Mitsubishi Lancer (4A9 engine). Manual - part 199

HANDS FREE ECU

CHASSIS ELECTRICAL

54A-458

CIRCUIT OPERATION

• The ACC signal is received C-41 hands free ECU 

connector terminal No.15 from C-105 radio and 
CD player connector terminal No.17.

• From the fusible link to C-128 intermediate con-

nector, the hands free ECU uses the same power 
supply circuit as that of AUDIO display (centre 
panel unit) as well as that of radio and CD player. 
Therefore, check first if the AUDIO display (cen-
tre panel unit) is displayed. If the AUDIO display 
(centre panel unit) is not displayed, carry out in 
advance the troubleshooting of "The radio and 
CD player does not operate normally by operat-
ing the audio control unit of the centre panel unit". 
(Refer to  <Vehicles without Auto Stop & Go 
(AS&G) System> or  <Vehicles with Auto Stop & 
Go (AS&G) System>.)

PROBABLE CAUSES

• Damaged harness wires and connectors

• The DC/DC converter may be defective.<Vehi-

cles with Auto Stop & Go (AS&G) System>

• Malfunction of the hands free ECU

• Malfunction of the radio and CD player

• Damaged harness wires and connectors

DIAGNOSIS PROCEDURE

STEP 1. Check the radio and CD player 
operation.
Check if the radio and CD player work normally and 
the sound is output.

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

Troubleshoot the radio and CD player 
(Refer to ).

STEP 2. Connector check: C-41 hands free ECU 
connector

Q: Is the check result normal?

YES : 

Go to Step 3.

NO : 

Repair the defective connector.

STEP 3. Resistance measurement at C-41 hands 
free ECU connector.
(1) Disconnect the connector, and measure at the 

wiring harness side.

(2) Check the continuity between terminal 17 and 

earth.

OK: Continuity exists (2 

Ω or less)

Q: Is the check result normal?

YES : 

Go to Step 5.

NO : 

Go to Step 4.

STEP 4. Check the wiring harness between C-41 
hands free ECU connector terminal No.17 and 
body earth.

• Check the body earth wires for open circuit.

Q: Is the check result normal?

YES : 

The trouble can be an intermittent 

malfunction (Refer to GROUP 00 

− How to 

use Troubleshooting/inspection Service 
Points 

− How to Cope with Intermittent 

Malfunction ).

NO : 

Repair the wiring harness.

STEP 5. Voltage measurement at C-41 hands free 
ECU connector.
(1) Disconnect C-41 hands free ECU connector, and 

measure at the wiring harness side.

(2) Measure the voltage between terminal No.1 and 

body earth.

OK: System voltage

Q: Is the check result normal?

YES : 

Go to Step 8.

NO : 

Go to Step 6.

ACB02648

AI

Connector: C-41 <RHD>

ACB02647

Connector: C-105 <RHD>

AP

C-105

HANDS FREE ECU

CHASSIS ELECTRICAL

54A-459

STEP 6. Connector check: C-128 intermediate 
connector

Q: Is the check result normal?

YES : 

Go to Step 7.

NO : 

Repair the defective connector.

STEP 7. Check the wiring harness between C-41 
hands free connector terminal No.1 and C-128 
intermediate connector terminal No.9.

• Check the power supply line for open circuit and 

short circuit.

Q: Is the check result normal?

YES : 

The trouble can be an intermittent 

malfunction (Refer to GROUP 00, How to 
use Troubleshooting/inspection Service 
Points, How to Cope with Intermittent 
Malfunction ).

NO : 

Repair the wiring harness.

STEP 8. Voltage measurement at C-41 hands free 
ECU connector.
(1) Disconnect C-41 hands free ECU connector, and 

measure at the wiring harness side.

(2) Turn the ignition switch to "ACC" position.
(3) Measure the voltage between terminal No.15 and 

body earth.

OK: 1V or less

Q: Is the check result normal?

YES : 

Replace the hands free ECU.

NO : 

Go to Step 9.

STEP 9. Connector check: C-105 radio and CD 
player connector

Q: Is the check result normal?

YES : 

Go to Step 10.

NO : 

Repair the defective connector.

STEP 10. Check the harness wire between C-105 
radio and CD player connector terminal No.17 
and C-41 hands free ECU connector terminal 
No.15.

• Check the signal line for open circuit and short 

circuit.

Q: Is the check result normal?

YES : 

Replace the radio and CD player.

NO : 

Repair the wiring harness.

Inspection Procedure 1: Check the hands free ECU power supply circuit. <Vehicles with MMCS>

CAUTION

Before replacing the ECU, ensure that the power 
supply circuit, the earth circuit and the communi-
cation circuit are normal.

CIRCUIT OPERATION

• The ACC signal is received C-41 hands free ECU 

connector terminal No.15 from C-141 multivision 
display connector terminal No.82.

• From the fusible link to C-128 intermediate con-

nector, the hands free ECU uses the same power 
supply circuit as that of multivision display. There-
fore, check first if the multivision display operates 
normally. If the multivision display does not oper-
ate normally, carry out in advance the trouble-
shooting of "No navigation screen is displayed". 
(Refer to  <Vehicles without Auto Stop & Go 
(AS&G) System> or  <Vehicles with Auto Stop & 
Go (AS&G) System>.)

ACB02646

AI

C-141

C-66

Connectors: C-41, C-141 <LHD>

ACB02648

AJ

Connectors: C-41, C-141 <RHD>

C-141

C-41

HANDS FREE ECU

CHASSIS ELECTRICAL

54A-460

PROBABLE CAUSES

• The DC/DC converter may be defective.<Vehi-

cles with Auto Stop & Go (AS&G) System>

• Damaged harness wires and connectors

• Malfunction of the hands free ECU

• Malfunction of the multivision display

• Damaged harness wires and connectors

DIAGNOSIS PROCEDURE

STEP 1. Check the multivision display operation.
Check if the multivision display work normally and 
the sound is output.

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

Troubleshoot the multivision display (Refer 
to ).

STEP 2. Connector check: C-41 hands free ECU 
connector

Q: Is the check result normal?

YES : 

Go to Step 3.

NO : 

Repair the defective connector.

STEP 3. Resistance measurement at C-41 hands 
free ECU connector.
(1) Disconnect the connector, and measure at the 

wiring harness side.

(2) Check the continuity between terminal 17 and 

earth.

OK: Continuity exists (2 

Ω or less)

Q: Is the check result normal?

YES : 

Go to Step 5.

NO : 

Go to Step 4.

STEP 4. Check the wiring harness between C-41 
hands free ECU connector terminal No.17 and 
body earth.

• Check the body earth wires for open circuit.

Q: Is the check result normal?

YES : 

The trouble can be an intermittent 

malfunction (Refer to GROUP 00 

− How to 

use Troubleshooting/inspection Service 
Points 

− How to Cope with Intermittent 

Malfunction ).

NO : 

Repair the wiring harness.

STEP 5. Voltage measurement at C-41 hands free 
ECU connector.
(1) Disconnect C-41 hands free ECU connector, and 

measure at the wiring harness side.

(2) Measure the voltage between terminal No.1 and 

body earth.

OK: System voltage

Q: Is the check result normal?

YES : 

Go to Step 8.

NO : 

Go to Step 6.

STEP 6. Connector check: C-128 intermediate 
connector

Q: Is the check result normal?

YES : 

Go to Step 7.

NO : 

Repair the defective connector.

STEP 7. Check the wiring harness between C-41 
hands free connector terminal No.1 and C-128 
intermediate connector terminal No.9.

• Check the power supply line for open circuit and 

short circuit.

Q: Is the check result normal?

YES : 

The trouble can be an intermittent 

malfunction (Refer to GROUP 00, How to 
use Troubleshooting/inspection Service 
Points, How to Cope with Intermittent 
Malfunction ).

NO : 

Repair the wiring harness.

STEP 8. Voltage measurement at C-41 hands free 
ECU connector.
(1) Disconnect C-41 hands free ECU connector, and 

measure at the wiring harness side.

(2) Turn the ignition switch to "ACC" position.
(3) Measure the voltage between terminal No.15 and 

body earth.

OK: 1V or less

Q: Is the check result normal?

YES : 

Replace the hands free ECU.

NO : 

Go to Step 9.

STEP 9. Connector check: C-141 multivision 
display connector

Q: Is the check result normal?

YES : 

Go to Step 10.

NO : 

Repair the defective connector.

HANDS FREE ECU

CHASSIS ELECTRICAL

54A-461

STEP 10. Check the harness wire between C-141 
multivision display connector terminal No.82 and 
C-41 hands free ECU connector terminal No.15.

• Check the signal line for open circuit and short 

circuit.

NOTE: Prior to the wiring harness inspection, check 
the intermediate connector C-140, and repair if nec-
essary.

Q: Is the check result normal?

YES : 

Replace the radio and CD player.

NO : 

Repair the wiring harness.

Inspection Procedure 2: The USB adapter data cannot be replayed. <Vehicles with radio and CD 
player>

CAUTION

Before replacing the hands free ECU, ensure that the power supply circuit, the earth circuit and the 
communication circuit are normal.

COMMENTS ON TROUBLE SYMPTOM
If the sound replay is impossible with the USB mode, 
the USB adapter, USB cable, hands free ECU, or 
radio and CD player may be defective, or a commu-
nication error between the radio and CD player and 
hands free ECU may have occurred.
NOTE: Before troubleshooting, check that the music 
file (the customer tried to replay) can be replayed. 

PROBABLE CAUSES

• The radio and CD player may be defective.

• The hands free ECU may be defective.

• The USB adapter may be defective.

• The USB cable may be defective.

• Damaged harness wires and connectors

DIAGNOSIS PROCEDURE

STEP 1. Check the radio and CD player 
operation.
Check if the radio and CD player normally and the 
sound is output.

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

Troubleshoot the radio and CD player. 
(Refer to .)

STEP 2. Check the diagnosis mode
Check if the hands free-ECU can be switched to the 
diagnosis mode.(Refer to .)

Q: Is the check result normal?

YES : 

Go to Step 3.

NO : 

Perform Inspection Procedure 5 
"DIAGNOSIS MODE cannot be made an 
entry."(Refer to .)

ACA00892

Connectors: C-41, C-105 <LHD>

AL

C-105

C-41

ACA00896

AD

Connector: C-41 <RHD>

ACA00895AM

Connector: C-105 <RHD>

C-105