Mitsubishi Evolution X. Manual — part 943

HEADLIGHT

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CHASSIS ELECTRICAL

54A-133

Inspection Procedure 2: All the headlights (high-beam) do not illuminate.

CAUTION

Whenever the ECU is replaced, ensure that the power supply circuit, the ground circuit and the com-
munication circuit are normal.

.

TECHNICAL DESCRIPTION (COMMENT)

If both headlights (high-beam) do not illuminate nor-
mally, the headlight switch input circuit, headlight
relay (HIGH), or ETACS-ECU may have a problem.

.

TROUBLESHOOTING HINTS

• Malfunction of column switch

• Malfunction of headlight relay (HIGH)

• Malfunction of the ETACS-ECU

• Damaged harness wires and connectors

Headlight Relay (High-Beam) Circuit

ETACS-ECU

FUSIBLE
LINK

36

HEADLIGHT
RELAY (HIGH)

RELAY BOX
ENGINE
COMPARTMENT

AC709111

Connector: A-21X

AD

AC708972AP

Connector: C-312

ETACS-ECU

HEADLIGHT

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CHASSIS ELECTRICAL

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DIAGNOSIS

Required Special Tools:

• MB992006: Extra fine probe

• MB991223: Harness set

• MB991958: Scan Tool (M.U.T.-III Sub Assembly)

• MB991824: Vehicle Communication Interface (V.C.I.)

• MB991827: M.U.T.-III USB Cable

• MB991910: M.U.T.-III Main Harness A (Vehicles with

CAN communication system)

STEP 1. Using scan tool MB991958, read the diagnostic
trouble code.

CAUTION

To prevent damage to scan tool MB991958, always turn the
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting scan tool MB991958.
(1) Connect scan tool MB991958. Refer to "How to connect

scan tool (M.U.T.-III)

P.54A-105

."

(2) Turn the ignition switch to the "ON" position.
(3) Check whether the ETACS-ECU related DTC is set.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the DTC set?

YES : Diagnose the ETACS-ECU. Refer to ETACS,

Diagnosis

P.54A-582

.

NO : Go to Step 2.

AC608435

Data link connector

MB991827

MB991824

MB991910

AB

HEADLIGHT

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STEP 2. Using scan tool MB991958, check data list
Use the ETACS-ECU service data to check the signals related
to the operation of headlight function.

• Turn the headlight switch to the ON position.

• Turn the passing switch to the ON position.

Q: Do scan tool MB991958 display the items "Headlight

switch" and "Headlight switch (flasher)" as normal
condition?
YES : (Normal conditions are displayed for all items.) Go to

Step 3.

NO : (Normal condition is not displayed.) Troubleshoot the

ETACS-ECU. Refer to ETACS, Diagnosis

P.54A-639

.

STEP 3. Check headlight relay (HIGH) connector A-21X for
loose, corroded or damaged terminals, or terminals
pushed back in the connector.
Q: Is headlight relay (HIGH) connector A-21X in good

condition?
YES : Go to Step 4.
NO : Repair the damaged parts.

STEP 4. Check of headlight relay (HIGH)
Refer to

P.54A-189

.

Q: Is the headlight relay (HIGH) in good condition?

YES : Go to Step 5.
NO : Replace the headlight relay (HIGH). Verify that the

high-beam headlights illuminate normally.

Item No.

Item name

Normal
condition

Item 341

Headlight
switch

ON

Item No.

Item name

Normal
condition

Item 350

Headlight
switch (flasher)

ON

HEADLIGHT

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STEP 5. Check the battery power supply circuit to the
headlight relay (HIGH). Measure the voltage at headlight
relay (HIGH) connector A-21X

CAUTION

The top and bottom of the headlight relay (HIGH) are diffi-
cult to identify. Prior to inspection, confirm the triangle
mark on the relay box.
(1) Disconnect headlight relay (HIGH) connector A-21X and

measure the voltage available at the relay box side of the
connector.

(2) Measure the voltage between terminal 2 or 4 and ground.

OK: The voltage should measure approximately 12
volts (battery positive voltage).

Q: Is the measured voltage approximately 12 volts (battery

positive voltage)?
YES : Go to Step 6.
NO : Go to Step 8.

STEP 6. Check ETACS-ECU connector C-312 for loose,
corroded or damaged terminals, or terminals pushed back
in the connector.
Q: Is ETACS-ECU connector C-312 in good condition?

YES : Go to Step 7.
NO : Repair the damaged parts.

STEP 7. Check the wiring harness between headlight relay
(HIGH) connector A-21X (terminal 1) and ETACS-ECU
connector C-312 (terminal 13).

• Check the ground wires for open circuit.

Q: Is the wiring harness between headlight relay (HIGH)

connector A-21X (terminal 1) and ETACS-ECU
connector C-312 (terminal 13) in good condition?
YES : Go to Step 9.
NO : 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. Verify that
the high-beam headlights illuminate normally.