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The Technician’s Log: Complex Diagnostics Protocols Decoded, Part I

Welcome back to the Technician’s Log. Today, we are going to dive into the world of diagnostics. Because as every aspect of a commercial motor vehicle becomes more complex, diagnosing issues becomes ever more challenging for diesel mechanics. Whether you are dealing with electrical issues or unknown vibrations, you never know what problem is going to present itself when the rig arrives in the repair bay.

You may think you have seen it all, but chances are you haven’t. As technology changes things up, it will become harder to keep up. And this is especially true when it comes to diagnostics. Not only might you need entirely new diagnostic tools, but you will also need new sources of information. If you don’t want to go back to basics to have all your bases covered, then you need to keep an open mind. Join us for Part I of this important two-part series.

What Are the Top Diagnostics Issues?

A recent survey asking diesel technicians what diagnostics problems, wishes, tips, and tricks showed some interesting results. The answers cover a wide range of diagnostic challenges technicians face on a daily basis.

The top issue identified included:

  • Diagnostic complexity keeps growing.
  • The wrong conclusion gets made.
  • Accurate diagnostics are hard to come by.
  • It is difficult to duplicate the problem.
  • Transmission failure is becoming more complex.
  • Noise and vibration issues are challenging to diagnose.
  • Finding out what failed is easy, figuring out why is harder.
  • Intermittent electrical issues are vexing to diagnose and fix.
  • Engine diagnostics are constantly changing.

These are common issues that diesel technicians face, no matter the size or operational type of their business. So, why not address each one in kind? Diagnostics doesn’t need to be a vexing problem. And we can help you figure it out.

Addressing Diagnostics Complexity

Big rigs are more complex than they have ever been. Where mechanics were once able to adapt to changes in truck technology over the span of their career, they now face technological leaps in short timeframes. Yet, in other ways, advanced technology has made life easier for technicians. Engine servicing, for example, has become easier thanks to advances in diagnostics technology.

Truck Repair Diagnostics

Here is one example. When was the last time a diesel technician has had to adjust the connecting rod shims for rods with poured babbit bearings? Another one you probably rarely see anymore is the need to replace ignition distributor points or adjust a dwell. These are just a couple of examples of techniques and procedures that are no longer required thanks to mechanical advances.

Today, engines need to meet always-evolving emission requirements. At the same time, they must meet increasing power output efficiency requirements. Due to these requirements, technologies that provide and facilitate efficient engine diagnostics are better than ever before. Today, modern engines have upwards of 1,000 or more diagnostic alert codes.

Addressing the Changes in Diagnostic Testing

Today’s repair information contains a massive amount of data. This data covers everything from specifications to test procedures, component locations and operations, wiring diagrams, lubricant specifications, tool usage, and so much more. To make sense of the data, technicians need to be able to properly identify and prioritize the information provided.

Of course, the technician could also make a best guess without the data, but the likelihood of a misdiagnosis goes up. To avoid this, trucking companies must take the time and set aside the resources to invest in a diagnostic testing device.

Still, a proper diagnosis does not end with reading an error code. Long gone are the days when a dozen or so pages in a manual will cover a specific engine type for the next decade. Today, the printed diagnostic service information for a decade out on a single engine could act as a doorstop. Add in the service information for all the vehicles in your fleet and you could build a library out of it.

That’s why going digital with your diagnostics information is key. Having access to all your service and diagnostics information for everything from fault descriptions to testing, connectors, and diagrams makes diagnosis and repair faster and more efficient. And you can do all this without getting your hands greasy handling a four-inch-thick diagnostic manual!

Never Assume a Diagnostics Outcome

If your technicians manage a static set of vehicles, they can expect to see the same fault codes all the time. Why? Because there are a limited set of fault codes out there. So technicians should be able to quickly gain understanding about the frequency of certain problems. But there are downsides to being so proficient at discovering common problems.

When you are over-familiar with a problem, you may presume a fix before thoroughly researching the problem. Don’t rely on a consistent set of circumstances to lull you into a sense of complacency. Diagnostic procedures can take a lot of time and effort as your technician works through each step. You must take a systematic approach to solving the problem.

Another problem that can arise from being quick to assume you know an answer is that you might overlook the actual root of the problem. Let’s look at a possible scenario. When fault code X sets when you replace the sensor will correct the fault code setting. But approaching the repair this way may mean you miss the reason why the sensor failed in the first place. Perhaps wires are damaged or there is too much heat beating on the sensor.

Knowing failure patterns and using them to save time can provide a great head start on diagnosing a problem. Still, it is critically important to make sure you are not deciding solely based on past experience.

Key Steps to a Proper Diagnosis

Modern trucks are built with fault codes for nearly every conceivable situation. Because systems on trucks interact with each other, it is not uncommon to see multiple fault codes set for a common problem.

In many cases, diagnostic procedures will tell you whether there are any additional fault codes sharing circuitry or relying on another system to provide an accurate reading. The key is to address every diagnostic and repair procedure in a methodical and step-by-step fashion. Step-by-step diagnostics procedures may seem like a pain, but they will ensure you get the job done right the first time.

A Step-by-Step Electric and Engine Diagnosis Checklist

Consider the following checklist when setting up your step-by-step checklist:

  • 1 – Gather information about when and where the problem occurs. This is especially important if you are dealing with an intermittent issue.
  • 2 – Learn as much as possible about the system you are working on by thoroughly reviewing service manuals, fault code guidelines and other diagnostic procedures.
  • 3 – Review any system wiring diagrams for circuits in the system as well as any circuits that tie in through any shared power and ground connectors.
  • 4 – Make sure you note harness routings to check for movement and pinch points. Remember that splices folded into harnesses can be difficult to spot for the untrained eye.
  • 5 – Check for anomalous heat sources near improperly guarded circuits. Also check that missing or damaged water shields aren’t allowing moisture to creep into internal connections.
  • 6 – Don’t be afraid to systematically check a circuit. Check to make sure all circuits are inspected for an open, short to ground, short to power, or short to another circuit.

We get it. You probably read the above checklist and thought to yourself, “That’s way too much!” But when it comes to safety, performance, and compliance, you can never be too careful. Going through all this effort to identify a problem helps you build patience and promotes a methodological approach. Doesn’t it feel good to chase down and fix problems? Adopting a diagnostic approach like this will ensure you successfully do so far more often.

Addressing Problem Not Found Reports

No technician likes to see “could not duplicate” or “problem not found” on a shop work order. This can be especially vexing if we know that a problem exists. It’s even worse when you have a fault code blaring in your face. After all, technicians have better jobs to do than simply trying to recreate a problem.

Above all, there must be good communication between the operator and technician. Excellent communication between team member is a top trait of a successful trucking company. Even though setting a fault code turns on the service lamp and records the code in the control module, there is typically insight that can be gained by knowing additional operating conditions at the time the problem occurred.

Finally, compare the vehicle operation against a similar model or with a known good part. While this option may not always be available, it does serve as a solid way to determine where a problem exists without a lot of extra diagnostic time — or replacing parts that were not actually causing the fault.

Thanks for joining us in Part I in our two-part Technician’s Log series examining diagnostics, electrical and engine diagnostics, fault codes, and diagnostics best practices. Join us next week in Part II of our series where we look at transmission diagnosis, noise and vibration diagnostics, and intermittent problem diagnosis best practices.

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