Car Mechanics (UK) - - Project Mercedes-benz E320 Cdi -

u I have a few com­ments re­gard­ing your

Elec­tronic Di­ag­nos­tics fea­ture about the VW Golf 1.6 FSI (CM, Au­gust 2017). I was con­fused by your say­ing the car was fit­ted with a BLP en­gine. With the Golf MKV, the BLP en­gine was only fit­ted for the 2005 model year, specif­i­cally from May 2004 to July 2005. As the sub­ject car was a 2008 model, it could not have a BLP en­gine. I sus­pect it was prob­a­bly a BLF en­gine. Al­though the two are closely re­lated, there are a num­ber of im­por­tant dif­fer­ences, such as the BLP hav­ing the very fail­ure-prone and ex­tremely ex­pen­sive com­bi­na­tion NTK brand NOX sen­sor. Also, the BLP en­gine uses 98RON fuel as a min­i­mum, whereas the BLF can use 95RON.

This gen­er­a­tion of Golf ECU uses the Bosch Motronic MED 9.5.10 man­age­ment sys­tem. The des­ig­na­tion 03C 906 056 EM quoted in the ar­ti­cle is the VAG part num­ber.

The brake pedal op­er­ated switch is a dual pole unit which sends two sep­a­rate sig­nals, one to the ECU and the other to the brake light in­put of the on­board sup­ply con­trol unit and the ABS pump ECU. These two sig­nals must be de­tected to­gether or the ECU drops into safety mode. If the ECU in­put fails, the brake lights will still work.

You say that if the bon­net switch fails in the open po­si­tion it will stop the wipers from op­er­at­ing (they do work af­ter around 20mph, though), but the switch is also linked to the in­stru­ments, not just for an open warn­ing but also be­cause it works with the oil level de­tec­tion sys­tem to in­di­cate if the bon­net has been opened af­ter a low-level warn­ing.

The in-tank lift pump gets a men­tion, but not the prob­lem­atic high-pres­sure pump mounted on the cam cover.

A fast way to tell if a mis­fire is due to a burned ex­haust valve is to clear the codes with the en­gine run­ning. If the mis­fire clears for a while, this shows that it is the ECU shut­ting down the in­jec­tor on a cylin­der that it has de­tected as pro­duc­ing ex­ces­sive emis­sions. This is a use­ful quick test if buy­ing a ve­hi­cle with a prob­lem should a com­pres­sion check not be prac­ti­cal.

The pre-cat Bosch LSU-4.9 wide­band sen­sor and the post-cat Bosch LSF-4.2 nar­row­band sen­sor on the BLF en­gine can be tested us­ing a di­ag­nos­tic sys­tem that is ca­pa­ble of ac­cess­ing the Ba­sic Set­tings func­tion of the ECU in data groups 028 and 030 up­wards. This is a very ef­fec­tive way of check­ing your work – it is known as ‘set­ting the Readi­ness Code’.

The Golf MKV has a unique and overly com­plex door de­sign where ac­cess­ing the in­ter­nals means the skin must be re­moved. To do this, the door has to be open. In the event of the door lock unit not op­er­at­ing, tak­ing off the in­te­rior door panel with the door closed is al­most im­pos­si­ble with­out dam­ag­ing the door­card’s for­ward mounts and you will be sorely dis­ap­pointed to be con­fronted by a sheet of metal! Open­ing one of these doors when jammed is one of the big­gest prob­lems I have ever en­coun­tered in 33 years of work­ing on VWS. Thank good­ness they changed back to a con­ven­tional de­sign on the Golf MKVI! Steve C

Mar­tyn Knowles re­sponds: Thanks for the ad­di­tional info, Steve. We did get the en­gine code wrong on this oc­ca­sion. The 2008 car we di­ag­nosed does have the BLF ref­er­ence. Also, only half of the cir­cuit di­a­gram for the Motronic MED man­age­ment sys­tem was printed. We’ve re­pro­duced the di­a­gram in full on page 80.

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