Dirty work: Keeping diesel exhausts clean

Diesel vehicle exhaust systems can run clean if they are given the proper care, and vital components like the DPF are properly serviced
Published:  11 October, 2017

The exhaust is a lot more than just an exit route for waste gases for some time now. Tim Howes, deputy general manager – supply chain and technical service, NGK Spark Plugs (UK) Ltd, provides some context: “In 2009, The Euro V emissions standard for passenger cars demanded a significant reduction in NOx, HC and particulate matter and in 2014 the Euro VI standard brought a further tightening of these emissions, primarily for diesel engines.”


Complexity
For diesel powered vehicles this has meant a significant increase in the complexity of exhaust gas recirculation (EGR) and after treatment resulting in the fitment of various combinations of diesel oxidising catalyst (DOC), selective catalytic reduction (SCR), lean NOx trap (LNT),  diesel particulate filter (DPF) and other associated devices and control systems.
All these additional components have led to an increased need for sensors in the system.


Spin the wheel

Frank Massey looks at how you need to approach a problem when different types of sensor are involved
Published:  09 October, 2017

I have been asked several times about ABS wheel sensors. Like many other components, the technology is changing. The changes reflect the expansion in integrated chassis dynamics.

Just imagine how many functions require wheel speed and rotational differential data.

ABS, dynamic stability, hill start, audio volume, navigation, self park, all wheel drive, active steering assist, electronic handbrake etc. Sharing this data on a high speed can network ensures very accurate vehicle motion dynamics.

Older variable reluctance sensors (VRS) rely on a coil generating an alternating voltage when rotation occurs. The problem is they are not directional sensitive and cannot report motion at very low speed. Air gaps were critical as they affect signal amplitude. They are often referred to as passive sensors. So, the introduction of digital or active sensors was inevitable.


Principles
How do we tell them apart? Active sensors require a voltage supply from the ABS PCM, with a ground or signal return. They operate with different principles of signal generation; hall, and magneto resistive. Pure hall effect sensors will switch between the supply potential voltage and ground. Magneto resistive sensors operate on the principle of current and voltage change in response to a change in magnetic induction. This change can be introduced in several ways reflected in wheel bearing and sensor design. Smaller sensors with integrated magnetic field rings are now the norm. Developed by NTN at their Annecy facility they are called encoded bearings. A small ring mounted at one end of the bearing carries a series of north south poles. These have now been replaced by dual encoding, two sets of magnetic rings with a unique offset. This enables the abs module to determine direction of rotation.


Subtle differences
There are two very subtle differences in the digital outputs. They can be called pull up or pull down. The sensor supply voltage will be slightly lower than battery voltage this is due to the different internal resistance values. However, it will be around 10.5/11.5v.

The ground or return signal value will vary between 0v or 1.4/1.8v. You could have a sensor or circuit fault; let me try and explain the subtle differences, and how to prove which is which. Remember the golden rule if in doubt compare a wheel circuit that works normally.

First unplug the sensor and measure both circuits in the loom. With no load applied the supply voltage should jump up to NBV

Next check the ground circuit if its true ground then it’s a pull-down type and the signal will be on the power line, and may only be around 200mv

If a small voltage exists then it’s a pull up type and the signal will be on this wire not the supply. The digital signal will be very small when the wheel rotates. It could be small around 200/400mv, or as high as 0.5/1.8v, depending on the manufacturer variant

Common sense would dictate the serial route is easiest, however how would you determine an intermittent fault? It could be a faulty sensor, faulty encoder, or a circuit error. The only way is using a scope. Should we measure voltage or current though? Both change in the circuit. Unless you have a very special current clamp, go for voltage and select a AC coupling.

The specific question I am often asked is current measurement, well I can tell you in a pull-down circuit its around 7-15 ma with a 400mv voltage change. The pull up type will produce around 6/13ma with 0.2/0.35mv.     However, these voltage values can vary due to the value of the two parallel internal sensor resistors these are normally 1.4k ohms, with a much higher resistor in the meg ohm range, within the ABS pcm.

I hope this helps. The pico image was taken from a VW Golf 1.4 TSI. The easy bit is replacing the wheel sensors. Ever since metal housings were replaced with plastic they never corrode in the housings
do they…?


Electric future shock

Here we take look at the many challenges the independent garage sectors faces in an increasingly electric future
Published:  05 October, 2017

The need to adapt to changing vehicle technology is one of the main challenges of our time in the sector. Increasing connectivity and a vastly more complicated conventional vehicle provide a whole raft of obstacles on their own, before you even get to the rise of electric vehicles and hybrids.

Add to that a more uncertain legislative environment resulting from rules not quite keeping up with the technology coming in, and you’ve got yourself a whole host of issues that the entire industry needs to stay on top of if it is going to continue to offer a sterling service to customers.

Let’s look at electric vehicles. For Tom Harrison Lord from Fox Agency, the b2b marketing company specialising in the automotive sector,  Automechanika Birmingham offered a troubling glimpse into the future:  “This summer’s Automechanika Birmingham was entertaining and enjoyable as ever, but it also exemplified a worrying trend in the motor industry today. With the advancement of electric vehicles, there are going to be some rapid and stark changes ahead. The automotive aftermarket, however, seems to be burying its head in the sand.”


Access
The key, as it has been in the past, is access. In this case, the right to be able to repair vehicles. Think that’s all sorted? Perhaps not:  “The rise of the electric cars and vehicles is something that could hit the automotive aftermarket hard – in particular, independent garages.

“Many, if not all, electric vehicles invalidate their manufacturer warranty if essential work is carried out on the electrical systems by someone other than the main dealer. What’s more, many cars with batteries, such as the Mitsubishi Outlander PHEV, have warranties on the electrical components lasting up to ten years.

“Having no choice but to use the main dealer for a full decade shows just why independent workshops will have fewer vehicles coming through the doors in the years ahead.”


Agile Diagnostics

Published:  17 September, 2017

Barnaby Donohew examines how the aftermarket can learn from the tech sector to improve diagnostic outcome


Fighting through to a solution

Published:  20 September, 2017

Do our own workshop war stories point to a diagnostic way forward asks  James Dillon


The happy camper

Published:  13 September, 2017

It’s only when you visit the past that you realise how far the journey to the present has taken us. Some time ago Martin, a very good friend of mine from Londonderry, sent over a set of very early EVL Bosch injectors.

This injector pattern started life around the late 1960s and ran through to the mid 1980s and was used by Ferrari, Volvo, Opel, and many others. The set supplied to me came out of a VW camper van, and like many from this era were badly rusting and contaminated from in-tank corrosion. At the time fuel lines and tanks were made from untreated mild steel, and filtration did not meet current standards of 5 microns, or 2 microns with the latest HDEV 6 injectors. The biggest single cause of wear and failure was water ingress in gasoline due to condensation and external ingress.

The injectors were in a bad condition, sticking, blocked, and dribbling. I started the cleaning process with an external pre-clean ultrasonic tank before risking contamination in our ASNU bench. Several cleaning sessions later, with a varying degree of improvement, we arrived at a fully serviceable set.

I posted them back assuming it would be the last of my involvement. I should have known better. Martin and Matthew at Conlon motors have been involved with our training programme over many years. I travel over there several times a year for onsite training, and you have guessed it, waiting for me on my last visit was the camper van.

It was running extremely rich, blowing blue smoke. You could taste the emissions. If you have ever followed a vintage car you will know what I mean. This is where a trip down memory lane started.  I have not worked on this system for many years.  In fact it was on systems like this that our current-day diagnostic processes were developed.


There’s no substitute for experience

John Batten explores what it takes to give your business the competitive advantage
Published:  01 September, 2017

Our industry is in a constant state of flux; new technology and changing customer behaviour are impacting our organisations, and ultimately the financial success of your business.


Challenging current techniques

Published:  18 July, 2017

Frank Massey looks at how you need to always keep an open mind on diagnostic methods


Under pressure

Published:  18 May, 2017

Even apparently simple problems require thorough investigation if you want to diagnose faults right the first time


The future of DPF servicing

Change can seem shocking at first, but is it the future?
Published:  08 May, 2017

Two months from now will bring my tenure in the motor industry to 49 years. I would like to think I have evolved, kept up with technology, enabling me to provide a professional service, enjoying customer respect and integrity. My focus has been the technical challenges, while my son David manages the commercial responsibilities.


Let go of my Lego

James looks at how the interconnected car can cause you headaches
Published:  03 May, 2017

"Electronic Lego" is a phrase that was introduced to me by an engineering manager when I worked for the diagnostic company Crypton around 25 years ago. In the late 1980s the Company had developed engine tuning machines which moved away from bespoke central processing units (the so called Big Box tuners) to a PC based system. The elements of the PC based system could not just be bought and fitted together (like lego) and be expected to work. The PC components and peripherals had to be carefully selected, including the compatibility of their drivers and software to ensure a robust PC based diagnostic machine could be created. Over the past 10 years or so motor vehicles have moved away from their previous Lego like construction, where replacement parts were free to be plugged in and replaced at will. The change was due partly to the modern vehicle being constructed as a rolling network of computers and partly to the advent of the factory fitted immobiliser, where transponder keys and the relationship between vehicle computers became prevalent.


Beat the clock as Top Tech moves up a gear

Did you pass the first quiz? Then it’s time for round two
Published:  04 April, 2017


Reasoning and diagnostics Part II

In this issue, Barney Donohew explores critical thinking
Published:  13 March, 2017

We began this journey last issue, so to recap: We need solid reasoning skills to carry out effective diagnostics; persistently good decision making doesn't happen by chance. Possibly out of convenience these skills are often underestimated and undervalued by people, both in and out of the trade. We must raise awareness of the discipline and precision of thought necessary for logical and critical thinking: so we can be better rewarded for our efforts; and to make sure they are consistently and properly applied.

Reasoning, arguments and hypotheses
We covered some fundamentals in my last article: we explain our reasoning using arguments, which contain statements supporting a conclusion; one type of argument, a deductive argument, should guarantee the truth of its conclusion (if it is sound); however, we need to use critical-thinking to check this, by making sure i) there are no other possible conclusions (which makes it a valid argument) and ii) the supporting statements are true.


Reasoning and Diagnostics Pt 1

Barney Donohew explores logical and critical thinking
Published:  17 February, 2017

Diagnostics is all about decisions. And what is a decision? It is a conclusion or resolution reached after consideration. Therefore, efficient and effective diagnostics is about drawing the right conclusions at the right time. How do we do that? Amongst other things, by making sure our logical and critical thinking skills are up to scratch. This series of articles aims to help us with that by looking at the principles of human reasoning.


The Tools for the job

Frank Massey looks at creating your own tools and methods
Published:  01 May, 2017

I gave this topic some considerable thought before choosing to discuss not just a selection of tools we use, but also some tools we have designed and modified.


ABS feature

David Hirst looks at troublesome Teves Mk60
Published:  27 January, 2012

Peeved with the Teves?


A boost in sales

BTN Turbo explains how the market is growing as manufacturers realise their efficiency
Published:  06 March, 2015

BTN Turbo


It's diagnostics Jim, but not as we know it

First Contact or the Final Frontier?
Published:  19 April, 2017

By James Dillon


Combustion failure

Misfire when ready - Causes for combustion failure
Published:  12 April, 2017

By Frank Massey


Teasing you with the TCU

What to do when the transmission control unit goes faulty?
Published:  05 April, 2017

By ACtronics


A bewitching tale

Frank Massey explains how a fixed problem isn't always the solution
Published:  06 June, 2016

A couple of interesting workshop repairs have taken my fancy in the recent months, the first involves a BMW 530 common rail diesel.


Reading between the lines

A lacklustre Freelander is sorted by delving into the not-so-obvious data
Published:  04 October, 2013

If you've been reading this magazine for any amount of time, you'll be well aware of the obvious benefits of using an oscilloscope when diagnosing faults, but it is the less obvious benefits that with practice can lead to the correct diagnosis.


Access OE repair data

Technical data straight from the manufacturer
Published:  28 November, 2014

Alldata Repair gives independent workshops direct access to OE repair information via an online portal. The data is unedited - diagrams are not re-drawn and the info is uncut, what you see is the same information available to techs within dealer workshops.


Keeping the code

The Garage Equipment Association revised its 'code of conduct' for both its members and engineers earlier in the year. We caught up with head man Dave Garratt to find out how it will affect your MOT centre
Published:  09 September, 2013

Q: Why did you feel there was a need to review your code of conduct?



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