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
AC current output
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
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]
The sensors are powered by a built in battery

15. Tire pressure sensor
Stem seal
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.

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. 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.
Receiver
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. Hexadecimal ID number [last 7 digits]
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
# 05D1264
# 0EA4497
# 0EA4492
# 05D1267
# 1BA3842
# 1BA3847
# 0EA4486
# 0EA4495
# 05D1265
# 05D1268
# 1BA3846
# 1BA3844
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

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
# 1BA3844
# 1BA3846

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 sequence1 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. Magnetic TPMS sensor trigger
Some manufacturers use a magnet to trigger the TPMS sensor into ‘wake up’ mode
When a doughnut shaped magnet is placed over the TPMS stem the sensor broadcasts it’s data to the TPMS module

32. Using the TPMS3

33. 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

34. 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

35. 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

36. 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

37. 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

38. 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

39. 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

40. 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

41. 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

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

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

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

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

46. 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

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

48. 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]

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

50. 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

51. 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

52. Test drive the vehicle
After the relearn procedure the TPMS indicator light will be illuminated
The vehicle must be driven a short distance to allow the pressure sensors to broadcast data
After the TPMS module sees a signal from each sensor the TPMS light will turn off.

53. Replacement sensor part #database
Identify Vehicle Make, Model, Model Year, # of wheels
The TPMS3 has an application and part number database of after-market sensors
Use the up/down arrows to see different vendors
The database can be used to determine if the installed sensor is the proper sensor for the vehicle

54. Troubleshooter
The troubleshooter uses diagnostic trees and the built in knowledge base to help determine the cause of an illuminated or flashing TPMS warning light

55. Radio Frequency [RF] signal strength testing
The TPMS3 can also be used to test the strength of the radio frequency emitted by the key fob and vehicle security/remote lock system

56. RF signal strength testing
Input the make, model and model year to set the TPMS to monitor the correct frequency for the system
If the system uses more than one frequency you may have to select the frequency from a menu list

57. Key Fob test
Hold the TPMS3 close to the key fob then press the lock button on the fob
The signal strength bar graph should move to the right when the button is depressed
Repeat the test for the unlock and panic buttons

58. Other RF signal strength testing
Bi-directional RF communication between the vehicle’s security system and the key fob can be tested using the RF signal strength meter
Move the TPMS3 close to the drivers door and observe the strength meter bar graph
The down arrow above the bar graph indicates the maximum strength measured during the test

59. Code reader
The OBDII interface can be used to read Diagnostic trouble codes
The TPMS3 will not display serial data and does not identify the meaning of the DTC
The Modus or Verus are better tools for diagnosing OBDII system problems

60. Docking station
To charge the battery the TPMS must be installed on the docking station and connected to the power supply
The USB port on the side of the docking station allows the TPMS3 sensor database to be updated
Update information is download from the internet into the PC then transferred via the USB cable to the TPMS3
Power adapter plug