Tire pressure monitoring systems

1. Tire pressure monitoring systems

2. Tire pressure monitoring systems • Direct tire pressure monitoring systems are required on all cars and light trucks sold in the United States after Sept 1, 2007 • In the 1990s low tire pressure in was identified as a primary factor in hundreds of fatal SUV rollover accidents • Some studies have indicated that close to 10% of all highway fatalities can be linked to low tire pressure • Tire pressure monitoring system were originally developed in the 1980s for use with run-flat tires

3. Tire pressure monitoring systems • There are two types of TPM systems: • Indirect – uses ABS speed sensors to detect a loss of pressure • Direct – uses air pressure sensors inside the wheel to detect true tire pressure

4. ABS wheel speed sensor • The ABS wheel speed sensor generates a small electrical pulse whenever a tooth on the tone ring moves through the magnetic field of the pick up coil AC current output Induction coil Magnet • Continuous rotation of the tone ring produces an AC current whose frequency – measured in Hertz – is proportional to wheel speed Tone ring

5. Indirect TPM systems • Indirect tire pressure monitoring systems use the ABS system’s wheel speed sensors to detect sudden changes in wheel speed variation • The system monitors the difference in frequency between the ABS sensors continuously updating the sensor variation table in the TPMS system’s memory chip • In the illustration here the Right Front sensor outputs a frequency that is consistently 2% higher than the average RF 802 Hz +2 LF 798 Hz -2 RR 801 Hz +1 LR 779 Hz -1 800 Hz Avg.

6. Indirect TPM systems • As the tires wear the system recalculates the variation in speed for each sensor • If there is a puncture the pressure inside a tire is reduced and the overall diameter of the tire becomes slightly smaller • As a result the speed of the wheel increases slightly • This sudden increase in speed variation triggers the system to turn on the ‘Tire’ pressure warning light and sets a chassis code RF 812 Hz +12 LF 798 Hz -2 RR 801 Hz +1 LR 779 Hz -1 800 Hz Avg.

7. Indirect TPM system reset • Whenever new tires are installed or tires are rotated the TPMS system needs to recalculate the sensor variation table • Each manufacture has its own procedure • The most common is a reset button in the fuse box • With the ignition key on the TPMS reset button is depressed for 5 seconds or until the TPMS warning light goes out • After the TPMS reset it takes 40 to 60 minutes of driving for the system to recalibrate

8. Direct TPMS system requirements • Vehicles sold in the USA after 9/1/2007 are required to have a direct TPMS system with the following features: • Monitoring of tire pressure in all four tires. Monitoring the spare is not required • A TPMS system that operates when the vehicle ignition is on and warns when tires are underinflated by -25% or more • A TPMS system that alerts the driver when there is a system malfunction

9. Direct TPMS system requirements • A TPMS warning light that stays on until the tire is inflated to the proper pressure or the system malfunction is corrected • A "bulb check" of the warning light on the instrument panel that occurs whenever the ignition is turned on • Vehicle owner's manuals that contain warnings about potentially incompatible replacement tires or wheels for the vehicle • Vehicles with dual wheels on one axle are exempt • By law the TPMS system cannot be bypassed or deactivated

10. ISO standard warning indicator • All vehicles must use the ISO standard warning indicator to alert the driver of a low pressure tire • When the TPM indicator light is on the message center in the instrument cluster should describe which tire is low

11. Flashing TPM warning light • If the TPM warning light flashes on and off at 3 second intervals it indicates a failure in the TPM system • Generally this is because the system cannot ‘see’ one or more sensors • This can be the result of a damaged sensor or a dead sensor battery • When the TPM warning light is on continuously it indicates a tire with low pressure.

12. Clearing the TPM warning • The TPM warning light will automatically clear after restoring tire pressure and driving the vehicle at 25 mph or faster for 2 minutes • If the spare tire is installed and that tire does not have a pressure sensor the warning light will be illuminated – this provides a prompt to have the regular tire fixed and return the spare to the trunk

13. Inflation mode • Many manufactures have added inflation mode software to their vehicles • When the inflation mode is selected and the vehicle is turned on and in Park the security system beeper will beep when the tire pressure is exact • This allows the driver to inflate the tires until the system beeps – then he can go to the next tire and inflate until it beeps… and so on

14. Direct TPM systems • The sensors are powered by a built in battery • Direct TPM systems have a pressure sensor / transmitter located inside the wheel • The sensor incorporates the valve stem and is retained to the wheel by the valve stem nut • The sensors transmit pressure, and often temperature information to a receiver that is link via the CAN network to the ICM [Instrument Control Module]

15. Tire pressure sensor • The tire pressure sensors are mounted on the rim and retained by a nut on the valve stem. • A rubber gasket seals the pressure sensor to the rim. Stem seal

16. Direct TPM systems • To extend the life of the battery the transmitter turns off when the wheel is not rolling • The battery should last the life of the tire or about 10 years • New sensors cost about $35 –to- $85 • The valve stem can be replaced separately for $5 –to- $10 • Never use a metal [brass or steel] valve cap on a TPM valve stem. The dissimilar metals in the valve core can cause galvanic corrosion that can damage the TPM sensor

17. Receiver • Ideally the receiver is located near the center of the vehicle. • Some manufactures integrate the TPMS receiver function with the remote control door lock receiver. • The receiver communicates with the other modules in the vehicle via the CAN network. TPM receiver

18. Data transmission • An internal accelerometer in the TPMS sensors detects when the tire is rolling • The sensors measure pressure every 30 seconds but transmits only when the tire is rolling • When the tire is rolling the sensor measures pressure ever 30 seconds and transmits every 60 seconds • If tire pressure changes by more than 1.2 psi it will transmit regardless of whether it is rolling or stationary Image courtesy of Robert Bosch GMBH

19. Sensor ID • Each sensor has a unique ID number that is transmitted with the pressure and temperature data • The ID number allows the vehicle to discriminate between tire sensors from nearby vehicles and the sensor s on wheels installed on the vehicle • The ID number also allows the vehicle to identify which corner of the car the tire data is coming from Rubber seal] Hexadecimal ID number [last 7 digits]

20. Sensor ID number • 7 digit hexadecimal ID number

21. Smart vs. Dumb TPMS systems • ‘Dumb’ TPMS systems do not indicate which tire[s] has low pressure when the TPMS warning light is illuminated. This eliminates the need to re-register the sensors each time the tires are rotated • ‘Smart’ TPMS systems will display the location of the tire when the TPMS system receives a low pressure signal from a sensor. This requires that the sensors be re-registered each time the tires are rotated. • In a dumb system the TPMS module knows the ID # for all the sensors but it does not keep track of where each sensor is currently located

22. Sensor initialization procedure • A sensor ID registration procedure is done after tires are rotated or after tire size has changed • The registration procedure should be done in an area away from any other cars in the shop so that the ID signals for another vehicle are not picked up by mistake • Procedures vary between manufactures but the procedure should not require any specialized equipment as it is a normal service routine

23. ID# registration • The registration process insures that the TPMS system only monitors those sensors that belong to the vehicle • Signals from sensors on nearby vehicles that are not registered to the vehicle are ignored # 05D1264 # 05D1267 # 0EA4492 # 0EA4497 # 1BA3842 # 1BA3847 # 05D1265 # 0EA4486 # 0EA4495 # 05D1268 # 1BA3846 # 1BA3844

24. Registration [relearn] • The registration process will record the ID numbers of all the vehicles sensors • It is important that this procedure be done away from other vehicles do that the ID #s of nearby vehicles are not recorded by mistake • Registration must be done when new sensor are installed and when the tires are rotated on vehicles with ‘smart’ TPMS systems # 1BA3842 # 1BA3847 # 1BA3846 # 1BA3844

25. Sensor initialization procedure • The tire pressure must be set to specifications prior to initialization • The tire pressures reported to the TPMS module during the initialization process will be the baseline pressure used by the TPM system in determining when to turn on the TPM warning light • If the specified pressure is 28 psi the warning light should turn on when pressure drops below 21 psi. [75% of 28 psi] • If the TPM system is initialized with a tire at 24 psi the warning light will not illuminate until pressure drops below 18 psi

26. TPMS reset switch • A TPMS reset is normally performed on ‘Dumb’ TPMS system after tire rotation • TPMS reset procedures vary between manufactures • This vehicle has a reset switch located next to the OBDII connector • In this system the switch is depressed for about 5 seconds until the TPMS warning light flashes 3 times OBDII Connector

27. TPM Sensor registration procedure • A TPMS registration [relearn] procedure must be done when a sensor has been replaced • If the owner has a spare set of rims with snow tire installed a registration procedure will be required each time the wheels are exchanged • Procedures vary between manufactures but most manufactures will use a scan tool to set the TPMS module into registration mode • Manufactures also provide alternative methods of setting the TPM system into registration mode that do not require a scan tool or RF [radio frequency] diagnostic tool

28. Sensor registration [learn] activation trigger • The sensors must be triggered to send a learn mode signal during the registration process • The sensors are normally triggered by a radio frequency [RF] signal from a special TPMS tool • These special tools transmit and receive on the same radio frequency as the TPM sensor and are used to diagnose TPM system problems • Some sensors can be triggered to transmit in learn mode by bleeding off a few psi of air pressure

29. TPM registration sequence 1 2 • Sensor registration must be done in a specific sequence • The sequence starts at the left front [drivers side] wheel and continues clockwise around the vehicle • If the vehicle has a sensor in the spare tire that tire is done last 4 3

30. Finding TPM procedures in AllData • The TPMS registration [relearn] procedure is published in AllData • You can get direct access to the TPMS system procedures through the ‘Technician’s Reference’ tab • You can identify the vehicle and then follow the menus to instrument panel, gauges and warning indicators / Tire monitoring system

31. Using the TPMS3

32. TPMS3 functions • The TPMS3 is a radio frequency transceiver [receives and transmits] that can easily determine if the tire pressure sensor is working properly • The TPMS can also connect to the vehicle’s TPMS module via the OBDII connector • Sensor ID and position can be uploaded to the TPMS module via the OBDII interface on Asian vehicles

33. TPMS main menu • Under the TPMS3 main menu you can: • Test the response of all sensors • Reset pressure sensor position data after tire rotation • Relearn pressure sensor ID# after pressure sensor replacement • Troubleshoot illuminated TPMS warning light • Find the correct replacement sensor part number • Test key fob and vehicle’s lock/security transmitter

34. Sensor wake up call • The TPMS3 sends a wake up call to the sensor • Normally the sensor is in sleep mode when the tire is not rotating • When the sensors is in ‘wake’ mode it reads tire pressure and temperature every 30 seconds and transmits it’s data to the TPMS module every 60 seconds

35. Identify the vehicle make, model and year • Select ‘Test Sensor /Pressure from the main menu • Select manufacturer from the ‘Vehicle Selection’ menu • Select model • Select model year

36. Does the spare tire have a sensor • In general if the vehicle has a full size spare tire the spare tire will have a pressure sensor. Vehicles equipped with temporary tires [space saver tires] generally do not have a pressure sensor • After selecting 4 or 5 wheels the TPMS is ready to begin testing

37. Begin testing on the left front wheel • The sensor antenna is in the valve stem so hold the TPMS a few inches away from the stem and press the ‘Test’ button

38. Band type sensor [Ford] Sensor Location • Many Ford vehicles use band type sensors that are not connected to the valve stem and are located 180 degrees away from the stem

39. Receiving pressure data • It may take 30 seconds or more for the tester to wake up and make a handshake with the sensor • If no data is displayed after 1 minute recheck the setup for make, model and year

40. Move to the right front wheel • Sensors are always tested starting at the right front wheel and moving in a clockwise direction • After receiving and displaying data from a sensor press the ‘Y’ key – the TPMS3 will prompt you as to what wheel to test next

41. Move to the right rear wheel • The position indicator on the screen will indicate the sensor being tested

42. Move to the left rear wheel • If the spare tire does not have a sensor the test sequence will end at the left rear

43. Sensor data display Pressure Sensor ID # Temperature Frequency Status

44. Sensor ID # • Note that the ID # on the sensor is the same as displayed on the TPMS3 screen

45. Printing sensor data report • A printout of sensor data can be made by connecting a PC to the USB port on the side of the docking station/charger • Printing is done through the TPMS3 software application USB port

46. Sensor data review • Sensor data is held in memory and can be reviewed through the ‘Print’ menu

47. Connecting to the OBDII port • The TPMS can upload sensor ID and location data to the TPMS module via the vehicle’s OBDII interface [Asian vehicles only] • Locate the OBDII connector – normally under the steering column - and connect the adapter to the TPMS3 using the RJ-45 cable [standard network cable]

48. Reset/relearn procedure [Asian vehicles] • When new sensors are installed the system must relearn the ID # and position of each sensor Identify Vehicle Make, Model, Model Year, # of wheels

49. Record sensor data • Record sensor data from each wheel starting with the left front and proceeding in a clockwise direction • The OBDII connector cable can be disconnected during the data recording and then reconnected before transferring to the TPMS module

50. Transferring data to the TPMS module • Once all of the sensor data has been captured by the TPMS3 it is uploaded to the TPMS module through the OBDII link