Mitsubishi Grandis. Manual - part 69

SYMPTOM PROCEDURES

SMART WIRING SYSTEM (SWS) NOT USING SWS MONITOR

54B-273

Inspection Procedure M-2: The low-beam headlamps do not illuminate normally.

CAUTION

Whenever the ECU is replaced, ensure that the 
input and output signal circuits are normal.

COMMENTS ON TROUBLE SYMPTOM

If the low-beam headlamps do not illuminate, the 
headlamp switch input circuit or the front-ECU may 
be defective.

POSSIBLE CAUSES

• Malfunction of the column switch

• Malfunction of the front-ECU

• Damaged harness wires and connectors

DIAGNOSTIC PROCEDURE

Step 1. Pulse check
Check the input signal from the headlamp switch.

OK: The MUT-III sounds or the voltmeter 
needle fluctuates.

Q: Are the check result normal?

Wire colour code
B : Black     LG : Light green     G : Green     L : Blue
W : White     Y : Yellow     SB : Sky blue     BR : Brown
O : Orange     GR : Gray     R : Red     P : Pink     V : Violet

FRONT-ECU

HEADLAMP
RELAY: LO

RELAY
BOX

INPUT SIGNAL

· HEADLAMP AUTOMATIC
  SHUTDOWN
· HEADLAMP SWITCH

HEADLAMP (LO: LH)

HEADLAMP (LO: RH)

Headlamp Relay (Low-Beam) Circuit

FUSIBLE LINK 

26

System switch

Check condition

Ignition switch (IG1)

When turned from ACC 
to ON

Headlamp switch

When the lighting switch 
is turned to the 
HEADLAMP position

SYMPTOM PROCEDURES

SMART WIRING SYSTEM (SWS) NOT USING SWS MONITOR

54B-274

All the signals are received normally. : 

Go to Step 

2.

The ignition switch (IG1) signal is not received. : 

Refer to inspection procedure Q-2 "The 
ignition switch (IG1) signal is not received 

P.54B-420

."

The headlamp switch signal is not received. : 

Refer to inspection procedure Q-6 "The 
column switch (lighting and turn-signal lamp 
and headlamp washer switch) signal is not 
received 

P.54B-438

."

Step 2. Connector check: A-14X front-ECU 
connector

Q: Is the check result normal?

YES : 

Go to Step 3.

NO : 

Repair the defective connector.

Step 3. Voltage measurement at A-14X front-ECU 
connector.

(1) Remove the front-ECU, and measure at the relay 

box side.

(2) Voltage between A-14X front-ECU connector 

terminal Nos.3 and 4 body earth

OK: System voltage

Q: Is the check result normal?

YES : 

Go to Step 5.

NO : 

Go to Step 4.

Step 4. Check the wiring harness between A-14X 
front-ECU connector terminal Nos.3 and 4 the 
fusible link (26).

• Check the power supply line for open circuit.

Q: Is the check result normal?

YES : 

The trouble can be an intermittent 

malfunction (Refer to GROUP 00 

− How to 

Cope with Intermittent Malfunction 

P.00-5

).

NO : 

Repair the wiring harness.

Step 5. Retest the system.
Check that the low-beam headlamps illuminate 
normally.

Q: Is the check result normal?

YES : 

The trouble can be an intermittent 

malfunction (Refer to GROUP 00 

− How to 

Cope with Intermittent Malfunction 

P.00-5

).

NO : 

Replace the front-ECU.

AC311521AB

Connector: A-14X

Relay box side

AC311521AB

Connector: A-14X

Relay box side

AC310507CD

Connector A-14X
(Relay box side)

AC311521AB

Connector: A-14X

Relay box side

SYMPTOM PROCEDURES

SMART WIRING SYSTEM (SWS) NOT USING SWS MONITOR

54B-275

Inspection Procedure M-3: The high-beam headlamps do not illuminate normally.

CAUTION

Whenever the ECU is replaced, ensure that the 
input and output signal circuits are normal.

COMMENTS ON TROUBLE SYMPTOM

If the high-beam headlamps do not illuminate, the 
dimmer switch input circuit or the front-ECU may be 
defective.

POSSIBLE CAUSES

• Malfunction of the column switch

• Malfunction of the front-ECU

• Damaged harness wires and connectors

DIAGNOSTIC PROCEDURE

Step 1. Check that the headlamps operate.
Check that the low-beam headlamps illuminate and 
extinguish normally.

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

Refer to inspection procedure M-2 "The 
low-beam headlamps do not illuminate 
normally 

P.54B-273

."

Step 2. Pulse check
Check the input signal from the dimmer switch.

OK: The MUT-III sounds or the voltmeter 
needle fluctuates.

Q: Is the check result normal?

YES : 

Go to Step 3.

NO : 

Refer to inspection procedure Q-6 "The 
column switch (lighting and turn-signal lamp 
and headlamp washer switch) signal is not 
received 

P.54B-438

."

Step 3. Retest the system.
Check that the high-beam headlamps illuminate 
normally.

Q: Is the check result normal?

YES : 

The trouble can be an intermittent 

malfunction (Refer to GROUP 00 

− How to 

Cope with Intermittent Malfunction 

P.00-5

).

NO : 

Replace the front-ECU.

FUSIBLE LINK 

26

Wire colour code
B : Black     LG : Light green     G : Green     L : Blue
W : White     Y : Yellow     SB : Sky blue     BR : Brown
O : Orange     GR : Gray     R : Red     P : Pink     V : Violet

FRONT-ECU

HEADLAMP
RELAY: HI

RELAY
BOX

INPUT SIGNAL

· HEADLAMP AUTOMATIC
  SHUTDOWN
· HEADLAMP SWITCH

HEADLAMP (HI: LH)

HEADLAMP (HI: RH)

Headlamp Relay (High-Beam) Circuit

System switch

Check condition

Dimmer switch

When the dimmer switch 
is turned from off to on

SYMPTOM PROCEDURES

SMART WIRING SYSTEM (SWS) NOT USING SWS MONITOR

54B-276

Inspection Procedure M-4: The high-beam and low-beam headlamps do not illuminate when the 
passing switch is operated.

CAUTION

Whenever the ECU is replaced, ensure that the 
input and output signal circuits are normal.

COMMENTS ON TROUBLE SYMPTOM

If the low-beam and high-beam headlamps are 
normal, the passing switch input signal circuit or the 
front-ECU may be defective.

POSSIBLE CAUSES

• Malfunction of the column switch

• Malfunction of the front-ECU

• Damaged harness wires and connectors

DIAGNOSTIC PROCEDURE

Step 1. Check that the headlamps operate.
Check that the low-beam and high-beam headlamps 
work normally.

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

Repair the headlamps. Refer to trouble 
symptom chart 

P.54B-74

.

Step 2. Pulse check
Check the input signal from the passing switch.

OK: The MUT-III sounds or the voltmeter 
needle fluctuates.

Q: Is the check result normal?

YES : 

Go to Step 3.

NO : 

Refer to inspection procedure Q-6 "The 
column switch (lighting and turn-signal lamp 
and headlamp washer switch) signal is not 
received 

P.54B-438

."

Step 3. Retest the system.
When the passing switch is turned on, check if the 
headlamps illuminate normally.

Q: Is the check result normal?

YES : 

The trouble can be an intermittent 

malfunction (Refer to GROUP 00 

− How to 

Cope with Intermittent Malfunction 

P.00-5

).

NO : 

Replace the front-ECU.

Inspection Procedure M-5: The headlamp automatic-shutdown function does not work normally.

CAUTION

Whenever the ECU is replaced, ensure that the 
input and output signal circuits are normal.

System switch

Check condition

Passing lamp switch

When the passing switch 
is turned from off to on

ETACS-ECU

INPUT SIGNAL

· DRIVER'S DOOR SWITCH

· TAIL LAMP SWITCH

· IGNITION SWITCH (IG1)

· HEADLAMP SWITCH

Headlamp Automatic Shutdown Function