TPMS stands for Tire Pressure Monitoring System, which was first applied to vehicles exported to North America in accordance with the NHTSA FMVSS 138, and later the application extended to export vehicles bound for Europe. TPMS has been applied on the vehicle as an advanced safety device since the related regulation. According to the frequent accident due to the insufficient tire pressure, it has been necessary to develop more reliable system to monitor the actual pressure and give a proper telltale to the driver while driving.
Textbook Module7 TPMS (Tire Pressure Monitoring System) Module7 TPMS (Tire Pressure Monitoring System) 7.1 O nl y LESSON Overview 177 7.1.1 Introduction 177 7.1.2 Comparison between US and EU Regulation 178 7.1.3 High Line and Low Line 179 Components .181 7.3 Main Components 181 Tire Pressure Sensor (WE Sensor) 182 Receiver 183 Warning Lamp and Position Lamp 184 se 7.2.1 7.2.2 7.2.3 7.2.4 lU 7.2 Control 187 na 7.3.1 Operation Flow Chart and System Block 187 7.3.2 Primary Function (High Line TPMS for North America) 188 7.3.3 Auto Location Logic 191 Sensor Mounting 195 Notes on Tire Handling 197 Replacement Procedure 198 TPMS Exciter 200 Ed 7.4.1 7.4.2 7.4.3 7.4.4 tio TPMS Maintenance 195 uc a 7.4 [Learning Objective] Fo r ▪ Explain the difference between the low line and high line of TPMS ▪ Describe the system layout and list the locations, mechanisms and functions of components ▪ Describe the mechanism of the main functions ▪ Take necessary actions after a part change and list the cautionary measures required for maintenance Basic Chassis Technology 175 Textbook Fo r Ed uc a tio na lU se O nl y Module7 TPMS (Tire Pressure Monitoring System) 176 Basic Chassis Technology Textbook Module7 TPMS (Tire Pressure Monitoring System) Overview 7.1.1 Introduction O nl y 7.1 Figure 7-1 Insufficient Tire Pressure (left) / Alarm on Cluster (right) lU se TPMS stands for Tire Pressure Monitoring System, which was first applied to vehicles exported to North America in accordance with the NHTSA FMVSS 138, and later the application extended to export vehicles bound for Europe na TPMS has been applied on the vehicle as an advanced safety device since the related regulation According to the frequent accident due to the insufficient tire pressure, it has been necessary to develop more reliable system to monitor the actual pressure and give a proper telltale to the driver while driving tio VG F/L has been equipped with a tire pressure monitoring system (TPMS) that illuminates a low tire pressure telltale when one or more of your tires is significantly under-inflated through warning lamp on cluster Accordingly, when the low tire pressure telltale illuminates, you should stop and check your tires as soon as possible, and inflate tires uc a Driving on a significantly under-inflated tire causes the tire to overheat and can lead to tire failure Under-inflation also reduces fuel efficiency and tire tread life, and may affect the vehicle’s handling and stopping ability Ed Please note that the TPMS is not a substitute for proper tire maintenance, and it is the driver’s responsibility to maintain correct tire pressure, even if under-inflation has not reached the level to trigger illumination of the TPMS low tire pressure telltale Fo r TPMS unit can detect system failure by itself Under abnormal condition, cluster lamp blinks for 1min then on When this happen, the system may not be able to detect or signal low tire pressure as intended Basic Chassis Technology 177 Module7 TPMS (Tire Pressure Monitoring System) Comparison between US and EU Regulation O nl y 7.1.2 Textbook lU se Basically, “when warning lamp turns on” is related to the regulation in their region Therefore, before we learn about TPMS basic function, we should understand the regulation In EU / US region, they have different alarm set level since their regulation are not same ‘If the temperature get higher, pressure also get higher.’ This is the basic theory in nature In EU region, they reflect this theory into their regulation Therefore, their alarm set level increase, if the tire get warmer tio na You can check their alarm set level through lower figures PEU means RCP considering temperature compensation logic And PUS means just RCP which is independent value from temperature FYI, RCP means Recommended Cold Pressure (Standard tire pressure in cold state) In EU region, alarm set level is “below 20% from PEU” and it is altered with tire temperature Fo r Ed uc a But US region, they have independent value from temperature which is “below 25% from RCP (PUS).” 178 Basic Chassis Technology Textbook 7.1.3 Module7 TPMS (Tire Pressure Monitoring System) High Line and Low Line lU se O nl y TPMS is mainly categorized as the High-Line and Low-Line The difference between the two types is whether the tire position malfunction lamp turns on or not The High-Line type can indicate to the driver which tire is low in pressure using the tire position malfunction lamp With the Low-Line type, the system indicates that a low pressure has been detected, but the driver does not know which tire it is In order to find which tire has low pressure, High Line system needs auto location function High Line WE Sensor (4EA) tio Zero Initiator (deleted) na Receiver (1EA) Low Line Receiver (1EA) WE Sensor (4EA) Zero Initiator No indicator for the low pressure tire Tire rotation: Auto teaching for Sensor ID Tire rotation : Manual teaching for Sensor ID Fo r Ed uc a Indicator for the low pressure tire Basic Chassis Technology 179 Textbook Fo r Ed uc a tio na lU se O nl y Module7 TPMS (Tire Pressure Monitoring System) 180 Basic Chassis Technology Textbook Module7 TPMS (Tire Pressure Monitoring System) Components 7.2.1 Main Components Fo r Ed uc a tio na lU se O nl y 7.2 Figure 7-2 System Layout Tire Pressure Sensor measures the pressure and temperature of the tires and it sends these data to the Receiver via radio frequency At the same time, the receiver retrieves the vehicle speed from the EMS and the wheel pulse from the ESC (ABS) via CAN communication to determine the location of the tires If a tire reports a problem, that tire is immediately identified and appears in a warning lamp on the cluster The method to identify tires is discussed later in the Auto-Location section Basic Chassis Technology 181 Module7 TPMS (Tire Pressure Monitoring System) 7.2.2 Textbook Tire Pressure Sensor (WE Sensor) O nl y 1) Exploded View of Wheel Sensor and Its Role Figure 7-3 Location (left) / WE Sensor (right) tio na lU se The tire pressure sensor is called ‘WE sensor’ (WE: Wheel Electronic) The tire pressure sensor weighs about 35 g, and is fitted to the rim of each wheel (4 in total), except to that of the spare tire A small cell battery is embedded in the sensor Its battery life is about 10 years The pressure sensor measures the tire pressure, temperature, acceleration, the battery voltage, etc., and sends the data with the sensor ID to the TPMS receiver via RF The measurement frequency and transmission frequency are set differently to extend the battery life in the sensor Each sensor has a unique ID number, so if the sensor is replaced or the tire position has changed, a new ID must to be registered in the Receiver The tire pressure sensor component cannot be checked for faults with a conventional multimeter or wave forms because it is wireless, so a separate wireless diagnostic tool (TMPS exciter) is used to communicate with the sensor to read its ID or check the data measured by the sensor It uses RF (Radio Frequency) signal to transmit to the TPMS receiver, and the emitted frequency is 433 MHz in Euro and General market Mode uc a 2) Mode for Tire Pressure Sensor Ed MP (Parking Mode) Fo r MFB (First Block Mode) MD (Driving Mode) MI (Interim Mode) Description Freq ▪ Keeping no motion status for 15 13 Hours ▪ Mode for parking and A/S part ▪ In MP, if sensor notice a change over 4g, MFB is activated 16 sec ▪ This mode is kept only for about 10min ▪ Mode for Auto Learning / Location In MFB Mode, it keeps moving condition (>4g) for 10min, enter into MD mode ▪ In MD or MFB, if it notice no motion (25kph after minimum 15min Parking), it starts Auto Learning Figure 7-6 Auto Learning Entry Condition = MFB Mode Entry Condition Fo r Specific process of Auto Learning is as follows As soon as each sensor enters into MFB mode ( > 25kph after minimum 15min Parking), it starts Auto Learning If the sensor ID that already saved in Receiver and received sensor ID are same, Auto Learning is completed well (Known ID : single sending) But because of some reasons, like replacing sensor, if two IDs are not same or matching, sensor send ID to Receiver another more times to store new sensor ID (Unknown ID : times sending) Even though it sends ID times, if Auto Learning is not completed, Auto Learning fails and DTC set When replacing sensor, it is very convenient to register new sensor ID into Receiver by Auto Learning because all you have to is just driving 10min over 25kph But if the situation doesn’t allow to driving, you can input new sensor ID by GDS It is quicker way than Auto Learning but you need GDS tool Basic Chassis Technology 189 Module7 TPMS (Tire Pressure Monitoring System) Textbook 4) Auto Location NOTE na lU se O nl y And Auto-Location means that the system locates which tire contains the corresponding pressure sensors from the learning obtained in the Auto-Learning process This is example for Auto Location IDs are randomly assigned uc a tio Entry condition for Auto Location is exactly same as Auto Learning In MFB mode, Auto Location is automatically conducted and takes in 10 minute But if the situation doesn’t allow to driving, you can register new sensor ID by GDS By the way, Understanding process of Auto Location is much more difficult than Auto Learning It use wheel pulse signal to find where each sensors are mounted But this logic is quite complex and not very helpful for TPMS maintenance Ed However, Auto Location logic is described next chapter for someone who wants to know it If you think it won’t be necessary for yourself, you can skip that chapter Fo r 5) Self-Diagnosis Self-Diagnosis means TPMS system can diagnosis by itself If problem about TPMS happens, DTC set automatically All DTC related to TPMS are arranged on last section 190 Basic Chassis Technology Textbook 7.3.3 Module7 TPMS (Tire Pressure Monitoring System) Auto Location Logic O nl y 1) Principle for Auto Location The angular speed of each wheel differs because: se ▪ The slip is different at each shaft ▪ The turning radius (curve radius) of each wheel is different lU ▪ Wear, inner pressure, and tire specifications may be different for each tire Therefore, if FL wheel makes one rotation, it doesn’t mean that the rest of wheel makes exact one rotation Maybe they could make more one rotation or less one rotation tio na Because wheels is not fixed and there are loose mechanical connection among them, they have no correlation But TPMS sensor and individual wheel have grate correlation since they are mechanically fixed strongly uc a In R&D center, researcher experimented on this theory Even on a normal flat road, above theory is identified to be valid Fo r Ed 2) Procedure for Auto Location In MFD mode, the tire pressure sensor sends RF signals every 16 seconds But to be precise, this sending interval is nor exact 16 sec sensor sends signal at every fixed position, having 16 sec interval As shown in up-side figure, RF signals are sent only when the sensor is placed at location N (RF signals are transferred only when the tires report a specific phase) The location N shown here is just an example The actual location may differ Basic Chassis Technology 191 Module7 TPMS (Tire Pressure Monitoring System) Textbook O nl y Whenever Receiver receives RF signals from each sensor, it also receives wheel pulse signal from wheel pulse sensor in order to figure out a degree of each wheel at the moment If the number of teeth in the wheel sensor is 52, the status of each wheel is received as a number where one turn (360°) is equally divided into 104 pieces (52x2) as shown in right side of figure Numbers to 104 are correlated to that wheel's pulse If data differs by 104, then the wheels have the same status lU Ed uc a tio na And Receiver simply receive it from ESC/ABS se Actually this value is calculated by ESC/ABS In order to calculate this value, ESC/ABS makes reference point and count wheel teeth from reference for a period of time Figure 7-7 Receiver Accumulates Wheel Pulse Data for ONE ID In case of this figure → sensor for FL wheel Fo r Assume that FL sensor transmits a single RF signal to Receiver At this moment, Receiver tries to figures out a degree of each wheels by receiving wheel pulse signal And Receiver store these value in memory Until now Receiver couldn’t matching each sensor signal and its corresponding position After 16 sec, when FL sensor come back this fixed position again, it sends sensor ID and Receiver receives RF signal and tries to find a degree of each wheels in the same way a while ago In this time wheel pulse value from FL has a good chance to be similar to previous value in memory because they have grate correlation and they are mechanically fixed strongly 192 Basic Chassis Technology Textbook Module7 TPMS (Tire Pressure Monitoring System) However, because the rest of wheels (FR, RL, RR) make less one rotation or more one rotation and they have no correlation with RL sensor, they might have been different value from previous value Every time an RF signal is received from sensor IDs, the wheel status information from the wheel pulse sensors is collected and stored A relevant ID is allocated to the location with the most consistent measurements In this case, ECU allocate ID to FL position Receiver can find tire locations after 10 times RF reception when the best case uc a tio na lU se O nl y In the opposite case, even after 40 times RF reception, if Receiver can’t decide its location because too many value are same, Auto Location is failed and DTC is set Fo r Ed Figure 7-8 Example for Auto Location Basic Chassis Technology 193 Textbook Fo r Ed uc a tio na lU se O nl y Module7 TPMS (Tire Pressure Monitoring System) 194 Basic Chassis Technology Textbook Module7 TPMS (Tire Pressure Monitoring System) 7.4 TPMS Maintenance 7.4.1 Sensor Mounting 1) Tire Pressure Sensor Installation Procedures O nl y Be sure to check whether the valve (silver air intake) has shifted from its original position during the sensor transportation Then assemble the sensor with the valve inserted into its original position (metal bracket) While the nut is fastened, make sure that the valve will not fall out from the fixed position rotating together; for a successful process, insert the valve into the fixed position (insert into the metal bracket) Fasten the nut with the specified torque (8 Nm); not reuse a used nut se Insert the valve so that the seal washer is in contact with the rim As shown in the pictures below, hold the housing with two fingers and use another finger to guide the valve into the valve shaft direction Figure 7-9 Correct Sensor Mounting Fo r Ed uc a tio na lU The housing laser marking should be seen from above NOTE Figure 7-10 Incorrect Sensor Mounting If you push the front of the pressure sensor in the direction of the rim, the valve will fall out; so care should be taken When the valve is inserted completely, start to fasten the nut manually with the sensor in contact with the rim Basic Chassis Technology 195 Module7 TPMS (Tire Pressure Monitoring System) Textbook While keeping the valve and sensor from moving, finish the installation using a tool After the sensor is mounted, the following requirements should be met: O nl y 2) Inspection Procedures after Tire Pressure Sensor Mounting The seal washer should be pressed against the outside surface of rim hole The valve foot should be located in a specific location of the housing (in the metal bracket) The housing should touch the surface of the rim at at least one point Fo r Ed uc a tio na lU se The housing installation height should not exceed the Rim’s hump height 196 Basic Chassis Technology Textbook 7.4.2 Module7 TPMS (Tire Pressure Monitoring System) Notes on Tire Handling How to prevent the sensor from being damaged while it is dismounted or remounted is described as follows In particular, changing tires is a task for drivers to often, so they need to be more careful when they change tires For more information, see the maintenance manual When dismounting the tire, discharge the air completely from the tire and for the sake of safety attach at some distance from the sensor the tool, if needed, to detach the tire from the bead of the rim O nl y The sensor may be damaged by the tool, if the sensor is located in the forward direction of wheel rotation when the tool is placed on the wheel to detach the tyre Therefore, the tool must be placed where the sensor is in the backward direction of wheel rotation tio na lU se When mounting a tire, positioning the sensor at the o'clock direction as shown in the picture below on the right is the safest way to avoid damaging the sensor Tire Mounting Fo r Ed uc a Tire Dismounting Placing a Guide Basic Chassis Technology Sensor Damaged from Tire Mounting 197 Module7 TPMS (Tire Pressure Monitoring System) 7.4.3 Textbook Replacement Procedure 1) When Replacing Tire Pressure Sensor Fo r Ed uc a tio na lU se O nl y The replaced sensor’s ID should be saved in the receiver The waiting time of 15 minutes with standstill is required for the sensor replacement and thereafter drive the vehicle at over 25km/h for over 10 minutes (actually it’s condition for sensor to enter into MFB) and the ID and position will be automatically saved (it’s Auto Location) In the case when circumstances not allow driving the vehicle on the road, but the new ID needs to be saved urgently, however, the sensor ID can be directly entered by using a TPMS exciter or manual input via GDS 198 Basic Chassis Technology Textbook Module7 TPMS (Tire Pressure Monitoring System) 2) When Replacing TPMS Receiver The A/S part receiver must be changed to normal mode from virgin mode The cluster warning lamp blinks if this mode change is not made TPMS of VG F/L have continental specifications, which changes virgin mode to normal mode automatically while driving; this automatically turns off the warning lamp when a certain speed is reached If a vehicle must be handed over to a customer immediately, register a sensor ID in GDS to change to normal mode Fo r Ed uc a tio na lU se O nl y The manufacturers Mobis and TRW not offer an auto mode change function, so a mode change must be made in GDS Basic Chassis Technology 199 Module7 TPMS (Tire Pressure Monitoring System) TPMS Exciter O nl y 7.4.4 Textbook lU se TPMS exciter is a device developed to conduct various maintenance related tasks by waking pressure sensor Our company has developed and distributed in Korea a TPMS exciter that can be connected to a GDS via cable to perform relevant tasks, and its main functions are described below and next page: 1) Sensor ID Verification tio na Before assembling the wheel the ID can be checked by sight as it is printed on the sensor, but once the wheel is completely assembled the ID can't be checked from outside In this case, the ID of each sensor may be checked via communication between the diagnostic tool and the receiver, but it is necessary to confirm that the receiver's information is 100% accurate Here by bringing the TPMS exciter close to a sensor and sending a wireless command it is possible to confirm the ID of the responding sensor directly (GDS can the job) uc a 2) Individual Sensor Fault Checking Ed Tire pressure sensors not have any external cables as it uses RF for wireless communication Therefore, unlike other sensors, there is no way to check the output (the output before it is sent to the ECU) of the individual sensor However, it is possible to directly determine the sensor's output values by using a TPMS exciter They include pressure, temperature, and battery information, etc Fo r 3) Sensor ID Registration It is possible to register sensor IDs with Auto-Learning and Auto-Location after replacing or changing the TPMS receiver, sensor or tire locations, but using a TMPS exciter allows tasks to be performed more quickly and accurately Follow the instruction from the GDS to position a TPMS exciter near the target tire and press the enter key to save the sensor ID and location of each ID GDS is not limited by location as it can communicate via R/F with the VCI, but as the TPMS exciter must be taken near to the rear right tire the cable connecting the module with the GDS is supplied with a sufficient length 200 Basic Chassis Technology ... O nl y Module7 TPMS (Tire Pressure Monitoring System) 176 Basic Chassis Technology Textbook Module7 TPMS (Tire Pressure Monitoring System) Overview 7. 1.1 Introduction O nl y 7. 1 Figure 7- 1 Insufficient... uc a tio na lU se O nl y Module7 TPMS (Tire Pressure Monitoring System) 180 Basic Chassis Technology Textbook Module7 TPMS (Tire Pressure Monitoring System) Components 7. 2.1 Main Components Fo... Technology 1 87 Module7 TPMS (Tire Pressure Monitoring System) 7. 3.2 Textbook Primary Function (High Line TPMS for North America) Function Description Remark ▪ Warn on = RCP × 75 % + 7kpa = 172 kpa(25psi)