Module 7 TPMS (tire pressure monitoring system) eng

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.

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Monitoring System)

LESSON

7.1 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

7.2 Components 181

7.2.1 Main Components 181

7.2.2 Tire Pressure Sensor (WE Sensor) 182

7.2.3 Receiver 183

7.2.4 Warning Lamp and Position Lamp 184

7.3 Control 187

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

7.4 TPMS Maintenance 195

7.4.1 Sensor Mounting 195

7.4.2 Notes on Tire Handling 197

7.4.3 Replacement Procedure 198

7.4.4 TPMS Exciter 200

[Learning Objective]

▪ 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

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Figure 7-1 Insufficient Tire Pressure (left) / Alarm on Cluster (right)

TPMS stands for Tire Pressure Monitoring System, which was first applied to vehicles exported to NorthAmerica in accordance with the NHTSA FMVSS 138, and later the application extended to export vehiclesbound 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 developmore reliable system to monitor the actual pressure and give a proper telltale to the driver while driving

VG F/L has been equipped with a tire pressure monitoring system (TPMS) that illuminates a low tirepressure telltale when one or more of your tires is significantly under-inflated through warning lamp oncluster Accordingly, when the low tire pressure telltale illuminates, you should stop and check your tires

as soon as possible, and inflate tires

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 andstopping ability

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 ofthe TPMS low tire pressure telltale

TPMS unit can detect system failure by itself Under abnormal condition, cluster lamp blinks for 1min thenon

When this happen, the system may not be able to detect or signal low tire pressure as intended

‘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.You can check their alarm set level through lower figures PEU means RCP considering temperaturecompensation logic And PUS means just RCP which is independent value from temperature FYI, RCPmeans 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

But US region, they have independent value from temperature which is “below 25% from RCP (PUS).”

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7.1.3 High Line and Low Line

TPMS is mainly categorized as the High-Line and Low-Line The difference between the two types iswhether the tire position malfunction lamp turns on or not The High-Line type can indicate to the driverwhich tire is low in pressure using the tire position malfunction lamp With the Low-Line type, the systemindicates that a low pressure has been detected, but the driver does not know which tire it is In order tofind which tire has low pressure, High Line system needs auto location function

High Line Low Line

Receiver (1EA)

WE Sensor (4EA)Zero Initiator (deleted)Indicator for the low pressure tireTire rotation: Auto teaching for Sensor ID

Receiver (1EA)

WE Sensor (4EA)Zero Initiator

No indicator for the low pressure tireTire rotation : Manual teaching for Sensor ID

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Figure 7-2 System Layout

Tire Pressure Sensor measures the pressure and temperature of the tires and it sends these data to theReceiver via radio frequency At the same time, the receiver retrieves the vehicle speed from the EMS andthe 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

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7.2.2 Tire Pressure Sensor (WE Sensor)

1) Exploded View of Wheel Sensor and Its Role

Figure 7-3 Location (left) / WE Sensor (right)

The tire pressure sensor is called ‘WE sensor’ (WE: Wheel Electronic) The tire pressure sensor weighsabout 35 g, and is fitted to the rim of each wheel (4 in total), except to that of the spare tire A small cellbattery is embedded in the sensor Its battery life is about 10 years The pressure sensor measures thetire 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 pressuresensor 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

2) Mode for Tire Pressure Sensor

Mode Description Freq.

MP (Parking Mode) ▪ Keeping no motion status for 15 min.

MFB (First Block Mode)

▪ In MP, if sensor notice a change over 4g, MFB is activated

▪ This mode is kept only for about 10min

▪ Mode for Auto Learning / Location

16 sec

MD (Driving Mode) In MFB Mode, it keeps moving condition (>4g) for 10min,

1) Exploded View of Receiver and Its Role

Figure 7-4 Mounting Location: Cowl Crossbar inside the Crash Pad

Receiver receives RF signals (315MHz) from the tire pressure sensors and then analyzes data it alsoreceives vehicle speed signal and wheel pulse signal from EMS, ESC(ABS) at the same time

The reason Receiver get the signal from EMS, ESC(ABS) is for preforming Auto Learning and AutoLocation And it controls Warning lamp on cluster

2) Receiver Mode

Mode System Lamp Status Remark

▪ Mode for factory Line

Blinking

▪ A Sensor ID is not registered

▪ Mode for A/S part

▪ Normal operating status

TIP

Depending on the manufacturer, three or four initiators are installed on a single high-line TPMS forsensor location detection Manufacturers are opting to not install initiators as sensor locations can

be detected using pressure sensor signal intensity and the acceleration sensor inside the sensors,

as well as for cost-reduction reasons

Initiators perform the following functions when installed

▪ Emits LF signal to the sensor

▪ Wake-Up the sensor

▪ Tire position detection

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7.2.4 Warning Lamp and Position Lamp

1) Warning Lamp for Low Pressure

Normal Operation Wrong Operation Normal Mode (Start

A sensor ID isn’t stored, the warning lamp keeps blinking

3 Low pressure lamp

When the tire pressure is lower than a specified value, the warning lamp turned on Usually, it is turned

on when the pressure drops lower than 26 - 27psi And when the pressure is over 30, 31psi, it is turnedoff

Figure 7-5 Tire Pressure

4 Malfunction lamp

When the system is in failure, the lamp blinks for 60 seconds

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▪ Warn on = RCP × 75% + 7kpa = 172kpa(25psi)

▪ Warn off = RCP - 14kpa = 207kpa(30psi)

* VG F/L RCP: 221kpa(32psi)

▪ Based on ALL Genuine Part(17,18,19 inches)

Margin exists forhysteresis (+7, -14kpa)

Tire Fast Leak

Detection Sensing a rapid air leak over 20kPa/min (3psi/min)

Only Activating in driving(To avoid activating adriver deflate a tire onpurpose)

Auto Learnin

▪ VS over 25kph / 1 RF Frame (Known ID)

▪ VS over 25kph / 8 RF Frame (Unknown ID)

(MAX 40 times, MIN 10 times)

Failure condition: 40times (40*16=660sec)

Self-Diagnosi Turning on warning lamp via system diagnosis DTC

1) Under-inflation Detection

The most basic function of the TPMS is turning warning lamps on when tire pressure drops Specificcondition is refer to upper table

2) Tire Fast Leak Detection

If pressure sensor detects a pressure change of 6.8 kpa/min or more, it automatically sends this data TheReceiver calculates a leak rate limit (usually 20 kPa/min = 3psi/min) and send warning messages even iftire pressure cannot reach the warn off condition

This feature only functions while driving in order to avoid warnings when the driver deflates the tire pressure

on purpose in parking

3) Auto Learning

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NOTE This is example for Auto Learning IDs are randomly assigned

Specific process of Auto Learning is as follows

As soon as each sensor enters into MFB mode (>25kph after minimum 15min Parking), it starts AutoLearning

Figure 7-6 Auto Learning Entry Condition = MFB Mode Entry Condition

Specific process of Auto Learning is as follows

As soon as each sensor enters into MFB mode ( > 25kph after minimum 15min Parking), it starts AutoLearning

If the sensor ID that already saved in Receiver and received sensor ID are same, Auto Learning iscompleted 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 7 more times to store new sensor ID (Unknown ID : 8 times sending)

Even though it sends ID 8 times, if Auto Learning is not completed, Auto Learning fails and DTC set

NOTE This is example for Auto Location IDs are randomly assigned.

Entry condition for Auto Location is exactly same as Auto Learning In MFB mode, Auto Location isautomatically conducted and takes in 10 minute But if the situation doesn’t allow to driving, you canregister new sensor ID by GDS

By the way, Understanding process of Auto Location is much more difficult than Auto Learning It usewheel pulse signal to find where each sensors are mounted But this logic is quite complex and not veryhelpful for TPMS maintenance

However, Auto Location logic is described next chapter for someone who wants to know it If you think itwon’t be necessary for yourself, you can skip that chapter

5) Self-Diagnosis

Self-Diagnosis means TPMS system can diagnosis by itself If problem about TPMS happens, DTC setautomatically All DTC related to TPMS are arranged on last section

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7.3.3 Auto Location Logic

1) Principle for Auto Location

The angular speed of each wheel differs because:

▪ The slip is different at each shaft.

▪ The turning radius (curve radius) of each wheel is different.

▪ 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

Because 4 wheels is not fixed and there are loose mechanical connection among them, they have nocorrelation But TPMS sensor and individual wheel have grate correlation since they are mechanicallyfixed strongly

In R&D center, researcher experimented on this theory Even on a normal flat road, above theory isidentified to be valid

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 signalsare transferred only when the tires report a specific phase)

The location N shown here is just an example The actual location may differ

And Receiver simply receive it from ESC/ABS.

Figure 7-7 Receiver Accumulates 4 Wheel Pulse Data for ONE ID

In case of this figure → sensor for FL wheel

Assume that FL sensor transmits a single RF signal to Receiver At this moment, Receiver tries to figuresout a degree of each 4 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 4 wheels in the same way a while ago In this time wheel pulsevalue from FL has a good chance to be similar to previous value in memory because they have grate

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

In the opposite case, even after 40 times RF reception, if Receiver can’t decide its location because toomany value are same, Auto Location is failed and DTC is set

Figure 7-8 Example for Auto Location

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1) Tire Pressure Sensor Installation Procedures

1 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)

2 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 metalbracket) Fasten the nut with the specified torque (8 Nm); do not reuse a used nut

3 Insert the valve so that the seal washer is in contact with the rim.

4 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

5 The housing laser marking should be seen from above.

Figure 7-9 Correct Sensor Mounting

Figure 7-10 Incorrect Sensor Mounting

NOTE 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

6 When the valve is inserted completely, start to fasten the nut manually with the sensor in contact

with the rim

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7 While keeping the valve and sensor from moving, finish the installation using a tool.

2) Inspection Procedures after Tire Pressure Sensor Mounting

After the sensor is mounted, the following requirements should be met:

1 The seal washer should be pressed against the outside surface of rim hole.

2 The valve foot should be located in a specific location of the housing (in the metal bracket).

3 The housing should touch the surface of the rim at at least one point.

4 The housing installation height should not exceed the Rim’s hump height.