Page 6 of 94

ENGINE COMPARTMENT CONNECTION UNIT
Fault finding - Introduction87G
87G - 6V7 MR-372-J84-87G050$055.mif
UPC
Vdiag No.: 48, 4C
4. FAULT FINDING PROCEDURE (continued)
Wiring check
Fault finding problems
Disconnecting the connectors and/or manipulating the wiring harness may temporarily remove the cause of a fault.
Electrical measurements of voltage, resistance and insulation are generally correct, especially if the fault is not
present when the analysis is made (stored fault).
Visual inspection
Look for damage under the bonnet and in the passenger compartment.
Carefully check the fuses, insulators and wiring harness routing.
Look for signs of oxidation.
Tactile inspection
While manipulating the wiring harness, use the diagnostic tool to note any change in fault status from stored to
present.
Make sure that the connectors are properly locked.
Apply light pressure to the connectors.
Twist the wiring harness.
If there is a change in status, try to locate the source of the fault.
Inspection of each component
Disconnect the connectors and check the appearance of the clips and tabs, as well as the crimping (no crimping on
the insulating section).
Make sure that the clips and tabs are properly locked in the sockets.
Check that no clips or tabs have been dislodged during connection.
Check the clip contact pressure using an appropriate model of tab.
Continuity, insulation and resistance check
Check the continuity of entire lines, then section by section.
Look for a short circuit to earth, to + 12 V or to another wire.
If a fault is detected, repair or replace the wiring harness.
Page 24 of 94

ENGINE COMPARTMENT CONNECTION UNIT
Fault finding - Interpretation of faults87G
87G-24V7 MR-372-J84-87G050$330.mif
UPC
Vdiag No.: 48, 4C
DF012
PRESENT
OR
STOREDALTERNATOR
1.DEF: Alternator mechanical or electrical fault
NOTESConditions for applying the fault finding procedure to present faults:
The fault is declared present after the engine has been running for at least 1 minute.
Special note:
The fault illuminates the Battery and STOP warning lights on the instrument panel.
Use Wiring Diagrams Technical Note for Mégane II or Scénic II.
1.DEF
NOTESNone.
Check the fitting, condition and tension of the accessories drive belt.
Visually check that the alternator is not clogged.
Clean out the alternator cooling vents using an air gun.
Check the wiring, the connections and the earths (see Test no. 1 Wiring test).
If the connection is faulty and if there is a repair procedure (see Technical Note 6015A, Electrical wiring repair,
Wiring: Precautions for repair), repair the wiring otherwise replace the wiring.
Run command AC014 Alternator regulation (see Interpretation of commands).
With the bonnet closed, start the engine.
Leave the engine to run for 2 minutes at idle speed.
If the fault is still present, replace the alternator (see MR 364 or MR 370 Mechanical, 16A, Starting - Charging,
Alternator: Removal - Refitting).
AFTER REPAIRErase the faults from the computer memory, switch the + after ignition supply off and
back on again and run another check using the diagnostic tool.
USM_V48_DF012/USM_V4C_DF012
Page 69 of 94
ENGINE COMPARTMENT CONNECTION UNIT
Fault finding - Interpretation of statuses87G
87G-69V7 MR-372-J84-87G050$550.mif
UPC
Vdiag No.: 48, 4C
ET023
ALTERNATOR THERMAL FAULT
NOTESSpecial notes:
Apply the checks if the status is PRESENT with the engine running.
Switch off the engine.
Check the general condition of the alternator:
Make sure that there are no foreign bodies that could impair the alternator cooling.
Clean the alternator if necessary.
With the engine stopped, let the alternator cool down with the bonnet open for at least 1 hour.
Start the engine with the bonnet closed.
Switch on the main beam headlights and the electrical heated rear screen.
If the status becomes PRESENT again, replace the alternator (see MR 364 or MR 370 Mechanical, 16A,
Starting - Charging, Alternator: Removal - Refitting).
AFTER REPAIRRepeat the conformity check from the start.
USM_V48_ET023 /USM_V4C_ET023