What is a Pass-Thru device?
A pass-thru device is used in conjunction with a computer to reprogram ECUs through the OBD port.
The Background to Pass-Thru
Every control unit contains ‘software’ or a ‘program’ in its microprocessor, which manages the system elements.
In the case of the engine control unit, this ‘software’ looks for the best operating conditions according to the information received by the sensors to optimise the maximum fuel consumption and try to emit the minimum of polluting emissions possible.
It is usual for the software installed in the control units to be replaced by updated versions in order to optimise the operation and/or correct errors.
This work was generally carried out in an official main dealer workshop since the appropriate equipment was too expensive and difficult to obtain.
The SAE J2534 protocol, known as Pass-Thru (Pass-through), was introduced in 2004.
It is a communication protocol that allows any independent technician using low-cost equipment to access a vehicle to be able to: update the software of the units, install the latest improvement to each manufacturer, and perform all operations necessary for the replacement of a component, especially the system related to emission polluting gases. This work aims to ensure the vehicle’s operation without breakdowns and with maximum efficiency of the combustion engine and thus improve air quality, especially in large cities.
This technology allows independent workshops to perform this work at an affordable cost. However, these processes require special knowledge regarding safety recommendations since they can potentially cause irreparable damage to the control units.
The European Union adopted the J2534 Pass-Thru protocol to comply with the Euro V/VI regulation.
The SAE J2534 protocol is split into two sub-protocols:
1. SAE J2534-1: Defines the characteristics of a device that allows the repair of components related to anti-pollution systems.
2. SAE J2534-2: Defines the characteristics of a device that allows the repair of all the systems of a vehicle.
The manufacturer decides which protocol is applied to their vehicles.
Requirements for Pass-Thru
Requirements for the application of the Pass-Thru can vary according to the manufacturer, but in general, for correct operation, any technician who wishes to connect a vehicle with the official server of the brand must have the following:
A Modern Computer
– A fairly modern computer with a Windows 10 operating system. It is usual to require several Gigabytes of space on the computer’s hard disk (between 5 and 500 Gb).
– LAN / Ethernet / RJ45 Connector
– Minimum of 1 USB 2.0 port
– Basic computer programs: Internet browser, Adobe Reader, Adobe Flash etc. (Dependent on brand and their support)
– Important!
– It is highly recommended to disable any antivirus software installed on the computer and disable all functions of battery saving, hibernation etc. In turn, both the computer and the communication head (VCI) must have their own power supply.
VCI
VCI (Vehicle Communication Interface), diagnostic head compatible with the SAE J2534 standard (Pass-Thru).
Not all Tools that list J2534 have been Tested and approved, and some tools are listed as compliant or ready. Don’t forget J2534-1 & J2534-2.
High-Speed Internet
The programming process of a whole vehicle can take more than 3 hours, and the speed of the internet connection is a decisive factor (where there is a normal connection, the process can also be carried out after a long waiting period).
Although it is not strictly necessary, it is HIGHLY RECOMMENDED that both the connection of the VCI interface to the computer and that of the computer to the internet network be made by cable, avoiding communication via Bluetooth and Wifi. The goal is to achieve a stable connection that is not disturbed by external interference.
External Power supply/stabiliser
A stable battery voltage is vital without current peaks during diagnosis; otherwise, the process can be interrupted, and irreversible damage to the control units may occur.
In the case of new JLR vehicles, a power supply capable of providing 120 Amps in any condition is required. Please also note that some programs have a maximum as well as a minimum voltage limit.
Programs for Each Manufacturer
Pass-Thru is a process that connects the vehicle directly with the server of a specific brand, regardless of the multi-brand device’s diagnosis program (the interface supplied with the multi-brand diagnostic equipment only performs the “bridge” function). So the user of the Pass-Thru protocol must have previously downloaded an application provided by the manufacturer on which you want to work (for some brands, the diagnosis is 100% online and does not require any program to be downloaded).
This process involves: downloading a file of several GB (between 5 and 60 GB), registering an account, understanding the program’s operation and paying for the time of use (you can pay by the day, week, month or year).
For the use of diagnosis programs of some manufacturers, it is necessary to have an electronic security key (usually a USB stick). The key is obtained during the registration period, which can take several months.
Advantages and Disadvantages of the Pass-Thru System
As with everything, the Pass-Thru system brings benefits to the workshops that work with any car manufacturer but also has its drawbacks.
Advantages
– Lots of technical information on a particular vehicle can be found using its chassis number.
– Information is available 24 hours a day, 365 days a year because the server is nearly always operational.
– Information provided is always up-to-date and is the same as available to the main dealer.
– Saves time because the steps to follow are available for each repair process, and TSB Bulletins can help with effective diagnosis if module updates are required.
– Saves costs on Hardware VCI units as only one device is required for multiple vehicle brands
Disadvantages
– You must have a good internet connection, preferably Hard wired LAN. Otherwise, the diagnosis process takes several hours, and irreparable damage can be caused to the control unit if there are interruptions to the connection.
– Difficulty accessing information as each brand uses different terminology.
– The technician must know how to operate each brand’s program and navigate the information structure.
– It is not possible to obtain information on some models prior to Euro V regulations.
– To register and access certain levels of information, some manufacturers request additional certification from the workshop, such as civil liability, activity licence (VAT), criminal record, and official ID for the technicians who will have access to the platform. e.g. Driving licence or passport.
– Before using the manufacturer’s original program, it must be installed and updated. The program is usually several GB (between 5 and 200) and once installed, the user must register. Installation usually lasts several hours, and often the process is complex and not well-explained.
– Obtaining a licence to use the program can take several months.
– Some manufacturers provide an electronic key (sent by conventional mail eg USB) after registration to access your server.
– Installation of a program and obtaining a licence do NOT provide a short-term solution.
– Payment is necessary each time the program is used.
– Subscription prices range from €5- €40/hour to €1,000 – €4,000 /year. This depends on the manufacturer and the level of information required).
– Often, the level of program operations is not known until access is paid for, and the repair steps are completed.
– In some cases, after paying for access to a specific level and arriving at the time of diagnosing a system, the server frequently requires another payment to perform further operations (security restricted).
Conclusion
Although there are a few hurdles and things to be aware of, with the right set-up and knowledge, Pass-Thru diagnostics can be a relatively simple and inexpensive stepping stone into the world of dealer diagnostics. More informmation about car diagnostic tools, please visit our website: https://www.obd2tool.com