Automotive Technology Course | Electronic Throttle/Drive-by-Wire Testing

Automotive Technology Course | Electronic Throttle/Drive-by-Wire Testing


you you you this is the drive-by-wire throttle control system this system employs a double throttle position sensor as well as a double accelerator pedal position sensor as we can see on screen an electric motor is attached to the throttle plate shaft this electric motor is commanded by the ECM or the throttle control computer according to the pedal position sensor input and the feedback from the double TPS there is no physical connection nor cable between the driver and the engine with these type of system the dual or sometimes triple TPS sensor is manufactured in this way for redundancy or in case one of the potentiometers fail in such a case the computer would use the redundant TPS to allow the driver to reach the nearest repair shop albeit at reduced performance drive-by-wire systems are employed for a few reasons one of these reasons is that the ECM is in full control of the throttle activation this falls within the principle of doric management systems torque management only means that the engine is going to do whatever the ECM wants it to do and not the other way around in regular fuel control systems with throttle cable the driver presses on the accelerator pedal the throttle plate is actuated and the throttle position sensor gives an indication of aperture once the ACM sees that then it will make the appropriate Corrections as necessary again there is a specific reaction lag time between the computer receiving and making the proper decisions and adjustments this poses a problem when it comes to fuel efficiency and emissions output from the engine better own a ascension operation although very short has to be absorbed by the catalytic converter and the rest of the emission control components over time and multiplied by millions of cars on the road it has up the drive-by-wire system is employed in order to protect the catalytic converter raise emission standards and give the ECM a wider control of the torque produced by the engine the process of accelerating antigen is therefore now done entirely by computer this allows the ECM to modify injector pulse before it actually opens the throttle plates never before has this level of control by the ECM been seen in an automobile before the other reason for drive-by-wire is that the idle speed and cruise control operation is entirely done by computer using the drive by wire electric motor so by using the system’s all the associated components related to the cruise control system and the high a C or idle control valves are eliminated this means a reduction in production costs for the manufacturer as well as higher profits drive-by-wire systems in the vast majority of cases do not employ an IAC valve the idle speed is fully controlled by the electric motor which makes the problem of carbon deposits on the throttle plates much more important and a final point to remember about drive-by-wire systems is that they are totally integrated with the rest of the vehicle module Network for example the ABS system is fully integrated with the throttle control computer in the event of a loss of control of the vehicle by the driver due to wet road or icy road conditions the vehicle will simply throttle down the ECM and effect reduces the torque of the engine and the ABS goes into action to allow the driver to regain control of the car this level of safety is done of course to control the safety of the passengers this level of performance and safety also has a great deal to do with insurance companies pushing for the technology which does work the system is not there to simply increase the complexity or cost of the vehicle in actuality they do lower the general cost of automobiles while give the driver a much higher safety margin now we’ll go into testing the drive-by-wire system in this particular case we see that this system has a motor operated throttle these are the two wires going to the DC motor that drives the throttle plate the way to test the systems is to go in with a scan tool and do our tests using the relevant P IDs you can see the throttle plate in the middle with the motor and the dual TPS at each side this drive-by-wire system is composed of the throttle motor connected to its related gears and clutches which then drives the throttle plate shaft on the other side of the throttle body we see the dual throttle position sensor most of the systems have a dual or triple throttle position sensor as we’ve said before for redundancy this is in case one of the potentiometer fails while the vehicle is being operated in which case you still have one or two potentiometer is left to keep the vehicle running and allow the driver to reach the nearest repair shop in this limpin mode the vehicle will drive with reduced performance and speed these systems are very simple a few key points about the drive-by-wire system is that most of these components have to be reset using the scanner and this is done so that the ECM learns all the particulars about the imperfections of each component after replacement also whenever you do any throttle body cleaning the throttle reset may be needed do not attempt to force open the throttle plate using a screwdriver or your fingers these systems cannot be tampered with due to the fact that if there is any discrepancy between the double TPS at the throttle body and the accelerator pedal position sensor the system will go into a limpin mode with the end result that a drive-by-wire reset may be needed the ACM is constantly checking any discrepancy between the throttle position sensor and the accelerator pedal position sensor if you force the throttle plates open with the screwdriver and you don’t have the proper scan tool to do the resetting you will have to send a vehicle to the dealership to get to reset even to do a throttle body cleaning do not attempt to open the throttle plates by force anytime you do a throttle body cleaning even when done properly replaced the throttle position sensor or the drive-by-wire motor a throttle relearn procedure may have to be performed using a scanner not all vehicles are the same a scan tool may or may not be needed depending on the manufacturer so proper specifications should be consulted again these are simple systems all they require is a little bit of special attention to be paid when working on them here we see on the other side of the throttle body the throttle position sensor which happens to be a dual unit the dual TPS system is simply a double potentiometer throttle position sensor it simply employs a dual wiper system tied to a 5 volts reference and ground line a single or dual carbon trace may be used in some cases some manufacturers will add a second reference voltage and a second ground so that neither of these two values are shared by the internal potentiometers this adds another level of redundancy to the system as we can see on the screen the actual signal is taken from the two legs connected to the potentiometer wipers The Closer that these two wipers get to either of these two values either 5 volts reference or ground is what’s going to determine a final signal output of the sensor unit another curious aspect of this type of TPS is that the signal voltage output at each leg does not swing together in other words as the throttle plates open one signal output could be increasing in voltage while the other decreases to ground so signal one will go from low voltage to high voltage and signal two will go from a high voltage to a low voltage this is normal and again is done this way for redundancy purposes in case one of the output signal lines fail if the ECM starts confusing these two signals as in case of a short circuit it will command the wrong throttle opening there is a possibility that both of these wires short out at the same time causing the output signal to swing together if this happens the ECM will immediately register this condition as a fault and the vehicle will go into limpin mode this throttle position sensor as we can see on screen from the connector has a dual potentiometer type TPS the fastest and easiest way to test the system is by using a scan tool while commanding the throttle plates to open we can also do it manually using a graphing multimeter or oscilloscope later we’ll show you how to do that which is actually very simple as in any other sensor the first step in testing the dual TPS is to start by testing the ground and 5 volts reference line as we can see on screen now next we move our multimeter leap to the ground line of the TPS we can now see on screen the voltage drop between battery or chassis ground and TPS ground remember to use the 100 millivolts rule to test all computer grounds do not stick a screwdriver or your fingers inside the throttle plates have a drive-by-wire system you could very possibly get hurt and end up with broken fingers this is due to the power or torque from the internal gears inside the drive-by-wire motor unit so again we repeat never to stick your fingers inside any electronically activated throttle unit also known as drive-by-wire use the appropriate tools to do the actual cleaning and activating the throttle plates now we’ll test the two outputs from the dual TPS the output value of these two potentiometers is always going to the opposite to each other at this point in time one of the outputs reads one point two four volts then connect the scan tool and select the vehicle we go into vehicle selection to system and into bi-directional control or active command afterwards we go into electronic throttle control and we choose the amount of aperture that we want from the throttle place while at the same time we watch the value on a multimeter we can actually see help by activating the throttle motor using the scan tool and can go through the entire range of effort trauma dual TPS unit this is useful when doing a sweet measurement of both TPS outputs remember use the same rule as when testing a normal TPS unit use extreme caution since some of these blind spots are very hard to detect these blind spots are caused by imperfections and defects in the carbon tracks within the TPS itself however this is not the only way to test the GPS unit on a drive-by-wire system on some systems by simply stepping on the accelerator pedal the system can be made to open and close the throttle plate with Keyon engine off at this point in time we can graph the output of the TPS and test it as you would with a regular throttle position sensor unit by changing the voltage setting we can make the equipment more sensitive to be able to detect a blind spot always look for a smooth voltage sweep trace when doing a drive by wired BPS test by simply freezing the waveform and making an analysis of it we can immediately determine whether we have a good or bad component you do this with a second potentiometer as well remember that the signal is going to be inverted with reference to the other potentiometer within the dual TPS again you can’t freeze the waveform of the signal itself and make the necessary measurements regarding this component using a frozen waveform allows you more time to leisurely determine whether you have a defective component the actual testing of this dual or triple TPS unit is exactly the same as in any other system just keep in mind that the electric motor is the one doing the throttling in the event that your vehicle has a severe lack of performance look into the possibility of a defective accelerator pedal position sensor or throttle position sensor unit the lack of power is a direct result of the ECM reducing performance and allowing the driver to reach the nearest repair shop you simply cannot properly command this type of drive-by-wire system with a defective potentiometer unit within the TPS to summarize the drive-by-wire system it is simply an electric motor connected to a set of gears linked to the throttle blade shaft on the other side as a feedback unit a dual or triple TPS sensor is used this is done for SiC of redundancy in case of a fault you you


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