A month in the life of a vehicle technician
Failure is always predictable according to Frank, so you need to learn to expect the unexpected
Published: 30 May, 2023
The last topic concluded with a promise to share my experiences working within a workshop lacking in essential infrastructure. I hope by explaining my failings and limited success, it helps identify the importance of correct process, correct tools and comprehensive systems information. If you forgo one or more of these three critical elements, failure is predictable even before you begin a repair task.
The most basic and simple error; Failing to assess the battery rating and cell condition. Note I didn’t focus simply on voltage. The first example was a Ford Focus 1.6 ecoboost, suffering windscreen wiper failure. The car was driven to us, and the customer explained the battery had gone flat and been charged.
Conductance test
I began with a conductance test with my personal Midtronics MDX 600. Voltage was 12.47, rated 540 amps, however it only returned 346 amps. Please refer to Fig.1. I ordered a replacement and decided to continue testing the screen wiper problem. The vehicle started and drove into the workshop, so I began checking voltage and ground at the twin wiper motors. There was no change of state, however the voltage was below 9 volts after only a very short time. So, I fitted a temporary good battery and continued with my tests, only to find the wipers working normally.
The explanation is straightforward; CAN and lower priority networks often hibernate with system voltage drop. So, my knowledge, process and tools won the day here. The next problem, another Ford Focus, had much more challenging issues. Initially it drove to us with starting problems, then failed to start.
Global vehicle check
I began with a global vehicle check using the garage TOPDON serial tool. It had reasonable systems access and displayed steering column communication loss with the body control module; B1026:87-2F. It showed two keys stored, and the immobiliser was registered in the PCM. We had limited wiring access via E3 tech data, but crucially no test plan data. We were dead in the water now, relying on the common-sense method. We decided to ramp the vehicle and examine wiring and PCM, located we thought under the front wheel arch.
The PCM housing was damaged, probably from a light frontal impact, and had allowed water ingress. The next series of events taken over several weeks is a textbook example of how to fail in a repair and diagnostic process. My only satisfaction was that the decisions were not of my making.
The cost of a new PCM with programming and coding exceeded £1,500. The owner could not afford the repair, so a second-hand PCM was suggested. Mistake number one; Cost must never influence correct process.
A unit was sourced by the owner in Poland. Mistake number two: Never allow customer interference in the repair or part procurement process. The owner was instructed to send the original PCM to Poland so programming and coding could be transferred across. Mistake number three: Never use or trust third party contractors unless personally known to you. Although this is technically possible, and we at ADS have done this many times, you have now lost control of the repair. This mistake is fatal and has no comeback.
The PCM was fitted to the vehicle and guess what? No change in the symptoms. I was then re-tasked to check the fault from the sketchy wiring schematics. I had no enthusiasm left at this point, so let’s score it as mistake number four; You need to have a positive mental attitude. My evening’s Vodka consumption didn’t help. Having exhausted all limited direction of diagnostic enquiries, it was time to put the train back on the tracks.
Please refer to Fig.2.
I consulted a local friend and expert, Paul Emmett from Reedley Service Centre. This was correct decision number one. He owns the Ford IDS platform, with which one can programme and code the PCM. Following this process, the keys operated the central locking, and the instrument cluster became active. Despite this apparent progress, there was still no cranking. As part of the coding process though, a global scan was conducted, resulting in a curious and previously unknown error. It turned out that both rear wheel speed sensors were defective. Paul suggested replacing them before continuing; Correct decision number two. The sensors were replaced, and the vehicle started normally with all stored codes cleared. I place this explanation in the same column as my previous observations. In short, wheel speed sensor errors are broadcast on high speed CAN, therefore the error frames must have corrupted the network, thus preventing crank start.
The failure to understand this I put down to incomplete serial data from TOPDON.
I am sure I don’t need to recap events, and I am not going to expose the decision makers, but as the technician in question I should have refused to continue. This was mistake number five. I don’t know what the owner was charged for the repair, but I hope it was more than the original estimate.
Challenges
Let’s end on a little restored personal pride; A Ford Transit Connect with a faulty power steering assist system was presented, with a blown 60amp control fuse for good measure. Challenge number one; Ford would only supply a complete vehicle wiring harness for £600 despite the auxiliary fuse panel being easily replaceable. Please refer to Fig.3. I decided to replace the fixed fuse assembly with the correctly rated value and conduct current flow analysis by logging serial data and directly using my personal fluke clamp. Current peaked at 65amp for a few milliseconds. Average current flow was 35amps. Please refer to Fig.4.
I was made aware of known issues with steering rack faults, and I am waiting to see if the fault reoccurs, which will mean a new rack assembly is required. This customer has no issues with cost.
I have archived many examples of good and challenging decisions facing technicians with limited access to essential assets. More next issue.
- Process not problem
Frank’s ongoing look at the recalcitrant VW Golf R serves as an example of why process will win every time
- Non-intrusive diagnostic techniques
The last two topics in recent issues focused on combustion issues and the various tools, service and repair process available to us. Two reasons have directed me to develop this debate further, firstly an email from my much-respected friend Phil Ellison at ASNU, and a VW Golf edition 30 presented to our workshop with poor running at low and transient throttle position. I was also involved in a conversation with friends in Perth, Australia over valve timing issues.
I’m going to respond to Phil’s interesting input first and clarify something especially important to all diagnostic techs. All decisions we make must be evidence based and not opinion. This is an extremely broad statement, but simplifies the fact that if you do not have access to the required tools, software, or process skillsets your decisions will be opinion-based!
I can relate this to my time building military aircraft, where nothing ever happens as a result of opinion. You could quite literally switch off and simply follow the build schedule and submit your work to inspection. You were not paid to have an opinion. This is why I left!
I may have previously left an impression that it was not necessary to fully evaluate injectors in a test bench, if this was so, then I apologise as my thoughts are the exact opposite. My intention was to ensure that you fully explored all causes of incomplete combustion while the engine is running, as most engine work now carries a high labour content! Do not, however make the mistake of letting cost dictate your process. Phil did pick up on the common issues of injector removal damage where specialist tools are required. The use of fuel additives, which can be a common cause of internal injector damage especially to plastic filter baskets, where any debris is then deposited in the basket effecting fuel flow. Direct injection technology now demands the absolute best fuel quality, often reinforced by manufacturers placing fuelling advice inside the filler flap.
Phil also picked up on a common issue I did omit; Stop/Start. Hot engines with an increase in stop events, with fuel trapped in the injector often causes lacquering of the pintle. Heat in the combustion chamber dries any combustion residue and oil on the injector tip. I’m coming to the inlet valves very shortly…
Fuel trim or correction does not fix problems, it can exacerbate them, imbalance in injector delivery or as Phil pointed out deterioration of the spray pattern will cause bore wash, premature lubrication failure, and an increase in crankcase emissions, larger fuel droplets do not combust fully.
Interestingly, he pointed out that new injectors are produced with a +/- 5% tolerance.
Potentially misleading evidence
The Golf appeared in our workshop just a few days after I had finished my topic. I was not involved in most of the diagnostic process or repair but was in discussion over potentially misleading evidence.
The vehicle had covered 106,000 miles, and was suffering from poor idle and incomplete combustion, with a mil light indication.
Step 1/ serial interrogation
0568/P0238 boost sensor, signal high, frequency 1
0768/p0300 random/ multiple cyl misfire, frequency2, counter re-set 255
0772/p0304 cyl #4 misfire intermittent frequency2 counter re-set 255
The next step taken was a cranking current differential test, showing no apparent mechanical imbalance? Back to this later.
Coil and plug failure is a common problem and is an obvious job for the Pico scope, no problems with burn times or primary current saturation here.
David Gore, our diagnostic tech, opted for the first look sensor in the exhaust next. I’m not sure if he opted for WPS in cylinder or not. This would have been my preferred choice, but as the saying goes too many chefs…
If you refer to Fig.1, The image is triggered from ignition, sequentially 1342 from left to right. I’m going to let you debate this image, as I intend to cover this in detail next month. I bow to Brendon Stickler’s wisdom on exhaust pressure evaluation. My debate is focused on the properties of pneumatic pulse delay from the cylinder head to tail pipe. I have since proven this and will discuss this in the October issue.
The next and obvious decision was to remove the manifold and check the intake tract and valves for carbon.
So, as you can see in Fig.2, there is excessive intake valve carbon. This is due to several factors, the most common of which is no self-cleaning from the fresh fuel air intake cycle. Other factors include, lengthy oil service intervals, not replacing oil separation filters, poor fuel quality, driving environment, poor or incomplete combustion cycles, incorrect atomisation and air swirl during the intake and combustion preparation cycles. Remember, direct injection can separate the fuelling into several events on both the intake and compression strokes.
Value
Back to a comment I left open earlier, I hope you are still interested? The value of compression is determined by the mechanical engine efficiency and volumetric efficiency, Pumping losses! So why didn’t a problem show up during the cranking balance check? As this test is based on compressional resistance. Accepting that when the engine was at idle it ran badly and would eventually disengage the injector cycle in cly #4? the answer is rotation speed increase reduces the available time to draw in fresh air. If you compare nominal compression values say 10-12bar against the value at idle they will only be around 3.5 bar!
The detrimental effects of intake fouling only tends to occur at closed and partially open throttle, where the pumping losses are the greatest. The dtc relating to boost pressure sensor value high, can be caused by ignition misfire or unstable intake pulses.
Finally, the injectors were subject to the Spanish Inquisition in the ASNU bench. The results (see Fig.3) confirm substantial fuelling imbalance causally relating to my previous comments.
My grateful thanks to Phil, David (and myself), for the technical input in this topic. I’m off to the workshop to check the delay characteristics with WPS in cylinder and FIRST LOOK sensor in the exhaust.
- New tech support from Repairify
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Two new Business Development Manager have been appointed at Maverick Diagnostics.
Matt Oddie, formerly of Opus IVS, and Glenn Hopkins, who joins from GSF Car Parts, will cover the north and south respectively.
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OE tools are needed for EVs. As of April 2023, there were over 760,000 fully electric cars on the UK’s roads. When an EV needs to visit a bodyshop following collision damage, it is required that the work is carried out at a workshop that is EV-ready to ensure it is repaired safely and to the highest possible standards.
Becoming EV ready requires ongoing investment by the business in refresher courses to ensure their technicians, whether apprentices or experienced operators, have the necessary skills and knowledge to work on the vehicles. However, there is something even more important than the training that is required and that is the tools that perform the work.
Tools are the lifeblood of any good workshop, but they are especially important when working on EVs, which have to be serviced differently from their petrol and diesel counterparts. EVs must be shut down before they can be worked on, which is where OE tools are critical. The proper and correct processes to shutdown EVs are very well documented on OE tools whereas they are not recorded for aftermarket tools. In addition to this, it is important that technicians regularly undergo training to ensure they are up to date with the latest tools and updates.
asTech tools have been designed to support repairers by managing the hardware and access to the OE tools they are using to work on EVs. This means that customers have peace of mind in knowing they have a remote solution that allows them to work safely on EVs and can easily diagnose, program, and calibrate the vehicle.
