Car Mechanics (UK) - - Elec­tron­ics Doc­tor -

Symp­toms in­clude en­gine mis­fir­ing, rough run­ning and pos­si­bly a smell of un­burned fuel. The fault lies with the pen­cil coils and the trou­ble usu­ally starts with an oc­ca­sional cough from the en­gine. It’s only when a coil fails com­pletely that the car will be­come un­drive­able, and be­cause of the en­gine set-up it usu­ally takes out two cylin­ders at once, ie, cylin­ders 1 and 4 or 2 and 3. You will cer­tainly find a trou­ble code stored: ‘P0301’ denotes cylin­der

1, ‘P0302’ is cylin­der 2 and so on. If pos­si­ble, a full di­ag­nos­tic check should now be car­ried out, but be aware that cylin­der 1 on Re­naults is on the gear­box side. If no di­ag­nos­tic tool is avail­able, a quick check can be to dis­con­nect each cylin­der in­jec­tor in turn and lis­ten for a change in the en­gine tone.

The coil is held in place by ei­ther a 10mm bolt or Torx bolt. Be care­ful when re­fit­ting these: they should only

be done up hand-tight and the threads strip eas­ily. If the threads do strip it’s a night­mare to get to them.

It’s al­ways worth re­new­ing ALL the coils at once as they are very cheap and usu­ally fail quickly, one af­ter the other. It goes with­out say­ing that it is also wise to re­place the spark plugs at the same time.

Note that a plug and coil cov­ered in oil in­di­cates a worn cam cover gas­ket; this should be re­newed at the same time.


When our next fault arises, the en­gine may in­ter­mit­tently refuse to start, only to fire up at the next at­tempt. Un­for­tu­nately, there is no set no pat­tern as to when the car will or won’t start! This frus­trat­ing fault can be dif­fi­cult to

di­ag­nose and it’s hit-and-miss whether a di­ag­nos­tic fault code will be stored, but you might get a code re­lat­ing to the crank­shaft sen­sor or en­gine speed sen­sor. A quick test is to lo­cate the crank sen­sor above the gear­box, wig­gle the wiring and then try to start the en­gine. Dodgy wiring to the plug is a com­mon prob­lem, but the crank­shaft sen­sor it­self can also fail – it’s held in place by two 10mm bolts, but be very care­ful when re­mov­ing it so that it doesn’t fall in­side the gear­box.

If you have an ap­pro­pri­ate di­ag­nos­tic tool, an­other test is to look at the live data and check for an rpm sig­nal, which will put you in the right area.

There is a mod­i­fied sen­sor and con­nec­tor that needs wiring in with a new plug. The kit comes with a crimp­type con­nec­tor, but we have found in the past that it’s best to sol­der the con­nec­tions be­cause the crimp-type can cor­rode around the joint. It is also rec­om­mended that a good spray wax or sil­i­cone pro­tec­tant is ap­plied af­ter­wards.

A new sen­sor/kit is read­ily avail­able at all mo­tor fac­tors, but avoid cheap or poor qual­ity brands.


This ail­ment isn’t ex­clu­sively a Mé­gane fault but some­thing that plagues all Re­naults of this era. As with the ig­ni­tion coil fault, if a car has been owned for more than just a very short time, the owner/op­er­a­tor is very likely to have suf­fered from this.

The fun­da­men­tal prob­lem lies with the elec­tric mo­tor, which has a habit of fail­ing out the blue, with the re­sult that the win­dows get stuck in the ‘down’ po­si­tion.

For­tu­nately, re­mov­ing the door panel to gain ac­cess to the elec­tric mo­tor is sim­ple, al­though the panels are held on with Torx screws and some in­fu­ri­at­ingly poor qual­ity plas­tic clips which gen­er­ally break when re­moved. A new mo­tor is read­ily avail­able from af­ter­mar­ket parts sup­pli­ers, and it’s not re­ally worth pay­ing ex­tra for a gen­uine Re­nault part.

An­other an­noy­ing prob­lem is a trou­ble­some hazard lights switch. These fail in­ter­nally and when the switch is pressed, noth­ing hap­pens. This fault re­quires the fit­ting of a new switch and af­fects the en­tire Re­nault range.

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