester Connection
 Measurement Value
No push
 2 - 3
 Approximately 74 kΩ
"Speech" switch
 Approximately 1.5 kΩ
"Pick-up" switch
 Approximately 3.3 kΩ
"Hang-up" switch
 Approximately 5.0 kΩ

Q. Is the steering wheel voice control switch in good condition?

Go to Step 4.

Replace the steering wheel voice control switch.

STEP 4. Check the steering wheel audio remote control switch.

Remove the steering wheel audio remote control switch. Then check continuity between the switch terminals.
Switch Position
 Tester Connection
 Measurement Value
No push
 2 - 3
 Approximately 3.1 kΩ

Q. Is the steering wheel audio remote control switch in good condition?

Go to Step 5.

Replace the steering wheel audio remote control switch.

STEP 5. Check steering wheel voice control switch connector C-209 and steering wheel audio remote control switch connector C-202 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q. Are steering wheel voice control switch connector C-209 and steering wheel audio remote control switch connector C-202 in good condition?
Go to Step 6.
Repair or replace the damaged component(s). Refer to GROUP 00E, Harness Connector Inspection . The steering remote control switch should work normally.

STEP 6. Check the wiring harness between steering wheel voice-control switch connector C-209 (terminal 3) and steering wheel audio remote control switch connector C-202 (terminal 3).

  • Check the communication line for open circuit and short circuit.

Q. Is the wiring harness between steering wheel voice-control switch connector C-209 (terminal 3) and steering wheel audio remote control switch connector C-202 (terminal 3) in good condition?
Go to Step 7.
The wiring harness may be damaged or the connector(s) may have loose, corroded or damaged terminals, or terminals pushed back in the connector. Repair the wiring harness as necessary.

STEP 7. Check the wiring harness between steering wheel voice-control switch connector C-209 (terminal 2) and clock spring connector C-204 (terminal 4).

  • Check the communication line for open circuit and short circuit.

Q. Is the wiring harness between steering wheel voice-control switch connector C-209 (terminal 2) and clock spring connector C-204 (terminal 4) in good condition?

    Go to Step 8.
The wiring harness may be damaged or the connector(s) may have loose, corroded or damaged terminals, or terminals pushed back in the connector. Repair the wiring harness as necessary.

STEP 8. Retest the system
Check that the hands free cellular phone system works normally when the steering wheel voice control switch is operated.

Q. Check that the hands free cellular phone system works normally when the steering wheel voice control switch is operated.
The trouble can be an intermittent malfunction (Refer to GROUP 00, How to use Troubleshooting/inspection Service Points, How to Cope with Intermittent Malfunction ).
Replace the radio and CD player <vehicles without MMCS> or audio visual navigation unit <vehicles with MMCS>.