Typ­i­cal BMW 1-Se­ries com­po­nents

Car Mechanics (UK) - - Electronic Diagnostics -

7 Found just to the rear of the elec­tronic throt­tle body is the mass ab­so­lute pres­sure (MAP) sen­sor. This sends in­for­ma­tion on the pres­sure within the man­i­fold to the ECU, which uses the fig­ures to help cal­cu­late cor­rect fuelling. 8 Very well-hid­den, the oil pres­sure switch (you can just see its elec­tri­cal ca­bles) il­lu­mi­nates if the oil pres­sure drops too low. How­ever, by the time the red warn­ing lamp il­lu­mi­nates, dam­age may al­ready have been done (see Prepa­ra­tion). 9 The water-cooled oil fil­ter hous­ing is very ac­ces­si­ble, be­ing po­si­tioned at the top of the en­gine. Al­ways use high-qual­ity oil fil­ters; a dodgy fil­ter may re­strict en­gine oil flow and can cause the oil pres­sure warn­ing lamp to flash. 10 The L-shaped com­po­nent vis­i­ble here just be­hind the en­gine bay’s ver­ti­cal rear bulk­head panel is the am­bi­ent tem­per­a­ture sen­sor – im­por­tant in a car with au­to­matic tem­per­a­ture con­trol. It mon­i­tors ex­ter­nal tem­per­a­tures to set the op­ti­mal in­te­rior tem­per­a­ture. 11 The bon­net po­si­tion sen­sor de­tects whether the bon­net is fully shut. If not, a warn­ing lamp on the dash will il­lu­mi­nate. Note: on newer BMWS, it is nec­es­sary to pull the bon­net han­dle twice to open the bon­net – this catches out a lot of peo­ple. 12 Vis­i­ble just left of the cen­tre of this pho­to­graph is the vari­able valve tim­ing so­le­noid for BMW’S so­phis­ti­cated VANOS valve tim­ing sys­tem. The so­le­noid em­ploys en­gine oil pres­sure to ac­ti­vate the me­chan­i­cal parts of the sys­tem to vary the tim­ing.

14 Po­si­tioned on the driver’s heel­board, but al­most com­pletely hid­den by the ac­cel­er­a­tor pedal, is the throt­tle po­si­tion sen­sor. This in­stantly sup­plies pre­cise in­for­ma­tion on the ac­cel­er­a­tor po­si­tion to the ECU, which ad­justs en­gine speed ac­cord­ingly.

17 This screen­shot of the Snap-on Verus Pro di­ag­nos­tic tool shows the fault code read­out from the en­gine ECU. There are mul­ti­ple ECUS around the ve­hi­cle and the Verus Pro can very ef­fec­tively com­mu­ni­cate with them all. 15 Pow­er­ing all elec­tri­cal sys­tems is the bat­tery, with an ex­tra (and costly) com­pli­ca­tion in the form of a fuse­board as­sem­bly. If any of the fuses blow, a com­plete as­sem­bly is re­quired (around £250 new, but sec­ond­hand units can be found, al­though they will need to be coded to the car). Don’t al­low the bat­tery to be­come dis­charged or else…

18 The Verus Pro tool shows func­tion op­tions avail­able to the op­er­a­tor, re­lat­ing to the im­mo­biliser sys­tem. Here it shows if the key is be­ing read and in­di­cates the state of the im­mo­biliser (ie, ac­tive or not), which is use­ful in a non-start sit­u­a­tion. 16 …when the ig­ni­tion key is pushed into the slot, noth­ing will hap­pen. An­other prob­lem in this area can be the lock/im­mo­biliser as­sem­bly. When you push the key, you should hear a clunk to show the ig­ni­tion lock has been re­leased. 19 An­other handy func­tion of the Verus Pro tool when used with this BMW model is that it can tell the op­er­a­tor about the qual­ity/con­di­tion of the en­gine oil. In this case, we had just changed the oil and fil­ter, so the qual­ity level was 99%. The Verus Pro can also ad­vise the op­er­a­tor re­gard­ing wear lev­els on the front and rear brake pads (the sys­tem should be re­set when the pads are re­newed). With this 1-Se­ries, the com­plete ser­vice his­tory can be recorded in the main­te­nance book and by com­puter.

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