Explaining the Diagnostic Process

October 12th, 2014

Airdrie Automotive Diagnostics

Written by Chris Dekker, former co-owner at Tools in Motion.


The other day, a customer called us to ask if we had “one of those computers that tells you what’s wrong with the cars”. I was tempted to make a goofy response like “Yes, and I have robots that fix them for me, too!”, but I knew what they meant. The customer was talking about a scan tool. And of course, we do have scan tools; four different ones, in fact.

Scan tools have been around for decades and became a very necessary tool in the 1980s as vehicles switched from carburetors to fuel injection, which of course meant they now had an on-board engine computer. Today’s vehicles have between 5 and 50 on-board computers; the scan tool is a device that lets a qualified technician communicate with these on-board computers in order to diagnose problems, test systems, and make software changes. Today’s scan tools – many of which aren’t actually “tools” anymore, but laptop-based programs – are pretty advanced. That being said, most customers don’t realize how little the scan tool actually contributes to an accurate diagnosis, and how quickly in the process the human brain must take over from the tool.

One of the more regular things that we use a scan tool for is to diagnose a warning light, such as a Check Engine or ABS light. Whenever a warning light comes on, this means that an on-board computer has detected some sort of problem, and stored a “trouble code” as a result.  In the case of the Check Engine light, these codes read something like P0302 or P0171. Any code starting with P0- is universal between most vehicles, so the scan tool will usually add a definition so they read P0302 – Cylinder #2 Misfire and P0171 – Fuel System Lean, Bank 1.  Retrieving these trouble codes from the vehicle is usually a quick process, and this is where two common customer misconceptions (and sometimes, sources of frustration) come from:

  1. Because the code retrieval process (which is only the start of the diagnosis, as we’ll get to in point #2) is so quick, customers sometimes feel ripped off when they are charged $100-150 for this service. This is partially our fault, as most shops will show the service as a one hour charge on the invoice. If the service doesn’t take this long, it’s only natural for customers to get upset. It’s very important for us to explain that we’re billing customers for a $120 charge vs one hour’s labour. This might be the same dollar amount, but we need to justify the charge for what it really is: in part, a way to earn back the purchase cost of the scan tools being used. In total, our four scan tools cost over $25,000 and require another $3500 in software updates every year.
  2. Many customers also don’t realize that retrieving a trouble code is only part of properly diagnosing an issue. This is partially because we as professionals haven’t done a good enough job educating consumers; parts stores that will “pull a code for free and then sell you a part” aren’t helping the situation. For example, what’s causing that P0302 – Cylinder #2 Misfire? Is is a spark plug? A plug wire? It could also be an ignition coil, a fuel injector, a wiring problem, a bad sensor, a vacuum leak – even a mechanical condition such as low compression on that cylinder, a sticking valve, or broken valve spring. This is where a properly trained technician – and a whole bunch more test equipment – are required to narrow in on the real problem.


Here are some of the steps a properly trained technician will take in order to diagnose most Check Engine lights, once the easy part (pulling the code) is complete:

  • Using the scan tool, monitoring the PIDs (or parameter IDs) for the affected module. These are hundreds of numbers that the scan tool spits out in real time, constantly updating them many times per second. These can be temperature readings, voltages, duty cycle (on/off time) numbers, resistance values and more; and they have confusing names like B1S2 Ho2S, VGT DUTY % and VREF, etc:
    Airdrie Auto Diagnostic Numbers

    Some basic engine PIDs being graphed

    None of these numbers really tell you anything by themselves; it takes a skilled technician to know which ones are relevant to the problem being experienced, and to understand the relationship between these numbers. (When number A increases, number B should increase at the same rate, while number C decreases at half that rate, etc.) Interpreting all of these numbers will help the technician understand what’s going on inside the engine, and narrow on on which part of the engine is having trouble.

  • The technician will likely also consult published service information from the vehicle’s manufacturer – which we subscribe to – in order to familiarize themselves with how certain systems work, what readings to expect, etc. It’s impossible to remember everything about every single vehicle on the road, which makes the tech’s ability to understand service information, diagrams and wiring schematics very important. These service information subscriptions aren’t cheap, either – but like the scan tools, are a very necessary part of a shop’s tools and equipment budget.
  • The tech will probably also check for Technical Service Bulletins (TSBs). These bulletins, released from the auto manufacturers to service facilities like ours, serve to alert us to common issues we should know about. They may also contain information on updated test procedures, updated fluid recommendations, new specialty tools that have been released for a given repair, revised/improved parts that are available to fix certain issues, and more. A quick check of the TSBs will help the technician ensure they aren’t missing any important information that they need to diagnose an issue accurately and carry out a proper repair that lasts as long as possible.

At this point, the technician has probably exhausted all of the information that the scan tool, and their computer, can give them. Finalizing the diagnosis will probably require some hands-on testing with a variety of other tools. Sticking with the P0302 – Cylinder #2 Misfire, the tech may use:

  • An ohmmeter and spark tester to check the spark plug wires and ignition coil.
  • A fuel pressure tester and injector pulser/balance tester, used together to test the fuel injector flow rates.
  • A multimeter, test light, noid light, oscilloscope or other tools to check for wiring issues associated with the sensors, ignition coils and fuel injectors.
  • A vacuum pump, vacuum gauge or smoke machine to rule out the possibility of vacuum leaks.
  • An exhaust backpressure gauge, or pressure transducer to check the engine’s air pumping action and rule out a restricted exhaust system.
  • A compression tester, cylinder leakage tester or borescope to check for internal, mechanical engine problems.

Depending on the situation, there may be more – or less –  tests and tools required, of course. We feel that all of the additional work that comes after “pulling the code” is part of the proper, complete diagnosis, and it’s included whenever you pay us to diagnose a warning light on your vehicle. We hope this insight into what we do every day will help our customers recognize the value in the diagnostic charges that they are billed for. After all, by the time we’re done, we should be able to tell you exactly what your vehicle needs without any guesswork. It’s what we’re known for, and our reputation depends on it!

Understanding Tire Sizes

May 9th, 2014

Written by Chris Dekker, former co-owner at Tools in Motion.


We get a lot of questions about tires, and tire sizing, which is no surprise because the sizing format that has become the industry standard couldn’t be more confusing. What do all those numbers on the sidewall of your tire mean? Let’s break it down:


Airdrie Tires


  • The section width is pretty straightforward. This is the width of the tire, in millimeters.
  • The aspect ratio is where things start to get confusing. This is the height of the tire sidewall (from rim to tread), but this is expressed as a percentage of the width. For example, this tire’s sidewall height is 75% of 185mm, which is a little under 140mm. Because the aspect ratio is a percentage, a 195/75R14 tire is actually wider and taller than say, a 185/75R14 tire.
  • The “R” construction method means this is a radial tire, as with almost every tire produced today.
  • The rim diameter is expressed in inches – yes, we’re mixing metric and imperial measurements here for some reason! This tells us what diameter of rim this tire will fit on.

These measurements all often all that is considered when most customers shop for tires, but there are two more very important numbers on the side of your tires that shouldn’t be overlooked:

  • The load rating tells us how much weight the tire can support at its maximum air pressure without failing. For obvious reasons, your tire’s load rating should meet or exceed what is required by your vehicle.
  • The speed rating of the tire is often misunderstood. In theory, this number tells us how fast a tire can be driven without failing, but even cheap “S” rated tires are rated for 180 kilometers per hour! The ratings continue to increase as you move towards the end of the alphabet.

So, why not just put “S” rated tires on every vehicle? You’re not going to drive that fast, right? In reality, the speed rating tells us a lot more about the construction and stiffness of the tire – how it brakes, corners and grips – even how much it heats up travelling down the road. It is absolutely essential that your tire speed rating meets the standard required by your vehicle in order for it to handle and perform the way the manufacturer intended.

Recently, Global News showed a story where they equipped two Mazda sedans with new tires; one with the recommended “V” rated tires, and one with cheaper “S” rated tires. Not only did the car with the right tires ride and handle better, it also stopped a whopping 23 feet sooner when both vehicles had to brake hard from 80 km/h. This could be the difference between life and death in some situations.


Airdrie Tire Shop


Most newer vehicles have a tire size placard, similar to the one above, which will show you what size (plus load and speed rating) of tires your vehicle requires. It will also show you the manufacturer’s recommended tire pressure. A quick note on this: Always set your tire pressures to the recommendation on this decal. The tire pressure shown on the sidewall is the theoretical “maximum pressure” of the tire, and may be way too high for your vehicle!

Be a Happy Camper: Checking your Trailer

April 13th, 2014

Written by Chris Dekker, former co-owner at Tools in Motion.


Airdrie Trailer MaintenanceWith the weather finally starting to look better, lots of people are starting to think about summer, and the summer adventures that lie ahead. For many Albertans, that means a family trip in an RV. Camping trailers are by far the most popular form of RVs, and (we feel) for good reason. They are much easier to maintain than a motor home; since they don’t come with a second engine, transmission, brake and suspension system that needs attention. Providing you have kept your tow vehicle in good shape throughout the winter, you can expect your whole set-up to be pretty reliable.

That being said, trailers do need some annual attention. Most of the trailer break-downs that we respond to involve the trailer tires. There are a couple things every trailer owner should check before going out:

  • The tire pressure,  even if the tires look OK. If they haven’t been checked since last season, they are low for sure. Low tire pressure reduces the tire’s ability to carry weight and causes it to heat up more as it rotates. Low pressure is the leading cause of tire blow-outs.
  • Carefully inspect the tires, including the sidewalls, for any cracking or signs of separation. Many trailer tires are a bias-ply construction, and prone to the tread section peeling off. Before this happens, you may notice cracking where the tread section meets the sidewall of the tire. Besides being inconvenient, this kind of tire failure can cause extensive damage to the side of your trailer. Since they usually don’t see regular use and have a chance to “bloom” (this is a natural moisturizing process that occurs when a tire rolls, and waxes are released) regularly, it’s not uncommon to replace trailer tires well before the tread is worn out!

Trailers should also receive an annual inspection of their brakes and wheel bearings. Wheel bearing failure is the second-most common trailer break-down that we see on a regular basis. Sometimes, a “spun” or failed bearing can result in having to replace the whole axle, which can be an expensive proposition. The wheel bearings should be serviced at least every second season, which involves cleaning them, packing them with new grease and adjusting them, plus replacing the wheel seals. At the same time, the trailer brakes can be inspected and adjusted. If you can’t remember the last time you’ve had your trailer’s wheel bearings serviced, it has been too long!

ABS Brakes Explained

March 2nd, 2014

We know ABS brake repairs!
















The perfect photo for a cold day, we just had to post it! These little guys do the best illustration I’ve ever seen of anti-lock brakes in action.

Introduced in the nineties, ABS (or anti-lock brake systems) are a great safety feature that allows you to retain steering control under hard braking. On a skidding car a wheel that is “locked”, or not turning cannot steer; the car will continue to slide in the same direction regardless of where the steering is pointed. ABS brake systems automatically pulse the brakes for you, allowing the wheels to turn a fraction of a rotation every pulse, so you can control your steering direction while pushing firmly on the brake pedal.

How Far We’ve Come!

March 2nd, 2014

New car safety features sure have come a long way. Bigger and heavier doesn’t always mean safer, as illustrated in this crash test between a 1959 Chevrolet Bel Air and a 2009 Chevrolet Malibu.