CSS test USB Autoscope IV. Lecture of Andrew Shulgin, Part 1.

00:18 - As I gained experience, I gradually learned to choose the right diagnostic device, which, in each specific case, made it possible to find the problem easily and quickly. In some cases, just a multimeter was all that was needed. In other cases a scan tool was required, in still others it was necessary to use a test bench to check fuel injectors or some other equipment. Over time, the list of my equipment got longer and longer. I even used the Dollar bill diagnostic method sometimes.

00:54 - You simply hold a piece of paper against the tail pipe of the running vehicle. A cylinder misfire will be readily indicated. A quick and dirty method, simple to use, but not very accurate and you don’t know which cylinder or why it is misfiring.

01:09 - If a misfire is suspected, a scan tool is connected and the error codes, commonly referred to as DTCs for Diagnostic Trouble Codes, are read from the PCM Powertrain Control Module vehicle computer memory. DTCs P0301… P0312 directly indicate the number of the misfiring cylinder. As an example, P0301 indicates a misfire in cylinder #1, and P0302 a misfire in cylinder #2. Unfortunately, there are cases where the engine control unit cannot determine specifically which cylinder or cylinders that is or are misfiring.

In these cases the computer will set a P0300 which is interpreted as random or multiple cylinder misfire detected. The misfire code itself does not provide any insight as to the specific reason for the misfire. There are four areas that can cause a misfire and/or misfire code to set, namely; The ignition system. The fuel system. The engine mechanical condition.

02:14 - Additionally, the code may be falsely set by items such as the drive belt, water pump, air conditioning compressor, various bearings, or simple software problems.

02:25 - The PCM’s software can detect and display changes in the crankshaft’s angular velocity or speed if you will. The crankshaft speed should speed up after each cylinder’s firing. If it does not, a misfire is indicated. The PCM knows which cylinder that did or should have fired and can set the approriate DTC. If the misfire is occurring at idle, a very efficient method for troubleshooting is to swap, one at a time, the ignition coil, the spark plug, spark plug wires (if used), or even the injector with a cylinder that is not experiencing misfires.

If the misfire moves to the other cylinder, as indicated on the scan tool, the defective part is found.

03:09 - Diagnosing by parts substitution is sometimes referred to as “swaptronics” The parts substitution method works well if the misfire is consistent and repeatable. It also depends on the PCM’s software being able to consistently identify the misfiring cylinder, especially if the misfire is random and/or inconsistent.

03:30 - Despite the presence of a variety of equipment and experience with it, I still often encountered difficulties in the diagnostic process. Often there were cases when, even after spending a lot of time on diagnostics, I could not, without partial or complete disassembly of an engine, unambiguously determine which system was malfunctioning. Was it the fuel injection system, the ignition system or engine mechanicals. Intermittent and random problems are by far the most difficult and time consuming problems to diagnose.

I learned early on in my career as an automotive technician that a major contrubuting factor to a technician’s and shop’s success is the ability to diagnose problems quickly, efficiently, and correctly. If a problem is misdiagnosed, valuable time is wasted, parts may be uneccesarily replaced, vehicles go unrepaired, and the customer looses confidence in the technician’s and shop’s abilities. Also, the shop may have to pay for the uneccesary parts. Some of the components on modern vehicles can be very expensive.

04:44 - So, I realized that timeliness and accuracy in the diagnostic process was extremely important and set out to develop diagnostic techniques that would fulfill these needs.

04:54 - And by 2008 I succeeded - I developed a technique I called CSS Test.

05:01 - This test allows to identify misfire cylinders quickly and easily and indicates the area of origin of the problem. It allows you to obtain the following information without disassembling the engine and related systems:  compare the dynamic compression of the engine cylinders. check the functionality of the ignition system not only as a whole, but also in relation to a specific cylinder number. check the operation of the fuel injectors. check the operation of the ignition timing subsystem.

identify defects of the reluctor wheel. evaluate the crankshaft position sensor signal level.

05:39 - 12 years have passed since then. During this time, my technique has been frequently improved. Now it is used in many countries around the world and of course I am always pleased to receive positive reviews about the software. I continue to improve the CSS test, making changes that will improve the reliability of the automatic signal analysis function. As an input signal, the crankshaft position sensor signal of the tested vehicle is used. This signal contains very detailed information about the nature of the engine crankshaft rotation.

This rotation occurs and changes as a result of the fuel/air mixture combustion in the engine cylinders. For example, the crankshaft slows down as the charge in the cylinder is compressed and speeds up when combustion takes place. As a result of rather complex mathematical calculations, I was able to mathematically analyze the crankshaft position sensor signal and obtain information from it about the nature of the events in the cylinder and the ability to present the data in an easy to read and understand format.

06:47 - In addition to the crankshaft position sensor signal, it is required to record a synchronization signal from the ignition event in cylinder #1. This signal indicates the moments of time when the piston of cylinder #1 is near the top dead center, and allows us to distinguish the events in one cylinder from the events in other cylinders.

07:07 - I developed the CSS test algorithm based on the USB Autoscope motor tester. The script has been built into the software of all modifications of the USB Autoscope. Now I am using the latest modification of this device, my further recommendations will relate specifically to the USB Autoscope 4. On almost any engine, the crankshaft position sensor signal should be recorded as a signal source about the instantaneous engine speed.

07:38 - The ignition pulse of cylinder #1 is used on a gasoline engine as a synchronization signal with the moment of ignition of the fuel-air mixture in cylinder #1. It should be noted that on both gasoline and diesel engines, in case of difficult access to cylinder #1, you can use the synchronization signal with any other cylinder; however, in addition to the firing order, you will need to specify the number of the synchronization cylinder. Initially, I had to manually configure all the parameters each time before each measurement.

Often, the result was not the best for the reason that, due to insufficient care during the configuration of the device, some of the parameters were not set correct. In this case, you had to start the device again, configure it correctly this time, and repeat the test. And this required additional investment of time. In order to exclude the occurrence of errors when setting up the device before taking measurements, the optimal parameters of its operation were saved and built into the “Modes” menu of the USB Oscilloscope program.

At the moment, there are 3 preset modes: “CSS”, “CSS 4 channel” and “CSS Diesel”.

08:54 - All of them are combined under one tab and are available through the menu “Modes => CSS”. For a standard CSS test on a gasoline engine, use the “CSS” mode. For a standard CSS test on a diesel engine, use the “CSS Diesel” mode. The “CSS 4 channel” mode is intended for extended testing of the engine management system using additional channels of the motor tester and the capabilities of the algorithm. We will come back to this additional feature at a later time.

And now, using a practical example, we will consider the order of the test. We install the black capacitive probe on the high-voltage wire of cylinder #1.

09:43 - A connection to the crankshaft position sensor is required to obtain the sensor signal. We connect the black alligator clip of the power cable to the vehicle body ground. Making the ground connection at the “minus” terminal of the battery is not recommended due to the presence of a high level of interference on this terminal, especially when cranking the engine. We connect the red alligator clip of the power cable to the “plus” terminal of the car battery.

Open USB Oscilloscope and turn on CSS mode. We start the engine and let it idle.

10:26 - In the program window, turn on the recording and after a couple of seconds raise the engine speed to 3000 RPM. We close the throttle and wait for idle speed, after that we sharply open the throttle completely. After reaching 3000 RPM, we turn off the ignition, while the throttle valve should remain open until the engine stops completely. If the throttle is equipped with an electronic throttle valve, a way to keep the throttle open may be needed, but try it.

Turn off waveform recording. Let’s analyze the recorded waveform, for this, in the USB Oscilloscope program window, select “Run script”. As a result, we get several report tabs. Tab “Report” – text. Here you can see the formula of the reluctor wheel 60-2 and the number of teeth from window to TDC 15. “Efficiency” tab - shows the efficiency of each cylinder at different stages of measurement. The “Timing” tab shows the relative ignition timing depending on the speed and load.

The “Toothed disk” tab displays the reluctor wheel and crankshaft sensor parameters. Let’s go back to the “Efficiency” tab. Here you can see that the compression in all cylinders is the same. The ignition system is working properly. There are also no problems with fuel supply.

12:04 - Consider separately the operation of each cylinder, it can be seen that all the engine cylinders worked the same at all stages of measurement. .