Building the better garage
In the second part of his look at how to put together your diagnostic service offering, Frank looks at how you should always work to a plan
Published: 14 November, 2022
The most important first step begins with vehicle and owner triage. Listen carefully, ask searching and relevant questions regarding the complaint, do not accept anything until you have confirmed the condition, and never accept previous work or opinion as correct. The customer must accept this cost or walk away. The triage may include, visual inspection, road test, or a preliminary global vehicle scan, i.e., all systems. None of this is free. It is part of a progressive methodical process. Agree a separate contract for this allowing either party to walk away.
One especially crucial point to understand before you begin any repair or diagnostic investigation, you must fully understand how the system functions and the specific responsibility of each component in that system, how it operates and how to test it.
Check DTCs that are relevant to the symptoms, not forgetting pending and confirmed errors in EOBD. Also check for incomplete default flags. These cannot be cleared unless all flag parameters have been satisfied during drive cycles.
Next, you need to cross-reference specified, actual, and corrected data. A fault code will not register unless the component parameters have been exceeded, in some cases for a considerable time, so fast intermittent drive concerns may not be registered in the fault memory. Previous experience over the past 50 years has convinced me of the value in using gauges when confirming, fluid, pressure, and flow.
For example, when testing fuel pump performance, flow is just as important as pressure. Also check the pump current. It is linear with pressure, therefore faults may be predicted by checking current across the relay or fuse without accessing the pump or supply hoses.
Intermittent variable vane turbo faults are easily monitored with a gauge. We could not source suitable gauges, so I designed our own. In fact, many of our tools have been modified to suit challenging tests.
Data log selected serial data so that focused analysis can be carried out. The selected items will depend on the nature of the fault under investigation. This can then be downloaded into graphing software like datazap. If you are interested refer to my VW Amarok SCR repair article from the June issue.
There may be a technical bulletin or software update dealing with the complaint so access to the manufacturers repair information system is mandatory.
Component testing
It is at this point where component testing may commence, like each stage of an investigation there are rules that govern and guide your response. Before the output of a sensor is suspected, you must check the ground reference and power supply at the sensor. Output deviation can be caused by wiring errors, sensor error, or a genuine environment value error. It may be necessary to cross-reference the value by alternative means, where possible.
For example, with a cold vehicle, all temperature sensors will have a similar value, as will pressure sensors on a static engine. Exhaust gas temperature sensors will reduce by approximately 50°C as they pass further down the exhaust stream.
Sensors fall into set groups; Position, range or movement, temperature, pressure, angle etc.
They also fall into three output categories; Linear/analogue, digital, and sent. Because of the complexity in vehicle systems control, it is inevitable that an oscilloscope needs to be used to confirm correct functionality.
An oscilloscope, like all tools, fall into one of three groups; The good, the bad and the ugly. They demand two special skill sets; Set up and image interpretation. They provide a unique insight to mechanical and electronic functionality.
This brings me to current and ongoing problems: Accessibility, and the cost risk ratio in the diagnostic process. Many of the tools that can be used with a scope find their roots in other hi-tech industries.
Cylinder pressure analysis, WPS, is the best example. The use of an absolute pressure sensor directly in the cylinder reports real time pressure differential above and below atmosphere. With minimal component removal and the engine running, the precise valve open/close position can be established.
The catch here is fully understanding the image as correct. It may require confirmation from a good known vehicle. The other problem is variable valve lift and timing control. This will affect pressure readings and must be confirmed via serial data evaluation.
Complex
Vehicles manufactured today are a complex mixture of mechanical systems, all of which share one unique property; Mass, acceleration, and frequency. The latest technique in systems diagnosis is NVH, or vibration analysis. With the aid of a three-dimensional accelerometer and analytical software, each individual component can be identified by its frequency signature. Everything from a cylinder misfire to a defective bearing can be isolated.
Some of our more individual specialist tools include an injector test bench. This helps identify combustion imbalance from our vibration analysis. With the onset of direct drive turbo actuator control, we invested in an actuator drive simulator. Driving the wastegate through precise angles whilst monitoring the current draw confirms correct movement, range, and mechanical resistance.
It is occurred to me writing this two-part piece that several subjects identified would make good subjects for future articles, so watch this space. It has also reminded me of the remarkable skills that automotive technicians need to repair and service vehicles. Have pride in your achievements and don’t work cheap!
- Autotech Training takes the high road for Shetlands Council
Autotech Training recently sent its Business Development Director Dave Walker on a 1,600 mile round-trip to the Shetland Islands in a Autotech Training branded hybrid vehicle to help the Shetland Islands Council upskill its technicians for EVs to enable the the authority to progressively electrify its fleets of 320 vehicles.
- The safe operation of vehicle lifts
In the second part of our series from the GEA, the process of actually buying and having lifts installed is the focus
- Part two The good and THE GREAT
In part one, we looked at the start of the ‘diagnostic process.’ The first steps were customer questioning, confirming the fault and knowing the system and its function. These help the technician to build the ‘big picture’ necessary to repair the vehicle correctly.
In this article we will look at the next four steps.
Step 4: Gather evidence
It is easy to overlook this step as many technicians think of it as the overall ‘diagnosis.’ However, once the technician understands the system, gathering evidence will provide key information. This step is normally best carried out with the use of test equipment that does not mean the dismantling of systems and components.
Many technicians have their own favourite tools and equipment but this list can include (but not limited to)
the following:
Scan tool – It is always best practice to record the fault codes present, erase the codes, and then recheck. This means codes which reappear are still current. Remember that a fault code will only indicate a fault with a circuit or its function. It is not always the component listed in the fault code that is at fault
Oscilloscope – An oscilloscope can be used for a multitude of testing/initial measuring without being intrusive. Some oscilloscope equipment suppliers are looking at systems within high voltages hybrid/electric vehicle technology. The waveforms produced by the test equipment can be used when analysing the evidence and may indicate that a fault exists within a system. An understanding of the system being tested will be necessary to understand the information. This may even include performing sums so all those missed maths lessons at school may come back to haunt you. It may take time to become confident analysing the waveforms, so be patient
Temperature measuring equipment – This can include the use of thermal imaging cameras. Most systems that produce energy/work will also produce some heat. The temperatures produced vary from system to system. Examples include everything from engine misfires to electrical components, as well as air conditioning system components and mechanical components such as brake and hub assemblies. The possibilities are endless and results can be thought provoking.
Emission equipment – By measuring the end result, an exhaust gas analyser can show you if the engine is functioning correctly. The incorrect emissions emitted from the exhaust help indicate a system fault or a mechanical fault with the engine
Technical service bulletins – Many vehicle manufacturers produce technical service bulletins (TSBs) that are generated by a central point (usually a technical department) from the information that is gathered from their network of dealers. Some of these may be available to the independent sector either through the VM or through a third party – It’s always worth checking if these exist. They may indicate a common fault that has been reported similar to that the technician is facing. Some test equipment suppliers may provide TSBs as part of a diagnostic tool package
Software updates – Many vehicle systems are controlled by a ECU. Most vehicle manufacturers are constantly updating system software to overcome various faults/ customer concerns. Simply by updating the software can fix the vehicles problem without any other intervention of repairing a possible fault. This is where having a link to a vehicle manufacturer is vital in repairing the vehicle
Hints & tips – Most technicians will have a link or access to a vehicle repair forum where they can ask various questions on vehicle faults and may get some indication of which system components are likely to cause a vehicle fault
Functional checks – Vehicle systems are interlinked and typically share information using a vehicle network. The fault may cause another system to function incorrectly, so it is vitally important that the technician carries out a functional check to see if the reported fault has an effect on another system. By carrying out this check the technician again is building the big picture
Actuator checks – Most systems today are capable of performing actuator tests. The technician can perform various checks to components to check its operation and if the system ECU can control the component, often reducing the time to the diagnosis, by performing this task the technician can identify whether it is the control signal, wiring or component or it is sensor wiring. This function can be used in conjunction with serial data to see how the system reacts as the component functions
Serial (live) data – The technician can typically review a vehicle system serial data through a scan tool. Having live data readings to refer to can help you review the data captured. Using actuator checks and viewing the serial data can also help the technician to identify a system fault
Remember to record all the evidence gathered so it can be analysed during the next step in the diagnosis. We can’t remember everything. If the technician needs to contact a technical helpline they will ask for the actual readings obtained recoding the data gathered will help.
Step 5: Analyse the evidence
Analysing evidence gathered during the previous steps can take time. The technician needs to build the big picture from all the evidence gathered during the first few steps. You need to analyse the information gathered, and decide on what information is right and wrong.
This step may rely on experience as well as knowledge on the product. You should take your time – don’t be hurried. Time spent in the thinking stages of the diagnosis can save time later. Putting pressure on the technician can lead to errors being made. It may be necessary to ask the opinion of other technicians. If the evidence is documented it may be easier to analyse or share between others.
Step 6: Plan the test routine
After analysing the evidence gathered it’s now time to start to ‘plan’ the best way to approach to the task or tasks in hand.
The technician should plan their test routine, decide on what test equipment should they use, what results are they expecting, if the result is good or bad and which component should they test next.
Document the plan – this enables you to review decisions made at this stage in the next step. The technician may not always get it right as there may be various routes to test systems/components. The test routine may have to be revisited depending on the results gathered during testing. Documenting the test routine will provide a map. Also, don’t forget to list the stages, as this is something that could be incorporated into an invoicing structure later.
The technician should indicate on the routine what readings they expect when they carry out the system testing. This can be generated by their own knowledge/skill or the expected readings may come from vehicle information which they have already sourced. If the information is not known at the time the test routine is planned, then the test routine may highlight what information is required and what test equipment is needed. You shouldn’t be afraid to revisit the plan at any time and ask further questions on which direction the tests should take. If the plan is well documented and the technician becomes stuck at any point, they can pause the process and revisit later. Also the information can then be shared with various helplines that support workshop networks.
Step 7: System testing
The technician then follows their pre-determined plan, if it is documented they can record the results of the test(s) as they follow the routine.
Many technicians tend to go a little off-piste when they get frustrated. Having the routine documented can keep the technician on track and focused on the result. If the routine is followed and the fault cannot be found the technician may have to go back to the analysing the evidence or planning the test routine. The technician shouldn’t be scared of going back a few steps, as I said previously analysing the evidence takes practice and can be time consuming, not to be rushed.
Summing up
Remember to follow the process. It is easy to be led off track by various distractions but don’t try to short circuit the process. Some steps may take longer than first thought to accomplish than others. Some distractions may be outside of your control, and it may be necessary to educate others. Practice, practice, practice. Refine the process to fit in with your business and its practices, the business could align its estimating/cost modelling to the process, being able to charge effectively and keeping the customer informed at each stage of the process.
Coming up...
In the next article I will be looking at the next four steps which are; Step 8: Conclusion (the root cause), Step 9: Rectify the fault and Step 10: Recheck the system(s). The last article in this series will indicate the final three steps and how to fit them all together in order to become a great technician and perhaps succeed in Top Technician or Top Garage in 2018.
- Brexit and BER: IMPACT
What are the possible outcomes of Brexit for the UK aftermarket and should we be concerned?
- No codes, no clues?
Have you ever had a car in with a running fault or an issue, and you plugged the diagnostic tool into the OBD socket then read for trouble codes, only to be met with the message ‘no faults stored’?
For many reasons, this confuses technicians and stops them being able to progress with the job. They have no clues or starting point to work from. However, many other tests can be done to find the root cause of the issue. I have worked with many a technician who has been lost after finding a ‘no fault found’ message. I recently had a job where I was able to demonstrate to my colleague how knowing some numbers and how systems work and interlink can help identify what is wrong.
Call-out
The vehicle in question was a 2012 Land Rover Discovery 4. As we specialise in LR we have built up a good reputation in the area for being able to fix them, having also invested in dealer tooling and information. The customer’s first contact with us was via telephone and he explained he had parked the vehicle up outside his house and then having come to it the next day it would not start. The engine would turn over but it would not fire into life. He informed us his local garage had come out for a look and had been unsuccessful in finding the cause and recommended getting the vehicle recovered to us. He asked our call-out charge and asked for us to come and take a look before he organised recovery. This is not my favourite type of job as with limited tooling there is only so much you can do but we agreed to go and take and look and see what we could find.
No fault codes stored
Along with my colleague Jamie we went to the customer’s house that afternoon, taking a scan tool and the tool kit in our work van. Once we arrived we spoke to the customer to gather some information about the problem. He told us no recent work had been carried out on the vehicle and the other garage had done some basic tests on the battery and fuel system where it sat but could not find an issue. I sat in the vehicle and cranked the vehicle to verify the complaint, doing this also allowed a few checks to be done by listening to the sound of the engine cranking. A trained ear can pick up a compression issue, whether it is spinning fast enough or anything mechanical which doesn’t sound correct.
On this vehicle though all sounded ok. I then let Jamie do some checks to see what he could find. As a younger technician he mainly does MOT and general service work, so it was a good opportunity to possible teach him something along the way without the distraction of a busy workshop. After some basic checks he decided to plug in the scan took and see if any fault codes were stored. Upon carrying out a fault code report he was met with the message ‘no fault codes stored’. I then asked him what his thoughts were and where we go next. His reply was “I don’t know?” I am sure this has happened to some of you reading this article, we have all been there.
Live data
I explained to him that live data was a key element here and we should use it to our advantage. We need to look for data relevant to the complaint to rule out what it can’t be, and knowing what the numbers mean will do this quickly. Unfortunately, this takes years of looking at good data, taking notes and memorising it. Luckily for him, I was able to assist. My first checks were to be engine RPM, fuel pressure, immobiliser status, cam/crank synchronisation and a plausibility check of all temperature and pressure sensors to make sure they were in spec. Working through them all with ignition on, then cranking everything looked good so the engine should start but why wouldn’t it? This is where it pays to step back for a moment and evaluate what you know already and what you should do next.
Smoke/air pressure
An engine in its simplest form is an air pump. We know it needs compression, fuel and air to run. With what seemed to be good compression, and from what I had heard, also good data from the scan tool, with limited resources, I decided the next test would be to see if any smoke was being emitted from the tail pipes. This would show if there was any sign of fuel delivery to the engine. With good RPM and fuel pressure, if the ECU is happy, it should be firing the injectors. There was no smoke, however when I felt the tail pipes there was no air pressure whatsoever from either tail pipe. Was this a clue to where the issue may lie?
My first thought was we have a restriction and the engine cannot breathe, so we are missing the air section of the triangle for the engine to run. I then had a good visual inspection of the engine. Knowing the design well, I decided to open the inlet up to atmosphere by removing the map sensor to see if there was any change. If there was a blockage, this test would prove it and allow the engine to run. In this vehicle, the engine is a V6, so it uses a conventional V configuration. To allow air to flow into both intakes of each bank there is what Land Rover call an intake throttle manifold which also houses the MAP sensor, the EGR inlet pipework and a throttle butterfly flap with a rubber hose to direct air from the intercooler into the manifold (fig1). Removing the MAP sensor would allow air to be released if there was an issue from either EGR valve or upstream from the intake i.e. throttle butterfly, failed turbo just to name a few. On removing the sensor and cranking the engine it now fired into life and idled fairly well, this confirmed we had a blockage somewhere manifold side starving the engine of air.
Throttle butterfly flap
Checking the clock, we still had some time left allotted for the call out. I decided as it was easy to remove the intake hose to the intake throttle manifold just to see as a quick test if the issue was before or after. Upon removing the pipework and refitting the map, the engine no would not start, again proving the issue was on the engine side of the pipework. Removing the air intake plenum to the throttle manifold then revealed the issue. The throttle butterfly flap used to strangle the engine of air on shutdown had jammed shut and never reopened as the housing was heavily covered in carbon. This butterfly, when working correctly, should spring back open ready for the next engine start. Questioning the customer and his driving style revealed he mostly done slow speed and town driving and used supermarket fuel, all of which were a contributing factor to the issue as the valve sits closely to the flow of EGR gas from both valves. Forcing the valve open and refitting the components allowed the vehicle to be driven back to the workshop for a repair to be carried out.
Upon the removal of the entire assembly (fig2), it was found the unit would be better to be replaced as cleaning would not remove all of the carbon deposits and could cause the issue to re-occur. The EGR pipework was also removed and cleaned as a preventive measure along with an oil and filter change and the vehicle was returned to the customer.
Further learning
Why were there no fault codes stored you ask? Well on this engine the position off the butterfly flap is monitored and it should have stored a stuck closed fault but this may not be part of the software’s strategy so I am unable to answer why. However, this article shows that if you have an issue and no faults are stored, there are tests you can do to find the issue. So next time you have a scan tool connected, grab for example 10 good live data PIDs and store them then learn them off by heart. Once you have mastered that section move onto some more and soon you will build up a good mental library of what good data should be, which helps massively to fix cars!
