Lancer LS L4-2.0L SOHC (2002)
Headlight Relay (Low-beam) Circuit
NOTE: This troubleshooting requires use of scan tool MB991502 and SWS monitor kit MB991862. For details of how to use the SWS monitor, refer
to "How to use SWS monitor".
CIRCUIT OPERATION
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When the lighting switch is set to "HEAD" position, the "HEAD" signal is sent through the column-ECU (incorporated in the column switch) to
the front-ECU. IF the front-ECU receives the "HEAD" signal through the column-ECU, the front-ECU turns on the headlight relay (incorporated
in the front-ECU), thus causing the headlights to illuminate. The headlights always illuminate at low-beam by the headlight dimmer switch
automatic resetting function.
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If the SWS communication line is defective, the front-ECU operates the headlights by using the other communication lines (headlight backup
circuit) instead of that line.
TECHNICAL DESCRIPTION (COMMENT)
If the headlights (low-beam) do not illuminate normally, the column switch or the front-ECU may be defective.
TROUBLESHOOTING HINTS
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Malfunction of column switch (turn-signal light and lighting switch)
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Malfunction of the front-ECU
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Damaged harness wires or connectors
DIAGNOSIS
Required Special Tools:
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MB991223: Test Harness Set
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MB991502: Scan Tool (MUT-II)
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MB991862: SWS monitor kit