A BMW 320d arrived into the workshop with a complaint of the headlight leveling system not working.
Where I worked at the time this system was a roadworthiness test fail and the owner had been quoted around $2000 for headlamp unit replacement.
I was tasked with checking this out as a second opinion. The owner really didn’t want to spend this kind of money if it wasn’t necessary.
The diagnostic process
Firstly I want to read fault codes. There’s quite a lot to consider here, ride height sensors, headlight servo motors and connections to name a few. Also a high probability is water ingress in these cars. The scan shows a no communication fault for both headlight motor units. My first check is going to be powers and grounds. At this point I’m thinking the likelihood of two headlamp units being faulty is slim.
After reading a wiring diagram and identifying my power and ground I proceed to check and straightaway see no power at either headlamp unit motor. The grounds are present. Checking the outputs from the control unit shows the powers are working from this side.
I’ve now established that there’s a break in the circuit. Using a fused jump wire from the control unit to the headlamp I prove my theory. Everything works as it should and I can clear those fault codes.
Finding the cause
Is this likely to be a broken wire or are there connector blocks on this loom where the connectors have come loose?
I usually start from outside the vehicle where wiring and connectors are more likely to be exposed. In my experience if there has been some body panel repair work that’s a good place to start. And that was the case for this vehicle. It had extensive work carried out on the right hand front fender at some stage.
The wiring loom had been routed incorrectly and it was chafing against a sharp edge that hadn’t been repaired correctly. Stripping back the loom I could see the damaged wire. .
It didn’t take much effort to pull it apart, only the insulation was holding it in place. Other wires in this loom were damaged too and it was only a matter of time before they too would cause more issues.
To prove my theory here I moved up the loom and connected my multimeter. I turned on the lights and could see I was getting power to that point.
Fixing and Conclusion
Once I repair this wire I’m confident this issue will be fixed. This diagnosis and fix is far cheaper than the quote for two headlight unit replacements.
Replacing components without proving the fault first is expensive guesswork.
These are most likely a non return item, so you’re stuck with them. That means you now need to repair the actual issue and then charge the customer for parts that were not required.
I wish this was an isolated case but it isn’t. This is common in my workshop, time and time again I seem to be the guy who gets the vehicle for either a second opinion or I’m the third or fourth workshop to look at it. And most of the time it plays out just like this.
This vehicle went on to pass its roadworthiness test and the customer was happy to pay a lot less for the repair.
I got the #icon magnetic mat from #harborfreight. I don’t know why, I didn’t even want it. Peer pressure perhaps. I couldn’t turn on YouTube without seeing this fecking thing every second or third video. What am I even going to do with it? I have flat surfaces, I’m not running around the workshop at such high speeds that I’m afraid my tools are going to fling themselves at cars. I’ve worked for years on cars and have maybe left 2 tools in an engine bay that whole time. So what use is it? I got the second last one in my store this morning. People were rushing in to get it. It’s a cloth with magnets in it people! Anyway, I got it, half price, today only ONE per customer, you know in case you needed more to stick all over the cars your working on, heaven forbid you might just use your trolley or tool cart. It’ll be here all day with these heavy items on it, let’s see if a magnet can hold up metal things! If you feel aggrieved that you didn’t get yours, this one may be for sale, at original — what I paid for it plus P&P — price, if it pisses me off enough and starts collecting swarf and other scratchy materials — as I suspect it will.
This 2005 Mercedes-Benz with 83k miles arrived on a flatbed with an intermittent crank no-start complaint. According to the owner this has happened before and he’s had it looked at, but he has no documentation showing what the issues were at that time or what work was done then to get it running. Of course, I can’t assume it’s the same problem as before anyway — so I start by looking for the issue as if this is the first time it’s happened.
Finding the issue ❓
When I got the car off the back of the tow truck it started right up. But it struggled to run above 1,000 rpm. A code scan showed no fault codes whatsoever, but in live data I could see the O2 sensor remained lean of WOT. Straight away I’m suspecting low fuel pressure. So I turned the vehicle off to connect my fuel pressure gauge, but when I went to restart it to see my pressure readings, it turned over fine but wouldn’t fire up.
As suspected — I have no fuel pressure.
Next I checked powers and grounds to my fuel pump. Luckily these vehicles are easy to get to the wiring in the luggage compartment, I added a substitute load and my multimeter back there and turned the engine over. I have full power, ruling out a wiring issue. I’m sure at this stage that I have a faulty fuel pump.
In conclusion
With the data collected it’s fair to say the fuel pump is at fault. Nothing fancy, just a clear and concise diagnosis. I don’t know what the earlier issues were as the owner didn’t know anything except it stopped and when he got it back it was running again. It did have a lot of new parts fitted, like plugs, coils, a MAF sensor, and possibly some cam solenoids. There’s no evidence these were fitted without being needed, but I have my suspicions.
Chances are it needed all those parts or was going to soon. It is a 2005 car after all. For now the owner is happy to have it back for some trouble-free driving. Oh, and we got his roof working again too, so he may even get a chance to get some sun!
I decided I’d use the NotebookLM to create a diagnostic test plan for a problem car I’ve been working on.
While doing research and adding information to the notebook I noticed a wiring diagram I looked up had an EGR valve listed, I knew this particular car didn’t have an EGR valve so I queried Google AI — just trying to use this AI to its full potential — and it confirmed that this particular engine code did have an EGR. I insisted that it didn’t.
I ended up have a full on fight with this AI as it insisted it was correct and I was wrong. I eventually told it to check VW’s SSP on this engine which I gave it a link to and finally it agreed and even apologized to me.
How ridiculous is this? I was fighting with an AI that has a barstool expert vibe going on.
I went to the Gemini app — which for some reason is not connected to the home page Gemini — and told it the story of what had happened. It’s response was,
What you ran into is one of the most annoying traits built into LLMs: sycophantic doubling-down.
When an AI model makes an initial incorrect assumption, its transformer architecture treats its own previous generated text as ground truth for the rest of the conversation. Instead of re-evaluating the physical reality of the machine, it starts doubling down—inventing plausible-sounding nonsense just to make its first answer seem logically consistent. It prioritizes sounding authoritative and coherent over actually being right.
It takes an explicit override—like referencing the factory Self-Study Program or physically pointing out what’s under the bonnet — to force the model to break out of that loop, drop the ego, and admit it was hallucinating.
This is absolute proof that AI is just going to act like a human, when it’s wrong it just throws the other guy under the bus.
An update on using AI — specifically NotebookLM — as a diagnostic companion tool. I’ve been putting it through its paces for over a week now, and the results have been a mixed bag.
The Good
There are certainly plenty of upsides to this system. You can upload or link documents, videos, and even photos or screenshots for the AI to analyze and reference in its responses.
While there is a limit on the number of sources you can attach to a single notebook, I found a neat workaround, using Google Docs via Google Drive. PDF uploads can quickly eat up your available source slots. However, if you create a single Google Doc, you can paste extensive technical data into it, and NotebookLM counts it as just one source. For example, I pasted the contents of four separate PDFs into a single Google Doc, saving three source slots in the process.
Another trick that worked remarkably well was scanning pages from technical textbooks and uploading them as PDFs. In every case so far, the AI was able to OCR and read the scanned pages without missing a beat — which is pretty impressive.
The Not So Good
Most of the downsides come down to minor quirks, though I did encounter a couple of server-side slowdowns and outages. When you’re trying to build a reliable tool for real-world shop work, server downtime gets frustrating very quickly.
The issue with textbook scans was double-edged. Right after uploading a batch of scanned pages, the notebook began to struggle with answering queries. It was hard to tell whether the complex scanned document caused the hiccup or if it just coincided with a background server lag event (the kind where everything seems fine until you push the issue and find out there’s a “known micro-outage”). Either way, it interrupted the workflow.
During that time, I read that NotebookLM can occasionally get confused or output odd results if your source documents are exceptionally long or highly technical — especially when packed together. That said, I only had 23 sources active, and the material wasn’t extraordinarily complex.
Another frustration is the Audio Overview feature. Generating a podcast roundup of your technical data sounds great on paper, but the output featured two generic hosts engaging in overly casual, energetic banter using my diagnostic notes. It might work well for general topics, but for technical diagnostic material, it felt completely out of place. I suspect tweaking the prompt parameters could steer the tone toward something more professional, which I’ll test out down the road.
Lastly — at least for this first week — is response latency. At times, the system can take a surprisingly long time to process sources and collate an answer, even for relatively simple queries.
Conclusion
Despite the quirks, I still think this setup has huge potential. Running past diagnostic job notes showed that when it works, it gathers relevant data and formats it into clear actionable reports.
The biggest learning curve is prompt structure. Learning how to ask the question is key. Keep it factual, supply the essential variables, and avoid fluff — just the facts, ma’am. When fed a clear prompt, it can deliver solid output.
It’s still very much a work in progress, but worth continuing to refine.
No, it’s not about AI doing your job or stealing your livelihood. For once, it could be a good news story about an AI assistant actually helping you to get organized.
Well, at least that’s the sales pitch. I’m trying to prove the concept, and so far it’s going well. But will it keep up the pace under pressure? Only time will tell.
How is it helping?
I’m a relatively new user of AI assistants, and I went into the world of AI as a skeptic. Which is my default mode: Question everything — believe nothing — until it proves itself in front of your eyes and can be explained.
We’re led to believe that AI can do everything! I’m of the belief it can’t do anything unless it’s told to do something. Kind of like a dog: you feed it with information, and then it performs tricks based on that.
If you ask it a question, it’s not sitting there honing its inner thoughts. It’s scraping the web and its large, human-fed database for answers that match your query — all dressed up in smart language to make it seem like a conversation.
I’m not trying to run it down; I happen to think it’s cool, and it’s grown on me. It can be a fast way to find and collate simple information. But the problem is this information isn’t guaranteed to be accurate. It’s the world wide web, after all, which is littered with misinformation.
The standard NotebookLM 3-panel workspace: Sources on the left, grounded AI chat in the middle, and notes/studio tools on the right.
So, how do we make this a useful tool?
My AI assistant of choice is Gemini. The main reason for this was ease of use: it’s tied to my Google account, so Google Drive and my other apps work natively with it. That’s how they get you, I guess!
Alongside standard Gemini, there is Gemini Notebooks (also known as NotebookLM). This is where we can store accurate information in the form of notes, TSBs from PDFs, web links, or live Google Docs directly from Google Drive.
Basically, here is how it works: we create a notebook — let’s call it Diag Notes. In that notebook, we attach notes, links, or videos related to that specific topic. Because this is information you collected yourself, you know you can trust it. Now, when you search for a diagnostic fault or technical spec, it returns answers based only on your verified data. No more reading a load of half-baked forum posts or speculation when all you need is correct factory data.
Some restrictions to keep in mind
There are, of course, a few limits to keep in mind. Depending on your plan, each notebook has a source limit (often up to 100 sources), which includes document uploads, web links, and drive files. There are also per-file size ceilings on heavy PDFs, though you can easily work around them.
So if — like me — you were thinking of just uploading every single note and file you have into one giant catch-all notebook, beware: it doesn’t work well that way.
Honestly, sitting down and dividing your notes into concentrated areas pays off in the long run. Ask me how I know! Having one notebook dedicated to EGR systems and another dedicated to ABS braking proves much more focused and leaves plenty of room to add new files or TSB’s as they inevitably become available.
A quick tip if you’re getting started: Plan your notebook topics before uploading everything. Because you can’t easily drag and drop files between notebooks once uploaded, taking five minutes to set up dedicated containers (e.g., Braking Systems, Fuel Systems, Electrical TSBs) saves you from having to re-upload files later.
Watch out for heavy, image-laden TSB PDFs. If you hit a file-size wall with a graphic-heavy bulletin, don’t throw it out. Copying the text into a plain .txt document or a Google Doc gives you 100% of the factory diagnostic logic, specs, and DTC descriptions in a file that’s a fraction of the original size.
Why the Google Sync Wins
If you’ve ever dealt with heavy factory service PDFs, you know they can be absolute file-size hogs, loaded down with full-resolution graphics, uncompressed schematics, and rendering bloat. Try uploading a stack of those, and you’ll hit a wall pretty quickly.
Here is the workaround I stumbled onto that completely changed my setup: Google Docs.
Instead of wrestling with a 200MB PDF, I copy the text into a Google Doc and use a screenshot tool to grab the relevant scope waveforms, wiring schematics, or pinout tables. Now, that massive PDF turns into a clean, lightweight 2MB Google Doc that uploads in seconds.
But here’s the real kicker, and the reason staying inside the Google ecosystem makes sense here: when you link a Google Doc to a notebook, it becomes a live source file.
Six months from now, when you encounter a weird issue or failure on that same system or come across a fresh TSB, you don’t need to create a new file or burn through upload limits. You just paste the new info into your existing Google Doc, open NotebookLM, and hit Refresh Source. Or just refresh the page, I did notice that the Refresh Source option didn’t always pop up.
The AI updates its knowledge base instantly. No managing twenty different file versions, no creating extra accounts, and no clutter — just one focused document that grows alongside your real-world shop experience.
What does the future hold?
At this point, I’ve only scratched the surface. I’ve used it in the workshop, but I’m still adding information and getting familiar with how it behaves under real pressure. So far in testing, it has performed admirably, and I can’t wait to put it to work on a real stinker of a diagnostic job.
In a previous post, I talked about keeping notes while diagnosing vehicles and wondered if there was anything better than a pen and paper notebook. While I still love that traditional approach, NotebookLM feels like a natural extension of it.
I don’t intend to give up paper notes anytime soon — NotebookLM will simply be a companion to them. I’ll add my handwritten notes right into the notebook as a source, either by photo or PDF via Google Drive.
I bought this LS2000 on marketplace, it wasn’t expensive and my thought was it would be a handy scope to have out on the road for quick checks.
This is where I would normally use my Vantage Pro alongside a multimeter. But this being Sun from the 90’s I thought it would be like having a second Vantage. It isn’t.
That’s not to say it’s bad, it’s an older scope, and it feels it. But I still like it. It’s just different.
To find out if it can become a tool that’s useful and I can trust I’m going to do a number of tests with it up against other tools I know well and see if it will be added to my arsenal or destined to sit in a drawer.
I’ll probably try my hand at a video and upload it to YouTube soon.
I went to a place called The Bomb Shelter in Akron today and it stirred up some great memories.
There was a Citroën DS outside which piqued my interest straight away, a Citroën in the USA is a rare sight but an immaculate DS in North eastern Ohio is rare indeed.
Inside the main door there’s a 1990 Yugo which although rare not surprising — there’s a great story behind Yugo in America that’s well worth a read or watch — but entering the back area there is a fantastic line up of rare euro cars including a Citroën 2CV Charleston, a Citroën Ami, a DeLorean DMC-12 — best known as the Back to the future car — and a Citroën CX Pallas series 1. All in absolutely mint condition.
It reminded me of my own long-forgotten ownership of a CX in the late 90’s. It was a great story of how I came to get it and what eventually happened to it. It sat in a yard for quite a while and I really had to convince the guy to sell it to me. As far as I remember it was the product of a long running insurance claim.
The story goes…
A captain from a ship that sailed from Rosslare to Fishguard owned this car, the parking brake was notorious on these cars and when it was worn it had what we called the rocket launcher handbrake because when it was worn it would pull up almost vertical before it would engage.
Anyway when the captain came back after his shift he found his car had rolled down the carpark and hit a wall, being blamed on that notorious handbrake, breaking the front bumper cover beyond repair and badly damaging the bonnet and radiator panel as well as the radiator.
I eventually bought it as a damaged repairable. I could not find a bumper anywhere, I fixed the bonnet and panel and had it painted and I replaced the radiator.
It took almost a year to get a genuine bumper cover from France at a horrific price of almost £600 (Irish punts in ’93 or ’94). When I finally got it altogether my Dad — who wasn’t into cars at all — fell in love with the car, not surprising, the smell of the leather interior alone would sell this car.
Anyway when he retired in ’98 or so he didn’t want to pay the large road tax anymore so I bought it back off him.
I kept it for a couple of years and only sold it when my son was a baby — for money frankly, he was quite sick for the first 18 months or so of his life.
I sold it to an enthusiast who slowly and surprisingly, ruined it until all it was fit for was the scrapyard. I was quite annoyed as I really didn’t want to sell it to him but he literally begged me. At the time I had two running Citroen 16v Gti BX’s I was willing to sell one of them instead so I had an out.
One of my 16v’s was the one I rushed my wife at the time to hospital because of complications with my sons birth so I was never going to sell that. Unfortunately that car was written off when someone crashed into it when it was parked, a drunk driver with no insurance.
Anyway, my rambling comes from memories of seeing Citroën’s today.
Citroën, Alfa Romeo, VW, Audi and Mercedes have always been a big part of my life and have plotted my journey of where I was in my career at points in time.
If you want to see some really nice French classics in pristine condition it’s well worth a visit. There was a slide in camper and some motorcycles there too but I didn’t get to investigate them. Yet.
