Fig 1.
Common people
Diagnosing a common fault is not as simple as it might seem; You need to test as if you are seeing it for the first time
Fig 2.
Published: 01 December, 2021
How do you go about diagnosing a common fault that you have seen before and all the symptoms match? Do you go ahead and fit that new part with no testing? Do you go straight to where you think the issue will be or do you test to be sure regardless of the situation?
You may or may not recall several articles ago, in the May 2020 issue of Aftermarket, I had a Land Rover Discovery 3 which would not start after being jump-started incorrectly and was fixed by reflashing the engine control unit software. Well, strangely enough, I was recently presented with a Range Rover Sport with near enough the exact same initial symptoms and fault codes. I want to show how starting afresh and testing, instead of jumping to the same conclusion, prevented a misdiagnosis.
Customer complaint
The customer’s complaint was that the vehicle would crank over but would not start. They said previously that the vehicle had started showing an intermittent no-start condition after sitting for a short period of time, for example to go into a shop. Once they returned, the car would crank and not start. The customer had discovered though that if they then waited five minutes and tried again, the vehicle would then start and be okay for the rest of the day. However, by now the symptoms had slowly become worse and no amount of cranking would start
the vehicle.
As always in my diagnostic process, the first step is to confirm the customer complaint and look for any tell-tale clues along the way. Yes it seems silly on the face of it to crank the engine over knowing it will not start, but an experienced technician may pick up a clue which will give direction where to go next so it always pays to always confirm the complaint. On this occasion confirming the complaint revealed no clues so it was on to the next step and to check for fault codes and review some live data.
Multiple fault codes
As can be seen in Fig.1, we have multiple fault codes stored for all different circuits and systems on the vehicle so where do we start? As in previous articles I have written, I always like to split them up into a list and put the most likely causes at the top and start there. Looking at the list we have five fault codes and I felt three could cause the no-start.
There are a number of likely causes. It could be a lack of fuel pressure, as the fault code states it is too low. The DC/DC converter fault also is another clue, as this converts the 12V supply from the battery and boosts it up to 60/70v to open the fuel injectors. The fact that code is stored could be another reason the engine will not start and the system voltage low fault code as this could indicate the control unit isn’t receiving the voltage it should to operate correctly.
The other two fault codes I felt could be put to the bottom of my list. An EGR fault most likely would not cause a no-start issue on this particular engine and there are two fitted due to the the engine being a V configuration. Having plenty of experience with this engine, I have seen many stuck open and closed EGR valves not cause the customer’s complaint due to the pipework configuration so it could be ignored for now. Lastly, there is the control box fan fault. This is a small fan mounted next to the engine ECU to control its temperature and would also not cause a no-start complaint.
Live data
My next step was to consult live data and look at module voltages and fuel pressure as these were at the top of my list. Cranking the engine while monitoring rail pressure showed there was next-to-no fuel pressure being generated, so this is one of the reasons the engine will not start. In that case, why do we have a low system voltage code and a DC-DC converter fault logged? With reference to Fig.2, looking in the module voltage section in live data showed why we have 0v for battery voltage and 3v for the DC-DC converter. As I mentioned, this should be around 60-70v on this particular vehicle so this explained the reason for the other fault codes. I then decided to pull up a wiring diagram and look at how the engine ECU was supplied power to formulate a plan of attack for these faults.
Test plan
The main power supplies were from several fuses in the engine bay fuse box, most of which were fed power when the engine control relay was energised. This also then turned on the fuel pump relay and allowed the low-pressure fuel pump in the tank to operate. I now had information to write up a test plan. My plan was to check low fuel pressure as it was easily done by a Schrader valve on the top of the engine. If there was nothing I could now be confident to test the fuses for power and the engine control relay and the fuel pump relay for correct operation as these items linked all my faults together. Upon connecting a gauge to the fuel system and turning on the ignition, I had no fuel pressure coming from the tank, so I was happy to now test at the fuse box. I checked the fuses which were supplied power from the engine control relay and all had nothing, so I moved onto the engine control relay. Upon touching the relay to remove it to test its inputs, a click was heard and the engine started to buzz indicating there was power being supplied to components. A quick circuit check showed the relay to be faulty and intermittently latching correctly internally so a new relay was fitted and the system retested. I now had power at all the fuses required and the low fuel pressure was now correct as the in tank pump was being energised. Looking to Fig.3, a check of live data now showed the correct voltages. A fault code clear was then done and upon cranking the engine it now fired into life, with only the EGR fault code remaining. After some checks this was found to be seized. The vehicle was then rebuilt and handed back to the customer.
Starting fresh
To summarise, a faulty relay caused all the problems. Having seen similar fault codes on the previous vehicle I mentioned, it would have been very easy to go down the same path.
However, starting fresh and applying methodical thinking and a plan of action with technical information found the fault quickly and accurately. Always confirm the cause of the problem and don’t rely on what you have seen before as it may not always be the same.
Fig 3.
- 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!
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- Quality street
The MOT has gone through change over the past few years. There have been changes in the way the MOT tester and the MOT Centre Manager become eligible to operate a Vehicle Testing Station (VTS) through the qualifications that are available through various national and local training organisations, through to the MOT tester having to manage their own Annual Training and the Annual Assessment.
In combination with the revised MOT Inspection Manual (aligning to the European Directive) being implemented during May 2018, some confusion may exist in this ever changing sector.
The VTS has several people roles that exist, one major role; the Authorised Examiner (AE) or Authorised Examiner Designated Manager (AEDM) being the person having the ultimate responsibility within the business.
A new VTS and those changing their approved status will need an AE/AEDM to hold the Level 3 Award in MOT Test Centre Management prior to the VTS becoming approved by DVSA. Most training providers will deliver the MOT Centre Manager qualification. Part of the qualification is that the person understands how to operate a Quality Management System (QMS) for the purposes of the VTS. This has been identified as an area that most people struggle with within the qualification.
To implement an effective QMS program, the business must initially internally agree the standards that they set. The results are then collected and reported into the QMS. Any problem should have a corrective action. This should be written with an indication the people responsible to carry out the action along with a completion date. If the same problem repeats, then a plan should be developed to improve the situation, and put into action.
The following highlights a few areas that where the QMS needs to focus.
Training
The AE should ensure all staff (employees and contractors) fully understand their responsibilities. This enables them to carry out their job accurately and remain compliant with the necessary requirements.
The MOT tester should ensure that they meet the requirements of the MOT tester Annual Training and Annual Assessment. This year the annual training includes updating their knowledge of the MOT Inspection Manual which was introduced in May 2018. Most MOT testers will be familiar with the revisions and updates to the MOT Inspection Manual, either through specific training prior to the changes or reviewing the Inspection Manual during its implementation stages.
The AE should also ensure that the MOT testers that carry out tests at the VTS, are compliant with the requirements. Failure to do so will result in the MOT tester unable to test vehicles. It should be noted that some MOT testers that have not met the requirements have taken many weeks to become reinstated as an MOT tester as a result of non compliance which could reduce business income.
At present there is no requirement for the MOT Centre Manager to comply with the updating of their MOT knowledge but this could change in the near future.
Procedures
The AE should ensure that everyone involved in the MOT testing process within their business has access to key information, especially focusing on MOT test logs and MOT Test Quality Information (TQI).
TQI can be accessed by both the AE and also the MOT tester, reviewing the MOT test data applicable to their role. The data can indicate both strengths and weaknesses with the MOT testers and the VTS, it is therefore important that this data is regularly reviewed to identify any anomalies within the data and implement an ‘action plan’ to correct any deficiencies, therefore both the MOT tester and the AE have a responsibility in this area.
MOT TQI was highlighted as a requirement for the MOT tester annual training/annual assessment. It is therefore suggested that the MOT Centre Manager also updates their knowledge on Test Quality Information (TQI) and also MOT test logs.
The AE should ensure that the relevant people know procedures for the reporting of equipment defects/problems, the equipment maintenance and any equipment calibration requirements within the specified dates as indicated by the MOT Testing Guide. The AE must ensure that any appropriate records (calibration certificates) are kept and the records are held securely.
The AE should always ensure that the equipment is maintained and calibrated correctly, if a problem is detected (yes things do go wrong) preferable before a breakdown occurs then a clear process should be identified and the rectification of the equipment recorded.
Assurance
The MOT tests which are carried out at the VTS must always have the correct result, the security of data, information and passwords are maintained which will lead to the reduction in risk of MOT fraudulent activity. The protection of data used in the MOT process needs to comply with the General Data Protection Regulation (GDPR) which was also introduced in May 2018 replacing the Data Protect Action (DPA) that previously covered the data. The AE has a duty to ensure this has been complied with.
The process should also include a Quality Control process of the MOT tester to ensure that they produce satisfactory results, and to identify any future weaknesses in their MOT test procedures.
The MOT Testing Guide (updated earlier this year) indicates that a QC check needs to be performed on an MOT tester every two months. Best practice would indicate that the QC process is completed on each MOT tester more frequently such as every month. The QC check should be recorded and kept in-line with the requirements. The QC report should indicate the strengths and weaknesses of each individual (not just indicating the MOT tester is OK) with an ‘action plan’ (further training etc) on how to reduce the weaknesses. The next month Quality Control report should then indicate how the MOT tester has performed against the ‘action plan’. This could help to reduce the VTS risk score, improving MOT tester performance but also increase business performance.
Performing and recording quality control checks within an MOT business can be time consuming and often gets forgotten. The person carrying out the MOT QC must be carried out by an approved DVSA MOT tester. The QC can be achieved within the MOT testing team providing more than one MOT tester is engaged (one MOT Tester is nominated as the QC) or alternatively a service that an outside agency could provide. A Vehicle Testing Station with only one MOT tester could have a reciprocal arrangement with a nearby similar business by carrying out the QC check on each other.
Improvement
An effective QMS used within the VTS should identify any weaknesses that could put the station at risk. Once a weakness has been identified the business should develop an action plan to improve within the area of weakness. This will typically lead to an improvement.
All these points will help to achieve a low VTS risk score. The MOT centre manager should read and understand the various documents provided free by the DVSA on how to carry out a VTS risk assessment and to hopefully reduce the VTS risk score.
The AE can find out more on the qualification by contacting a recognised training provider delivering the MOT Centre Manager Qualification, this will help them better understand the requirements of a Vehicle Testing Station and the various MOT Testing documents and standards associated with MOT testing. Many of these requirements have been revised over the last few years, and it is a requirement for the AE to constantly update their knowledge to remain current. Remember the MOT Testing Guide was revised in early 2018 and many AEs do not have knowledge of the new requirements.
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