Mitsubishi Evolution X. Manual — part 942

HEADLIGHT

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CHASSIS ELECTRICAL

54A-129

.

TECHNICAL DESCRIPTION (COMMENT)

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

.

TROUBLESHOOTING HINTS

• Malfunction of column switch

• Malfunction of headlight relay (LOW)

• Malfunction of the ETACS-ECU

• Damaged harness wires and connectors

DIAGNOSIS

Required Special Tools:

• MB992006: Extra fine probe

• MB991223: Harness set

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

Headlight Relay (Low-Beam) Circuit <Discharge Type>

ETACS-ECU

FUSIBLE
LINK

36

HEADLIGHT
RELAY (LOW)

RELAY BOX
ENGINE
COMPARTMENT

AC709111

Connector: A-29X

AC

AC708972AP

Connector: C-312

ETACS-ECU

HEADLIGHT

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CHASSIS ELECTRICAL

54A-130

• 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.

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.

Q: Do scan tool MB991958 display the items "Headlight

switch" as normal condition?
YES : Go to Step 3.
NO : Troubleshoot the ETACS-ECU. Refer to ETACS,

Diagnosis

P.54A-639

.

AC608435

Data link connector

MB991827

MB991824

MB991910

AB

Item No.

Item name

Normal
condition

Item 341

Headlight
switch

ON

HEADLIGHT

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CHASSIS ELECTRICAL

54A-131

STEP 3. Check headlight relay (LOW) connector A-29X for
loose, corroded or damaged terminals, or terminals
pushed back in the connector.
Q: Is headlight relay (LOW) connector A-29X in good

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

STEP 4. Check the battery power supply circuit to the
headlight relay (LOW). Measure the voltage at headlight
relay (LOW) connector A-29X.

CAUTION

The top and bottom of the headlight relay (LOW) are diffi-
cult to identify. Prior to inspection, confirm the triangle
mark on the relay box.
(1) Disconnect headlight relay (LOW) connector A-29X 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 5.
NO : Go to Step 7.

STEP 5. 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 6.
NO : Repair the damaged parts.

STEP 6. Check the wiring harness between headlight relay
(LOW) connector A-29X (terminal 1) and ETACS-ECU
connector C-312 (terminal 6).

• Check the ground wires for open circuit.

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

connector A-29X (terminal 1) and ETACS-ECU
connector C-312 (terminal 6) in good condition?
YES (Vehicles without discharge headlight) : Go to Step

8.

YES (Vehicles with discharge headlight) : 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 low-beam headlights illuminate normally.

AC709325 AB

Harness side: A-29X

HEADLIGHT

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STEP 7. Check the wiring harness between headlight relay
(LOW) connector A-29X (terminal 2 or 4) and the fusible
link (36).

• Check the power supply line for open circuit.

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

connector A-29X (terminal 2 or 4) and fusible link (36) in
good condition?
YES (Vehicles without discharge headlight) : Go to Step

8.

YES (Vehicles with discharge headlight) : 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 low-beam headlights illuminate normally.

STEP 8. Temporarily replace the headlight relay (LOW),
and retest the system.
Temporarily replace the headlight relay (LOW), check that the
headlights (low-beam) illuminate normally.
Q: Does the headlights (low-beam) do not illuminate in

good condition?
YES : Replace the headlight relay (LOW).
NO : Replace the ETACS-ECU.

STEP 9. Check of headlight relay (LOW).
Refer to

P.54A-189

.

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

YES : Go to Step 10.
NO : Replace the headlight relay (LOW). Verify that the

low-beam headlights illuminate normally.

STEP 10. Retest the system
Q: Does the headlights (low-beam) do not illuminate in

good condition?
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

P.00-15

).

NO : Replace the ETACS-ECU.