Advanced hydraulics testing for valve bodies: why there is still no universal solution for mechatronics assemblies?

This part 2 is a conclusion to our 2-part insight into the Transmission Control Module / Mechatronics Units testing. For part 1 - click here.

As people with scarce hands-on experience in the field of valve body rebuilding and testing we sought experience of specialists who have profound knowledge of both rebuilding technology and testing equipment production process. Alan Smith, Managing Director and Alexey Shihov, Hardware Engineer at Cottingham Engineering / Hydra-Test shared their thoughts with us during preparation of material for this article.

Hydra-Test technology of valve body / solenoid testing

Some of the earliest machines for advanced hydraulic valve body testing were produced by the UK manufacturer under the brand “Hydra-Test”, which through decades has gained wide renown among the industry specialists. These products were launched by Hydra-Test Ltd, a UK company formed in the early 1990s by Bob Fotheringham, who had been a distribution agent for Answermatic in Europe and UK. Despite being quality machines, Answermatic products lacked solutions to test domestic European VBs, and an updated designed machine with a wider test plate coverage suggested by Bob evolved into the “Hydra-Test” brand. It is worth mentioning that passing through multiple acquisitions over the years original Answermatic technology is now part of the Powertest company (with the acquisition of Superflow).

Picture of Answermatic machines

The first Hydra-Test machines were purely analogue rather than digital, which is only logical provided that they date back to 1990s. It is testimony to the build quality that some machines are functional to this day after undergoing refurbishment and updating to more recent standards appropriate for the digital era. There were number of variations of the machines over the years, however, testing method always remained the same: Hydra-Test machines allow users running a series of tests checking performance of a malfunctioning valve body at various gears and pressure inputs. If put simply, they emulate transmission performance of a driven vehicle.

Picture of Hydra-Test machines

Hydra-Test valve body test benches were primarily designed as an “End-of-Line” test solution to confirm and where required calibrate a rebuilt valve body. Using Data Acquisition the Hydra-Test tech team gathers performance results from a new or known good valve body to compare the rebuilt unit against. This is the key purpose of the unit, with ever expanding range of supported valve body / solenoid models. What is more, comparison against the master graph makes it possible for valve body rebuilders to determine the exact source of the problems - be it a damaged solenoid, a worn-out valve or plunger. It is essential to note that all these tests have always been related to hydraulic checks with electric checking of solenoids arriving more recently. TCMs / mechatronics are all excluded from the test circuit with the Hydra-Test machines.

Changes in the technology of valve body / solenoid testing in the course of 1990s-current days

Having undertaken research on Hydra-Test machine technology, we summed up the obtained data in the table below:

The key differences in machine generations were:

• data accuracy (highly influenced by the frequency of data capture and improved by the interpolation feature for solenoid control. This important feature allows reading of all incremental changes in duty cycle for PWM solenoids over a chosen time period - it means they are read exactly as they operate in the valve body),
• time for a single test (reduced with the advent of quick-fit hose connections and hardware and software improvements),
• degree of user friendliness to the operator, backed up by a profound training course too (with the latest HT-VBT Deluxe machine the operation is more and more intuitive with relying on available video and text guides being just a support),
• simplicity to discover an error in a valve body (notable contribution of higher data capture frequency, improved temperature control, and ease of data comparison with chart management).

The improvements explained above are continually ongoing with every generation model. Here are some thoughts on testing with TEHCM from Alan Smith, Managing Director of the company currently owning the Hydra-Test technology:

“After we perfected our own HTC-K controller we decided to investigate testing method to include the imbedded TEHCM using similar principles as incorporated by our previous controller-system supplier. It soon became apparent that whilst the actual technology was widely available, protocol sourcing was to prove a major obstacle. A study of customer feedback that have attempted testing this way in the past reported continual frustration with connectivity and reliability. This frustration has culminated in many operators simply abandoning this expensive equipment in favour of the tried and tested hardwire alternative. We strive to offer a complete ‘plug n play’ system where we carry out as much work in advance for our customers as possible. With the many thousands of differing manufacturers protocols to overcome, creating a universal system that would truly be consistent was not proving to be a viable option.

Over many years I have come to realise there are major differences between OEM testing methods and what is experienced in the aftermarket. A new components functionality can easily be confirmed whereas a component that has undergone wear and contamination issues is more complex. At Hydra-Test we aim to confirm the correct operation of the valve body and solenoids. By adding a third component in the form of the TEHCM can, and does, make operator diagnosis more confusing. If a TEHCM responds to the ‘wake up call’ it will shift the gears but this still doesn’t fully confirm all aspects. I spoke with a customer recently that tried this method for a while reporting that when he saw an issue during testing, he would then remove the TEHCM and perform the test again to eliminate it. His expensive investment then became a tool to check if it would respond to a ‘wake up call’, only if its protocol was included”

Attempts and failures to create universal solution for mechatronics units / TEHCM testing

When attempting a repair on a faulty mechatronics unit, first of all it is necessary to determine the source of the problem to establish if the fault lies within the electrical or hydraulic part of the unit. If you need to test the electrical part of the mechatronics unit, it is required to use a master (properly operating) hydraulic part. It turns out to be quite a challenging task, since there is a large number of modern automatic transmission models, which means owning a huge number of new mechatronics units on your bench to use as references. In this case, the only economically-viable solution is diagnostics and, possibly, repair of the mechatronics hydraulic part, which actually means working on the valve body component of the mechatronics unit assembly. With Hydra-Test VBT Deluxe for instance, they test the hydraulics of the valve body and the solenoids but the control units are excluded from the circuit, i.e. that Hydra-Test hardwire the machine to the solenoids and control unit is omitted.

Picture of HT-VBT Deluxe

This approach allows solving most problems, due to the fact that the main reason of failures of modern automatic transmissions lies in increased wear of hydraulic parts in the mechatronics unit, caused by the speed of gear shifting required for the driving comfort enhancement.

Nevertheless, many repair shops would like to offer their customers the mechatronics repair and rebuilding services too. In theory, this task does not seem so difficult: you take a faulty mechatronics unit, rebuild its hydraulic part, connect it to the computer, send several commands, analyze the response, and detect the problem. But in reality, from the very beginning you have to deal with numerous problems in the electric part of the mechatronics. As stated above, a modern mechatronics unit interacts with other vehicle components by means of CAN-BUS, and it must receive all the necessary information to start proper operation. The scope of required information is described by the internal exchange protocol. The problem is that the exchange protocols differ from each other depending not on the manufacturer only, but also on the transmission model. If you don’t have free access to the manufacturer’s data, you have to collect the data on a real car (in different modes of operation). This is a time consuming, labour intensive process. A certain American gearbox specialists had to buy a car equipped with a new automatic transmission in order to obtain the exchange protocol data for this transmission. It took about a month to collect and process the required information. In addition to these technical difficulties, the automakers started coding and encrypting the information transmitted via CAN-BUS to confront third-party repair shops offering repair services for modern mechatronics units. Some mechatronics units have a built-in service (technological) mode of operation. Thanks to this mode you can control the mechatronics unit without the need to simulate the exchange of data with other components of the vehicle (but it is available in certain models only). However, these gearbox specialists from the USA had to deal with the situation when the mechatronics unit, successfully tested using the technological mode of operation, still gave an error message after being installed on the vehicle.

However, these gearbox specialists from the USA had to deal with the situation when the mechatronics unit, successfully tested using the technological mode of operation, still gave an error message after being installed on the vehicle.

Another problem when testing the mechatronics is caused by the fact that the design of some of the mechatronics models includes not only electronic and power components, but also some types of sensors (for example, the Hall sensor). In this case, you need not only to create the simulation of data exchange via CAN-BUS, but also to install electro-mechanical parts and assembly units, which simulate the operation of the similar vehicle units. For example, for the 6HP transmission you need to create some external simulator for the output shaft rotation. The biggest issue is that there are multiple protocols employed for the TEHCMs of one type. This drastically multiplies the complexity of the task. As an example a transmission rebuilder from the USA provided the figure of 1208 different flash files for just the 6R/6L units by FORD.

Summing it up, it is logical to conclude that in order to allow for truly efficient mechatronics units or TEHCM testing, the only true solution is to have a joint venture project with manufacturers of ATs. Certainly, it will not happen anytime soon (if ever) due to multiple understandable reasons. Let us delve further into the mechatronics testing and some of the existing solutions, which are by no means universal, but still ease AT rebuilders’ life a little.

Summary: mechatronics testing myth debunking and real diagnostics approaches

Known and existing testing solutions on the market

We spoke to an automatic transmission repair company from the UK and they had good results on the 6DCT and 6T40-45 mechatronics by using the new LAUNCH scanning tool. They also advised to check out HELLA and the latest SNAP ON tools to see what would satisfy current testing needs. Quality advice can be sought from large companies covering a huge market. For instance, we suggest checking M2K Inc’s page covering a vast array of scanning tool for multiple makes.

Why the so-called 'universal' solutions are just a myth

Due to the fact that most of failures in mechatronics units are mainly caused by wear and damage of hydraulic components, prominent equipment manufacturers focused on development of the first-rate solutions for hydraulics testing with valve bodies. So-called ‘universal’ solutions, currently presented on the market, in reality provide only a partial solution to the problem – for instance, as described above one of them can test BOSCH ZF's but not the Continental units. The creation and constant updating of a universal set of tools for testing the entire range of mechatronics is economically inconvenient due to the high total cost for the end user.

Automakers continue to improve existing mechatronics solutions. The simplest way to improve the quality of mechatronics units operation is to sophisticate the algorithms of their operation, change the principles of processing and analysis of data from sensors and systems of the vehicle. As a result, transmission repair specialists may face a compatibility issue when testing constructively similar mechatronics units (with different years of production) with the help of ‘universal’ tools.

On plentitude of data exchange protocols as an obstacle for a single solution for a single make

This problem is caused by the presence of a wide range of different exchange protocols (depending on manufacturer and transmission model) via CAN-BUS. Many protocols are very similar in terms of structure (especially within the same family of automatic transmissions). This led to advent of so-called scanning devices, which send standard commands (by the method of trial) and wait to receive standard responses from the automatic transmission being diagnosed. However, it is naive to expect that this approach will be 100% efficient even within the same family of automatic transmissions.

Advice to transmission specialists wishing to test mechatronics units / TEHCM

If the problem of mechatronics testing is very urgent, then the only way is to resort to practical use of several ‘universal’ solutions from different manufacturers. Some solutions will be efficient, for example, for American automatic transmissions, others – for European or Japanese transmissions. You have to be prepared for this scenario. Be ready to devote much time to experiments and search for the information on mechatronics testing on the Internet. You shall definitely employ separate tools for hydraulic testing on valve bodies and OEM scanning tools to check your modules and work on them. Working on fine ties with fellow specialists in the gearbox repair business will bear fruit since quality practical advice is only provided to members of closed communities.