Are you ready for Pass-Thru?

Dec. 20, 2016
Questions to ask oneself as Pass-Thru takes effect.

The Right to Repair Act will be an industry game-changer as manufacturers move towards web-based delivery of programming via Pass-Thru. The Right to Repair mandates that Original Equipment Manufacturers (OEMs) ensure their data is made readily available via the web.

This means that an interface standard designed by the Society of Automotive Engineers (SAE) to allow vehicles to be reprogrammed will come in effect. All vehicle manufacturers must afford the Independent Aftermarket/Specialists the ability to carry this out without the need for the dealer.

The one question that remains on many minds is whether or not they -- and the industry -- are ready for Pass Thru.

Here are some questions to ask to better understand whether or not you are in fact ready for Pass-Thru.

What does Pass-Thru enable you to do?

Pass-Thru has been around since 1996 and has changed a lot over the years. Looking forward, it will continue to change to adapt to new market standards.

Different manufacturers seem to have taken slightly different views on how best to implement Pass-Thru. For example, Mercedes only allows emissions relevant control modules to be programmed using a J2534 Pass-Thru Vehicle Communication Interface (VCI), and do not provide diagnostic functions, whereas BMW allows Programming and Diagnostics to be performed along many other functions to give the specialists as much help as possible.

It should be noted that even where OEMs have good functionality with Pass-Thru, it often falls short when compared with the functionality of the (OEMs) dealer tool. This should always be considered before investing in equipment for programming. Specialist shops and those who carry out a significant amount of programming should consider OEMs’ tools, whereas shops who only carry out occasional programming will be better suited to use a Pass-Thru VCI.

How good is your Internet connection?

Garages and workshops will require a stable internet connection to enable Pass-Thru. A high download speed is an advantage, as this will speed up downloading programming files and OEM updates to the respective Pass-Thru application.

Some manufacturers already require that the device being used for programming be connected to the internet during programming, and it is expected that more manufacturers will adopt this in the future. It is crucial that the internet connection is very stable. This is very important, as users do not want to lose connection during programming, as this can cause several control modules in the vehicle to fail. It is also advisable to hardwire your device to the Internet as opposed to relying on a Wi-Fi connection. Internet connection issues are a major factor in problems that are encountered when setting up Pass-Thru and in programming failures.

In addition to having a stable Internet connection, you should also check that it is secure. The introduction of the connected car has led to fears around vehicles being "hacked." To combat this, OEMs are putting ever more stringent checks on who has access to their software and, if you are using Pass-Thru, this will include you. If you have anti-virus software installed on your device, you will need to check this is compatible with the OEM’s Pass-Thru software. You should also make sure that your passwords for access to the OEM’s software and Wi-Fi network are different, and of adequate strength.

Do you have a battery support unit?

During programming, the vehicle needs to maintain a certain level of charge. Normally, this is 14.5V. This must not be changed in any way. Furthermore, it is very important to get the correct support unit.

A battery charger is not a support unit. While battery charger technology has improved over the years, voltage across the battery still cannot be regulated or stabilized. This must be stable when programming as the control modules will be programmed with new data. If the control module supply voltage fluctuates beyond 9-16V, it can cause a module to shut down and possibly corrupt the data. It can be very difficult to recover a control module that has been corrupted during programming and often the only remedy is to replace the control module with a new part.

What laptop should you choose?

There is a minimum requirement for the laptop/hardware on each manufacturer website, which can change at any given time, depending on whether or not the manufacturer updates its own individual systems. BMW, for example, is currently changing their operating system to ISTA 4 from ISTA 3, and the minimum requirements are now different. It is worth noting that the laptop many manufacturers recommend and use for their dealer tool application is the Panasonic Toughbook.

If you have a laptop that meets the requirement in the workshop and you want to use this for programming, there are ways to determine if it will work.

First, examine what other programs are running on this laptop. Determine if it is possible to have more than one manufacturers’ data on one laptop. While having more than one manufacturers’ software running on a single device is possible, each manufacturer does specify that theirs should be the only one loaded onto a single device. In the event of a programming failure, most OEMs are willing to help but one of the first questions asked will relate to what other software programs are loaded. This will troubleshoot whether or not they could be stopping programming from running properly. There are many questions to be answered before using the laptop -- this is just scratching the surface.

Which VCI should you choose?

There are many VCIs on the market. There are VCIs that are capable of programming all brands. A J2534 interface for Pass-Thru must meet standard requirements to allow certain modules to be programmed and to work across multiple brands. This is a good choice for repair shops that work on a variety of brands. Manufacturer interfaces are completely different and will enable greater functionality than a J2534 VCI. This makes them a good choice for specialty repair shops.

What else do you need to know about Pass-Thru?

The U.S. EPA regulation mandates that all OEMs must comply with SAE J2534 reprogramming from 2004 model year onwards for Powertrain ECUs.

Here is how J2534 has changed over the last few years.

J2534-1 -- Defines the emissions related control units (1996-2004).

J2534-2 -- Allows OEMs to add features for their own use. Future technologies could bring new requirements in both hardware and software.

J2534-3 -- Defines the compliance testing to establish whether a J2534 device meets the standard as laid out in J2534-1.

J2534-4 -- Defines recommended practices and needs that OEMs must disclose for application requirements, such as protocols, physical layers, J1962 connector pin selection (what’s on which pin?), network connections, Windows PC requirements, etc. This is a work in progress.

J2534 and Pass-Thru will continue to evolve over the coming years as more legislation surrounding the access and security of software in vehicles is implemented. The vehicles that are currently entering the aftermarket have a greater number of control modules and are increasingly complex. More replacement parts now require programming or coding to bring them into service, and OEMs are increasingly using programming as a method of repair.


In summary, perhaps the most important components of Pass-Thru are as follows:

  • It’s accurate – Guarantees the use of the latest data.
  • It’s secure – Makes certain that programming functions match the latest OEM security features.
  • It’s safe – Ensures that the vehicle (and driver) is programmed accordingly to meet OEM safety.

These three factors make successful Pass-Thru possible. Otherwise, there could potentially be an adverse effect on the insurance requirements of repair shops.

If you are already programming, you will find yourself doing more of it, and if you are not programming just yet, you will need to start quickly if you want to take jobs from the start through to their conclusion.

Better fasten your seat belts and get ready for the ride.

About the author

Tony Gill is group operations manager at Autologic Diagnostics, provider of the world’s first and only fully integrated cloud-connected vehicle diagnostic support solution. He can be reached at [email protected].

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