Understanding Toyota's vehicle control history

Aug. 1, 2019
Data is essential in performing a competent diagnosis. Toyota's VCH provides a level of data that has not been accessible to the technician in the past.

The Toyota Techstream scan tool offers technicians the ability to access an amazing wealth of information from vehicle electronic control units. On newer model Toyota and Lexus vehicles, the ability to access Toyota Vehicle Control History VCH) information is a valuable tool in no-code diagnostics. The VCH data also provides some incredible diagnostic data for technologically advanced systems such as Toyota safety sense.s

The first time I ever attended a factory Toyota course, the instructor got on the subject of what he described as a black box technology, similar to that of today’s commercial airplanes, that store relevant data related to a crash should one occur. This black box data was only accessible via a Toyota field engineer and was not accessible through a scan tool. I can remember thinking how nice it would be if that data was actually available to technicians in some form as there are many times as technicians that we just simply don’t have enough information to properly diagnose and repair a vehicle. Fast-forward ten years and the idea of accessing ECU data that is not associated with a DTC is now becoming a reality on Toyota and Lexus Vehicles.

Vehicle Control History provides Engine Control “X” codes without setting a DTC – a great resource for no-code diagnostics.

Toyota has utilized Event Data Recorders (EDR) since 2000 when it began a rollout across the product line. Today, approximately seventy percent of the Toyota’s in the US are equipped with this technology- the subject of a 2016 Society of Automotive Engineers white Paper entitled Event Data Recorder Developed by Toyota Motor Corporation. The Toyota Event Data Recorder was developed to collect several collision analysis data parameters including pre-crash, side crash, rollover and pop-up hood pedestrian data. In addition to these parameters, Toyota also collected Vehicle control history data in a non-crash, triggered recording system. Federal regulations stipulate that this data must be available via a commercially available tool and Toyota worked with Bosch to utilize the crash data retrieval tool or CDR. Recently, Toyota began making some of the data available via their Techstream scan tool.

In the aforementioned white paper, Toyota stated that they felt that the evolution of this technology was forthcoming. For us as technicians, this is just the tip of the iceberg into how this data might help us.

HV operation history

Imagine yourself as a service advisor at a Toyota dealership in a busy metropolitan area in which a car count of over 100 vehicles is a normal day. Toyota has just announced a new model of the Prius and over twenty of these vehicles were delivered this week alone. The shifter technology has changed from previous model years and now includes a joystick shift function that is difficult to operate for some customers. After delivering the new vehicles to the customers, several have come back to the service drive complaining of transmission and shift related issues. The technician assigned to the repair order test drove the vehicle and found it to be operating normally and upon performing a Techstream health check there were no diagnostic trouble codes found in any of the modules. The service advisor reported the lack of findings back to the customer who is now displeased with the product and the dealership because the experience they had was perceived as a problem. In reality there may have been an error on the part of the customer in operating the vehicle.

The above scenario is a perfect example of how EDR data could be potentially used. In the past we have relied on a DTC in order to have a diagnostic game plan. A DTC gave us a code-set criteria and also brought with it freeze frame data. However, when a DTC did not set, we were forced to try to duplicate the concern. Duplication of a customer concern can be a wild goose chase that often results in the famous “no problem found” report back to the customer.

A Group 2 VCH Data capture displays twelve distinct freeze frame data points before during and after a triggered VCH event.
A group 3 VCH Data capture reveals slightly less information than a group 2 while a group 5 will store only one data point.

In 2015 when the 4th generation Prius was introduced; Toyota also included some enhanced scan tool functionality known as HV Operation History. This function allows the technician to access some very interesting data from the data list within the hybrid control ECU. This data is of particular interest when a scenario like the above-mentioned shift concern or in the event of an inability to ready on occurs combined with no DTC’s present. Specifically, the Techstream software is looking for abnormalities in driving conditions or other non-driving abnormalities that it sees as an issue but would not set a code for.

The beauty of this information is that it is referenced to a point in time within the data list. The HV operation history data stores “last” and” before last” occurrences of the particular data being viewed. The “last” data indicates the last key on cycle in which the data occurred. The “before last” data indicates the previous occurrence and its related key cycle. The data also references how many occurrences of the abnormality occurred on the related key cycle.

As an example, if the customer who reported shifting problems with the aforementioned Prius had last experienced the problem a week ago and travels to and from work with the vehicle, you could assume that a week’s worth of driving would be around 14 key cycles ago. If the technician retrieves data from this occurrence they will theoretically be able to match the data to the customer’s experience. Once confirmed, the advisor can communicate to the customer that there was an erroneous operation of the shifter and not a problem with the vehicle.

VCH Data is available on Toyota and Lexus vehicles through the Utility selection menu.

This is a huge time savings in diagnosing Hybrid vehicle customer complaints.

P1604 – Startability malfunction

A few years back I noticed a P1604 DTC on my 2013 4Runner. There was no MIL illuminated on the dash and I was not having any issues with the vehicle. I happened to be researching material for an upcoming class and noticed the code while performing a health check. Upon further research I discovered that a P1604 indicates a “Startability malfunction.” According to Toyota Technical information: “This DTC is stored when the engine does not start even though the STA signal is input, when the engine takes a long time to start, and when the engine speed is low or the engine stalls just after the engine starts.”

After reading this I realized my startability malfunction came as a result of my removing my foot from the vehicle brake during engine cranking which resulted in a no-start.

So why does Toyota provide a code single for a wide variety of circumstances? Well, it comes down to data. Imagine you are Toyota’s technical hotline and every day technicians of all different levels of experience are calling for assistance with difficult diagnostic scenarios, many of which have no related DTC. The beauty of the P1604 was that it created a DTC and with that DTC comes valuable freeze frame information. Data makes life easier for all parties involved in the diagnostic process. The P1604 by design is a fantastic tool for those in the independent repair market when diagnosing no-code difficult starting concerns. As a note: be sure to diagnose other DTC’s first as many times a P1604 will set as a companion code as a result of another problem. For example: If there is a code present for a MAF sensor related problem along with a 1604, diagnose the MAF code first.

A Query of the VCH Utility menu reveals a list of triggered events with related time and key cycle information.

Engine-related VCH data

Vehicle Control History Data is becoming available on Toyota vehicles and is available across multiple ECU’s. This vehicle control history information is a function that captures and stores data based on a specific vehicle behavior. The VCH data is incredibly useful and is quite similar to the concept of the P1604, however, VCH data may be available to the technician without storing a diagnostic trouble code.

Selecting a specific VCH event reveals related data.

As an example, the 2018 MY Camry was a complete redesign of the Camry platform. With the redesign came VCH data for the Engine Control Module. The VCH data is available through the Techstream Utility menu after performing a health check of the vehicle. The VCH data is a revolution in diagnostic information.

One of the issues with a P1604 DTC was that there were multiple reasons, or what we refer to as code-set criteria, that resulted in a code. The problem with having multiple symptoms that could result in a single DTC is that time is of the essence- We simply don’t have time as technicians to properly diagnose in most cases. VCH data further narrows our diagnostic efforts by providing a subset of data, codes and freeze frame information that are not linked to diagnostic trouble codes. Think of this as data for no-code diagnostics.

As an example, The P1604 code has been further broken down within the VCH utility. Instead of simply setting a startability malfunction DTC, VCH provides sub-codes that can indicate in a more specific manner why the vehicle didn’t start:

  • X0800 – Engine Stall
  • X0803 – Engine Stall – Compression leakage
  • X0810 – Engine Difficult to Start – Starting Time long
  • X0811- Engine Difficult to Start – Engine Stall Immediately after starting
  • X0812 – Engine Difficult to Start – Immobilizer

In addition to the “X codes” VCH data will also include enhanced freeze frame data related to the triggered event and will often include the ability to graph data over a period of time before and after the triggered event.

While it seems as though this information has been provided to ease the diagnostic complexities within the franchise dealership model, the wealth of information it provides will certainly provide independent technicians a wealth of information when diagnosing Toyota and Lexus vehicles in their facilities.

A VCH event triggered by ABS activation reveals the related data at the time before during and after the event.

VCH for Toyota Safety Sense

In last month’s Motor Age, Toyota Safety Sense was covered in detail. The TSS system utilized multiple inputs as well as control unit algorithms that enable the vehicle to assist the driver. The complexity of these systems cannot be understated. As a result of the ability to access VCH data for these systems, Toyota has been able to analyze and publish their findings as they relate to autonomous braking.

As an example, an SAE white paper entitled: The Accuracy of Vehicle Control History Data During Autonomous Emergency Braking was published in April of 2018. This paper points out the level of detail available through VCH data. If you are interested in a deep dive into VCH data analysis, it is worth the price of purchase and is available at a discount to SAE members.

Locating VCH data

As mentioned, there are multiple ECU’s that store VCH data. In the Hybrid Control ECU, the HV Operation history is located in the data list.

For Engine, Body/SRS Airbag related VCH data, the utility menu for the respective module will be utilized.

The data stream within the saved VCH event allows the technician to overlay graphed data.

Please note that the amount of available data for VCH will be dependent on what Toyota refers to as a data group. Each triggered event has a related data group and in turn, each data group has a number of data parameters that it will record.

To be sure on what data should be available, consult the Toyota service information related to vehicle control history.

The wealth of information available from VCH data to technicians in the independent repair market makes another strong case for Techstream factory tooling when diagnosing Toyota and Lexus vehicles. This information at the time of testing was not available through aftermarket scan tool platforms. As has been pointed out in previous MA articles, Techstream tooling and subscriptions are amongst the least expensive in the business with interfaces starting around $500 and subscriptions available in 2-day or yearly formats at $65 and $1295 respectively.

 Data is essential in performing a competent diagnosis. Toyota VCH provides a level of data that has not been accessible to the technician in the past.

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