Have you ever asked a mechanic for advice only to get bombarded with follow-up questions? If so, what you experienced was the start of a methodical repair process known as "The Three C's." The three C's are as follows; Concern, Cause, and Correction.

Get a free quote

Each of these pillars is essential and cannot be rearranged or discarded. They are the core structure of the vehicle repair process and, if adhered to correctly, will ensure your car is fixed right the first time.


Being the customer, this is your concern, and nailing it down will help the mechanic immensely.

Step 1: Notice The Concern

Concerns are symptoms that you've experienced that are prompting the repair visit. Symptoms can originate from any of the human senses, including sight, sound, smell, or touch. Conversely, a concern is not what you think the problem could be nor a specific repair you are scheduling.

For example, if you hear a grinding noise when coming to a stop and suspect that the brake pads are worn out, your actual concern is the grinding sound.

Sounds easy enough, right?

Step 2: Observe The Concern

As it turns out, obtaining a customer's symptoms is a great starting point but is far from complete in a mechanic's mind. To fully understand how to reproduce the concern (which we will discuss later), the context of the symptom must be disclosed.

The easiest way to explain this would be by taking you back to your elementary school days.

Your birthday is just around the corner, so you decide to write up some invitation cards for your friends. Do you remember what we used to write? Who, What, Where, Why, When & How.

The answer to those questions completely satisfied our friends' parents, and the same is true for your mechanic!


  • …experienced the symptom? (If not self, the information is being relayed 2nd hand)


  • …type of symptom was experienced? (Abnormal sight, sound, odor, or feeling)
  • … kind of road and weather conditions were present? (Speed bumps, gravel, rain, snow)


  • …was the symptom originating? (Right-front, left-rear, steering wheel, brake pedal)
  • …was the vehicle when the symptom presented? (Highway, parking lot, stop-and-go traffic)


  • …is this a concern? (Annoying, seems unsafe, was told it was abnormal, online forum advice)


  • …in the day, did the symptom present? (Morning, afternoon, evening, night)
  • …operationally, does the symptom present? (Turning, accelerating, coasting, braking, idling)


  • …regularly does the symptom present? (Frequently, intermittently, rarely)
  • …warmed-up was the engine? (Cold, operating temperature, overheating)

Granted, not all of these questions will always apply; however, it is a best practice to be observant of these items and relay the applicable information when deemed appropriate.

Let's apply this to our grinding noise example from earlier to form a proper customer concern:

Yesterday morning on the way to work, I heard a grinding noise from the front of the car when I stepped on the brake pedal. The noise went away whenever I let off the pedal but returned when I pressed it again. As a result, I'm concerned that my brakes are going out and that, eventually, I won't be able to stop.


Determining the Cause of your Concern is the mechanic's responsibility. This is when the proverbial rubber meets the road; a mechanic will consider all the information you've provided during the "concern" step and then work on isolating the source.

Step 3: Verify The Concern

The first step is to "verify the concern," which is much easier to do with proper symptom context. If the concern cannot be reproduced, chances are high that any repair recommendation will be an educated guess that may or may not resolve the issue.

Some problems are frustratingly intermittent. Have you ever wondered why the problem doesn't ever occur when you need it to?

Interestingly, a somewhat laughable "Mechanic's Curse" implies that your concern will never be present for a mechanic.

Years ago, one of my customers was convinced that this so-called curse was confirmed after I rode along during three different test drives on three additional days without being able to experience her concern. Finally, at her wit's end, she jokingly offered to pay me to ride along indefinitely to "fix" the problem (to which I politely declined). The point is that sometimes these things happen at no fault of the mechanic or a supposed curse.

After the concern is reproduced, testing can begin.

Step 4: Test The Concern

The type of tests performed primarily depends on the failure's nature. For instance, a warning light concern typically calls for intricate circuit testing following the Original Equipment Manufacturer's (OEM) unique procedure. A rattle noise concern, however, is usually diagnosed through a series of physical looseness checks.

A seasoned automotive technician will use knowledge, experience, and reference material to determine the best way to diagnose your particular issue.

Additionally, I would be remiss not to touch on the "diagnostic machine" topic.

Somehow our culture has adopted the idea that there is a tool in a mechanic's arsenal that will determine the exact component that needs to be replaced; all that's required is to plug it into the vehicle, and "Voila!" On behalf of all mechanics worldwide, please tell us if such a thing exists because we'd buy it in a heartbeat!

The tool portrayed here is the On-Board Diagnostic (OBD-II) scanner. OBD-II scanners have an extensive range of capabilities which generally increase with unit cost. Whether $50 or $5,000, the primary purpose of the scanner is to retrieve Diagnostic Trouble Codes (DTCs).

DTCs can point toward an issue with a component, circuit, or system, but this is just a starting point for the mechanic. There's also no limit for codes, meaning that there can be multiple codes in one or more systems. It's not all that uncommon to have more than ten codes at the time of retrieval; hence DTCs are more like observations than conclusions.


Once the cause of your concern has been adequately isolated, the technician will recommend an action to Correct the issue.

This is often a physical repair but could also be an adjustment, recalibration, or software update. With the repair completed, it's time for the final step, which also happens to be the most overlooked and undervalued one; validating the repair.

Step 5: Validate The Repair

"Validating the repair" is close to "verifying the concern" from our previous section, but not entirely.

Repair validation includes confirming that your concern doesn't return and that no other issues have been presented. Failing to do this could result in a quick return visit, commonly referred to as a "comeback."

A comeback carries a certain amount of shame in the automotive repair culture. So while we want customers to keep coming back to us for work, we don't want it to be because we misdiagnosed or made any other mistake.

That said, not all comebacks result from workmanship errors; sometimes, an additional pre-existing issue can be masked by the original problem.

Regardless, a vehicle should be thoroughly test-driven following a repair to expose potential issues. Professional mechanics enjoy knowing that your concern has been resolved and that you are at least made aware of any other matter that may require future attention.

Let's recap:

  1. You notice the concern and document any helpful details
  2. The mechanic verifies the concern and isolates the cause
  3. The mechanic recommends a correction and resolves the concern

In conclusion, I hope you've found this article to be a helpful glimpse into how the vehicle repair process works. I genuinely believe that the customer's role is vital, and by having a better understanding of the steps included, you are empowered to help the mechanic more efficiently restore the vehicle to its proper operating condition.

About the Author

Cody H. is a Universal Technical Institute (UTI) Graduate, ASE Master Certified Technician, and former Honda Master Technician. Before joining the Wrench team, he repaired vehicles in independent and dealership environments and most recently provided warranty services for Nissan North America. Cody now provides technical insight for blogs, providing readers with an educated and transparent look into automotive maintenance and repair.

Get a free quote