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Tire pressure
monitoring
systems
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
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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
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ABS wheel speed sensor
AC current
output
Induction coil
Magnet
• 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
• Continuous rotation of the tone ring
produces an AC current whose
frequency – measured in Hertz – is
proportional to wheel speed
Tone ring
Indirect TPM systems
RF
802 Hz +2
LF
798 Hz -2
RR
801 Hz +1
LR
779 Hz -1
800 Hz Avg.
• 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
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Indirect TPM systems
RF
812 Hz +12
LF
798 Hz -2
RR
801 Hz +1
LR
779 Hz -1
800 Hz Avg.
• 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
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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
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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
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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
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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
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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.
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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
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
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Direct TPM systems
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• 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
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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.
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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
• Ideally the receiver is located 17
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
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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
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Sensor ID
Rubber
seal]
Hexadecimal ID
number [last 7 digits]
• 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
Sensor ID number
• 7 digit hexadecimal ID number
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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
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
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ID# registration
# 0EA4497
# 0EA4492
# 1BA3842
# 0EA4486
# 0EA4495
# 1BA3844
# 05D1267
# 05D1264
# 1BA3847
# 05D1265
# 05D1268
# 1BA3846
• 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
Registration [relearn]
# 1BA3842
# 1BA3847
# 1BA3844
# 1BA3846
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• 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
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
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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
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
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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
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TPM registration sequence
1
2
4
3
• 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
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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
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Using the
TPMS3
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
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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
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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
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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
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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
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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
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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
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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
Move to the right front wheel
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• 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
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Move to the right rear wheel
• The position indicator
on the screen will
indicate the sensor
being tested
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Move to the left rear wheel
• If the spare tire
does not have a
sensor the test
sequence will end
at the left rear
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Sensor data display
Pressure
Frequency
Sensor ID #
Status
Temperature
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Sensor ID #
• Note that the ID # on the sensor is the same as
displayed on the TPMS3 screen
Printing sensor data report
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• 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
Sensor data review
• Sensor data is held in memory and can be reviewed
through the ‘Print’ menu
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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]
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
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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
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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
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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.
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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
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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
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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
• 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
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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
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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
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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
Docking station
• The USB port on the
side of the docking
station allows the
TPMS3 sensor database
to be updated
• To charge the battery the TPMS
must be installed on the docking
station and connected to the power
supply
• Update
information is
download from the
internet into the PC
then transferred via
the USB cable to
the TPMS3
Power adapter plug
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