Mitsubishi 380. Manual - part 342

AUTO-CRUISE CONTROL

ENGINE AND EMISSION CONTROL

17-36

DIAGNOSIS

Required Special Tools:

• MB991958: Diagnostic ToolDiagnostic Tool (MUT-III Sub 

Assembly)

• MB991824: V.C.I.

• MB991827: MUT-III USB Cable

• MB991910: MUT-III Main Harness A

• MB991223: Harness Set
• MB992044: ENGINE-ECU Check Harness

STEP 1. Using Diagnostic Tool MB991958, check data list 
item 74: Stoplamp Switch.

CAUTION

To prevent damage to Diagnostic Tool MB991958, always 
turn the ignition switch to the "LOCK" (OFF) position 
before connecting or disconnecting Diagnostic Tool 
MB991958. 
(1) Connect Diagnostic Tool MB991958 to the data link 

connector. (Refer to 

P.17-11

).

(2) Turn the ignition switch to the "ON" position.
(3) Set Diagnostic Tool MB991958 to data reading mode for 

auto-cruise control system. (Refer to 

P.17-11

).

• Item 74, Stoplamp Switch.

• When the brake pedal is depressed, the display on 

Diagnostic Tool MB991958 should be "ON".

• When the brake pedal is released, the display on 

Diagnostic Tool MB991958 should be "OFF".

(4) Turn the ignition switch to the "LOCK" (OFF) position.
(5) Disconnect Diagnostic Tool MB991958.

Q: Is the switch operating properly?

YES : Go to Step 14.
NO :  Go to Step 2.

STEP 2. Check the stoplamp operation.

Check the stoplamp operation.

• When the brake pedal is depressed, the stoplamp will 

illuminate.

• When the brake pedal is released, the stoplamp does 

not illuminate.

Q: Does the stoplamp illuminate (when the brake pedal is 

depressed) and the stoplamp does not illuminate (when 
the brake pedal is released)?
YES : Go to Step 3.
NO :  Go to Step 6.

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

AUTO-CRUISE CONTROL

ENGINE AND EMISSION CONTROL

17-37

STEP 3. Measure the terminal voltage at Engine ECU 
connector B-21.
(1) Disconnect all the connectors from the Engine ECU.
(2) Connect special tool MB992044 between the Engine ECU 

and the body-side harness connector.

(3) Turn the ignition switch to the "ON" position.

(4) Measure the terminal voltage between special tool 94-pin 

connector terminal 18 (Engine ECU connector B-21 
terminal 18) and ground.

• When the brake pedal is depressed, the voltage should 

measure battery positive voltage (approximately 12 
volts).

• When the brake pedal is released, the voltage should 

measure 1 volt or less.

(5) Turn the ignition switch to the "LOCK" (OFF) position.
(6) Disconnect special tool MB992044 between the Engine 

ECU and the body-side harness connector.

(7) Reconnect all the connectors to the Engine ECU.

Q: Is the measured voltage battery positive voltage 

(approximately 12 volts) when the brake pedal is 
depressed and 1 volt or less when the brake pedal is 
released?
YES : Go to Step 13.
NO :  Go to Step 4.

10DB133A

COVER

ENGINE

CONTROL

UNIT

AIR

CLEANER

16DB400A

COVER

ENGINE

CONTROL

UNIT

AIR

CLEANER

AUTO-CRUISE CONTROL

ENGINE AND EMISSION CONTROL

17-38

STEP 4. Check Engine ECU connector B-21 and stoplamp 
switch connector C-30 for loose, corroded or damaged 
terminals, or terminals pushed back in the connector.
Q: Are the connectors and terminals in good condition?

YES : Go to Step 5.
NO :  Repair or replace the damaged components. (Refer to 

GROUP 00E, Harness Connector Inspection 

P.00E-2

). Then go to Step 22.

10DB133A

COVER

ENGINE

CONTROL

UNIT

AIR

CLEANER

17DB045A

CONNECTOR: C-30

C-30

C-30 HARNESS
CONNECTOR:
COMPONENT SIDE

AUTO-CRUISE CONTROL

ENGINE AND EMISSION CONTROL

17-39

STEP 5. Check the harness wire between Engine ECU 
connector B-21 terminal 18 and stoplamp switch 
connector C-30 terminal 1 for damage.
Q: Is the harness wire in good condition?

YES : Go to Step 13.
NO :  Repair the damaged harness wire if possible, or as 

recommended, replace complete wiring harness. 
Then go to Step 22.

16DB400A

COVER

ENGINE

CONTROL

UNIT

AIR

CLEANER

17DB045A

CONNECTOR: C-30

C-30

C-30 HARNESS
CONNECTOR:
COMPONENT SIDE