Pre-Repair Scans and Post-Repair Scans: Timing is Everything

Pre-Repair Scans and Post-Repair Scans: Timing is Everything

Without a scan being done before repairs begin and after repairs are complete, the time and energy you’ll need to spend on diagnostics will multiply.

With the ever-increasing amount of electronics being added to vehicles, the importance of pre-repair scans and post-repair scans cannot be stressed enough. 

The number of systems that are networked together in current vehicles is amazing to all of us in the collision repair industry — and this trend does not show any signs of letting up. This has spawned an entirely new breed of technician and launched an industry within an industry. No facet of the repair industry has escaped the changes to the processes required to repair vehicles today. Collision, mechanical, glass and even paintless dent repair have all seen changes — and I could name more. 


This has been happening for a minute now, and we’re starting to see that the lifespan of these systems may be a concern to the repair industry. Variables such as road use, environment, crashes and other factors affect the life and service of these systems. 

As the systems are all networked together, it’s critical that they all communicate correctly. When one system or even one sensor is not functioning correctly, a diagnostic trouble code (DTC) is filed in the system memory — which has a serious impact on what’s happening inside the vehicle. Components subject to end of life due to these variables will affect the repairs you’re being asked to complete. Knowing what is collision-related (or the result of damage you’re being asked to repair) and what is not related will be critical to both you and your customer. Also, unrelated prior damage (UPD) will become more common in vehicle electronics.  

Where It All Has to Start

Scan tools are like X-rays for the human body — they allow us to see what’s going on inside. Without this insight, we’re only guessing at what will need to be repaired, replaced, aimed, coded, programmed or calibrated. Without a pre-repair scan being done on a vehicle, we may not even be able to identify what systems are in the vehicle. The VIN is not always a reliable indicator of whether the vehicle is equipped with a particular system. Even then, it may take a physical inspection to determine if a vehicle is equipped with a system or not.    

For a pre-repair scan to be of value, the following factors must be taken into consideration: 

  • It must be completed before disassembly or any work is ever started on the vehicle.
  • There must be correct power for all systems to register; a battery maintainer is the best option.
  • Updated or correct software must be used to complete the pre-repair scan.
  • The correct vehicle communication interface (VCI) must be used to communicate with the vehicle.
  • The scan must be saved and uploaded to the repair order.

When all of this is complete, we have a record of the condition of all the electronics in the vehicle before any work is started or completed. This offers a “ground zero” starting point if diagnostics are needed to find a condition that exists in the system. Without the pre-repair scan, more time and effort may have to be expended in diagnostics, creating a needle-in-a-haystack scenario. 

The pre-repair scan will show if the problem existed before or was created during repairs. The process of repairing a vehicle will create DTCs in the system; removing components and moving vehicles or just applying power back to the vehicle will create these codes. Knowing what was preexisting to the repair will aid in diagnosing the problem tremendously. We all know that, for years, many shops just threw parts at vehicles to try and get the right combination to fix the problem. In today’s vehicles, that method is too costly and still may not correct the situation. 

Throughout the repairs, parts are going to get removed and replaced or removed and reinstalled. Many of these parts will need to be tested, coded or programmed. An in-process scan done by a technician to find relevance to the parts he or she is working on by no means should be used as a pre-repair scan; at that point, too many parts have been removed and replaced or reinstalled. This in-process scan should be done to make sure the focused parts are not affected by the current DTCs and allows the coding, programming or calibrations to be completed. Examples include taillights equipped with radar, headlights, transferring modules between old and new parts, and blind spot modules. 

In cases of radars, an aiming procedure will be required prior to assembly. This may require the correct software to complete this task, as well as a digital angle finder. Often, the aiming procedures will be required before assembling bumper assemblies and may not be considered a calibration. 

The Key to Reducing Returns

After all the repairs are done and the vehicle is assembled, it’s time to set up for the calibrations. Calibrations validate that the repairs were done correctly. The drawback is that sometimes the calibration or relearning process is not done correctly, or there is an issue that reveals itself a few key cycles later. 

Remember, you can have a successful calibration, but if the targets, environment or automaker’s prerequisites were not correct, the vehicle will not perform correctly and will take a few cycles or test drives for the algorithm to figure out there is a problem.

Sometimes, a short time later, the customer will get a light on the dash indicating that a system is not functioning correctly — which will cause him or her to return the vehicle to the shop. This scenario can be eliminated if the shop performs a final test drive for some distance after every process is complete versus a quick run around the block. This drive will give the vehicle electronics time to react, identify any issues and set any DTCs that are reoccurring.   

The other reason a shop must perform the final post-repair scan is that although services such as coding and calibrations were done, the shop and personnel were still working with the vehicle and possibly performing procedures either needed or still needed after the calibrations. This will not be found until after the customer drives the vehicle if no final or incomplete test drive was done. Before and after the test drive, these newly caused codes need to be documented, researched and cleared, if possible. If they’re reoccurring, it’s important to determine if they were collision-related, UPD or created during repairs. This is where the pre-repair scan becomes so important to compare to the post-repair scan to diagnose the issue. Without this, the phrase, “It worked before I brought it in,” may lead to you footing the bill for repairs to appease the customer. 


I know that all this information about pre-repair scans, post-repair scans, calibrations programming and coding as well as diagnostics is difficult to keep up with. Having a scan tool and maintaining updates is a task that must be done or checked every day. Vehicle manufacturers are changing the game every day on their vehicles, adding systems and changing access to the vehicle. 

If you’re doing scans in-house, you know what the process is. For those of you who are subletting, it takes coordination to complete all the tasks required to repair the vehicle correctly. That too is a never-ending thought process to schedule. 

Make no mistake: The time and effort to do calibrations in your shop, in addition to altering space, will increase in your shop every day. Plan and research your needs. Never short-cut on the steps and the order they need to be done. I see so many wash bay diagnostics being done in the industry where issues with vehicle electronics are found right before delivery to the customer, and that will only lead to headaches.

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