Di­ag­nos­tics Doc­tor

Car Mechanics (UK) - - Contents -

Q This is not specif­i­cally a di­ag­nos­tics prob­lem, but it needs your ex­per­tise. I have read in CM about prob­lems that arise if you switch off the en­gine while the diesel par­tic­u­late fil­ter (DPF) is re­gen­er­at­ing. Is there a way of know­ing when a re­gen is tak­ing place on an Audi 3.0 TDI to avoid this happening? The first is my 2011 Audi A7 (en­gine code CLAB) and the sec­ond is my wife’s 2014 Q5 (en­gine code CDUC). I was think­ing of at­tach­ing a bulb or LED to a live wire which trig­gers the DPF re­gen ac­tions. Have you any idea where I should start look­ing? Shabaz A You shouldn’t need to go to such lengths as both of your Audis are fit­ted with a built-in warn­ing sys­tem for the DPF. When the ve­hi­cles be­gin the re­gen­er­a­tion process, the warn­ing lamp on the dash will il­lu­mi­nate, dis­play­ing the mes­sage: ‘Par­ti­cle fil­ter see owner’s man­ual’. An au­di­ble warn­ing will also sound to alert the driver. When this oc­curs – which should only be when the en­gine is at op­er­at­ing tem­per­a­ture – you need to drive the ve­hi­cle at a min­i­mum speed of 40mph for at least 15 min­utes, en­sur­ing the en­gine speed re­mains at ap­prox­i­mately 2000rpm. This can be done by us­ing fourth gear if the car is a man­ual or by se­lect­ing ‘Sport’ in au­to­mat­ics. The warn­ing lamp and mes­sage will go out once the re­gen­er­a­tion has been com­pleted.

A forced re­gen­er­a­tion can be car­ried out us­ing di­ag­nos­tic equip­ment, so if the warn­ing light and mes­sage do not clear, this op­tion should be used.

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