March 2022 - 29

One thing I have personally seen is different brand sensors
ITS600
causing intermittent problems. I have seen some sensors that " go
to sleep " while the vehicle sits overnight and then don't wake up
until the vehicle is at a certain speed. The tire light will be on
when the customer starts the vehicle, but it may go off once up
to driving speeds. If you run into this scenario, make sure the
sensors are learned into their correct positions first. If the sensors
are in the wrong position, like in Figure 2, it can cause you
to chase the wrong sensor.
The left column of Figure 2 shows the actual position while
the right column shows the position the ID is programmed to in
the vehicle data. After this is checked, go for a drive while looking
at live data for the sensors, the one that's not reading pressure
correctly is your culprit. To prevent this from happening I like
to use OE sensors from companies like Schrader, Continental,
and others. If an OE sensor isn't available, then my go to is the
Autel MX-1 TPMS sensors. These sensors combine 315 MHz
and 433 MHz into one sensor and have only one SKU for easy
inventory. There is nothing wrong with other aftermarket sensor
options as well, but I have personally encountered problems that
were caused by aftermarket sensors that were the incorrect part
number for the application. The sensor was not faulty but was
incorrect for the vehicle. When a supplier has many different part
numbers, this is more likely to happen when the part numbers
are entered into inventory at a parts store. That's why I prefer
OE or Autel's simple one sensor approach.
INDIRECT TPMS
Now, let's look at indirect TPMS. Early systems looked at the
difference in wheel speed via the ABS sensors to determine
when a tire was low. As the tire loses air the circumference
becomes smaller resulting in the wheel speed increasing. When
that is recognized by the ABS module, a low tire light is displayed.
The problem these systems had was they could only
tell if one, two, or three tires were low, but they couldn't tell if
all four were low. This is because if all four tires gradually lost
air, then they would all be the same circumference. Luckily for
us, the indirect TPMS being used on new vehicles is substantially
different from the earlier versions. Now, the system is
integrated into the VSA modulator-control unit and uses the
following inputs to monitor and compare tire characteristics
to determine when one or more tires are significantly underinflated;
VSA/ABS wheel speed sensors, Yaw and G sensor, brake
pressure, steering angle, and outside temperature (measured
from the front bumper) are all used.
From these inputs, the system calculates tire pressures.
To determine tire pressure loss, the system uses these two
methods: wheel speed differential and peak tire resonance.
Wheel speed differential is calculated by performing a diagonal
comparison between the front and rear wheels, a comparison
between the two front and two rear wheels, and a comparison
between the two right and two left wheels.
ON T O OL
DIG I TA L T IRE
REGISTRATION
1. Select " TIRE REGISTRATION " on
the ITS600 Main Screen
2. Select the Tire Manufacturer
3. Type in the DOT Number in Correct
Format and the Quantity
4. Tap " SUBMIT " and You're All Set!
AVOID NON COMPLIANCE FINES BY USING DIGITAL
CIMS TIRE REGISTRATION ON THE ITS600!
PLUS:
* PERFORM TPMS DIAGNOSTICS
* SENSOR PROGRAMMING
* VEHICLE RELEARNS
END
THE
PAPERCHASE
DIGITAL TIRE REGISTRATION - DOT COMPLIANT
TEL: (855) 288-3587 * USSUPPORT@AUTEL.COM
AUTEL.COM * MAXITPMS.COM * MAXISYSADAS.COM
©2022 AUTEL U.S. INC., ALL RIGHTS RESERVED
www.VehicleServicePros.com MARCH 2022 PROFESSIONAL TOOL & EQUIPMENT NEWS
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29
2/10/22 3:18 PM
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March 2022

Table of Contents for the Digital Edition of March 2022
