Tech Stuff

Dealing with TPMS Problems: Tips to Avoid Issues and Diagnose Glitches

Prior to any TPMS service, existing sensors should be scanned for potential concerns. This step will save your shop a lot of time and aggravation. Photo courtesy of 31 Inc.
<p>Prior to any TPMS service, existing sensors should be scanned for potential concerns. This step will save your shop a lot of time and aggravation. Photo courtesy of 31 Inc.</p>

Rather than covering programming and relearn procedures, a subject that has been addressed in select previous issues, this article focuses on common (and uncommon) concerns that a technician may encounter, along with tips to avoid mistakes. Here, we’ve enlisted the expert advice from some of the leading tire pressure monitoring system (TPMS) sensor and tool makers.

Before starting service, always follow Rule #1 – ask the customer when the TPMS light first came on, and then proceed from there.

The following was provided by Bartec USA’s CEO Scot Holloway:

Technicians can save themselves so much aggravation if they would simply check the sensors with an activation tool before they begin work. It’s even better if they can test the sensors and connect to the OBD and check for TPMS-related DTCs. Not only does this easy first step go a long way in protecting them from inheriting a bad situation, but it’s also a great way to begin a TPMS conversation with the customer.

Many vehicles do not immediately warn the driver of a failed sensor or failed battery. There is no provision for this in TPMS legislation. The TPMS must notify of a low pressure condition immediately. However, the rules on declaring a system fault warning are less rigid. It is increasingly possible and likely for vehicles to arrive at the shop with a dead TPMS sensor, but no warning of it on the instrument panel.

Unfortunately, technicians too often fail to inspect and test the sensors. Depending on the work performed, they will often end up “owning” a dead sensor. The classic example of this is when the TPMS light comes on after a simple tire rotation. Typically, the customer calls shortly after leaving the shop, complaining of a flashing TPMS light. Of course, the technician’s response is, “All I did was rotate the tires and didn’t even touch your sensors!”

The technician is correct: Simply rotating the position of the sensor will not cause a sensor to fail. The sensor was already dead when the customer showed up. The problem is convincing the customer of that fact. Since some technicians oftentimes do not understand TPMS functionality all that well, that conversation doesn’t go very well, and they often end up replacing the sensor at their cost. Instead of discovering the faulty sensor in the beginning, offering to replace the sensor and keep the TPMS operative and make a sale, they are now eating the cost of a new sensor simply to keep the customer happy. The point we’re making is to “Test Before You Touch.” You’ll save time, aggravation and avoidable expense out of the shop’s own pocket.

Another common step often overlooked is the adjustment of recommended inflation pressure or placard. The TPMS works on the basis of the recommended inflation pressure of the tires (given the size, type and load carrying capacity for the vehicle). The low pressure warning light illuminates when one or more of the tire pressures falls below 75% of the recommended inflation pressure threshold.

When plus-sizing or “up-fitting” a vehicle, it is common for the recommended inflation pressure to change. The change can be large enough that the TPMS will no longer function properly.

As a case in point, consider a 2008 Suburban that is fitted with a P-rated tire. If the customer wants the look and performance of the equivalent-sized light truck tire, the recommended inflation pressure goes from 35 psi to 55 psi. This presents a couple of issues.

First, the LT tire would be half deflated before the low pressure warning would illuminate. Secondly, on vehicles that monitor over-pressurization (like GM), the light would be on constantly, making low pressure warning impossible. Therefore, it’s a critical step when plus-sizing or up-fitting that you have a TPMS scan tool that can perform this type of settings change.

When performing a relearn, always keep other tire pressure monitoring system sensors and other TPMS-equipped vehicles a safe distance away from the vehicle’s sensors being relearned. Photo courtesy of VDO Continental TPMS.
<p>When performing a relearn, always keep other tire pressure monitoring system sensors and other TPMS-equipped vehicles a safe distance away from the vehicle&rsquo;s sensors being relearned. Photo courtesy of VDO Continental TPMS.</p>

The following tips were provided by John Rice, director of TPMS products and support, of 31 Inc.:

Program sensors before installing them. This would apply to universal programmable sensors and selectable programmable sensors.

Many Audi, VW, Mazda and Honda vehicles feature indirect TPMS. Vehicles equipped with indirect TPMS do not have sensors in the wheels. Therefore, no sensor will be detected when trying to scan/activate/wake-up the sensors. Typically, the only service required is to inflate the tires to proper pressure and reset by pressing a reset button.

Not all vehicles relearn the TPMS system by simply driving the vehicle after servicing the TPMS. Actually, only about one-third of all vehicles are auto (drive) relearn. The other two thirds are either stationary relearn or OBD-II relearn.

Here’s something you may not be aware of: A valve-mounted TPMS sensor (snap-in or clamp-in) can be used to replace a banded sensor.

Ford has two relearns available... one for tire rotation which uses the hazard switch to initiate the relearn (listed in the owner’s manual). The other is used when a new sensor has been introduced on a vehicle and uses a sequence of steps to put the vehicle into relearn mode by cycling the ignition switch (this process is not listed in the owner’s manual).

When one or more of the tires are significantly under-inflated, the TPMS indicator will be solid at start-up. If a malfunction occurs (typically a sensor issue), the MIL will blink for 60 to 90 seconds and then go solid. The first step in properly diagnosing a TPMS issue is to note what the TPMS light/MIL tells you at start-up.

Sensors are marked with a frequency identification. Make sure that a replacement sensor features the same frequency as the sensor being replaced. Photo courtesy of 31 Inc.
<p>Sensors are marked with a frequency identification. Make sure that a replacement sensor features the same frequency as the sensor being replaced. Photo courtesy of 31 Inc.</p>

Dave Maclay, director of product management for VDO TPMS, and Sean Lannoo, VDO TPMS sales and tech training specialist, offer this advice:

Dave: One of the things I hear most is the failure of technicians to periodically update their TPMS relearn tools with the latest software required for new vehicle sensors. The tool companies offer these updates frequently, but many technicians don’t update as often, resulting in missing upgrades and new features.

Sean: I’m in the trenches every day. I see many techs not performing relearns on vehicles that require a trigger relearn or when performing tire rotation and don’t perform a relearn.

Note that if you’re dealing with a pressure-by-position system and you don’t perform a relearn, the vehicle will not provide an indication to let you know. The display will not light up.

Also, many don’t seem to understand the difference between programming, relearn and resets. Many use the term “programming” regardless of the actual requirement or procedure.

Certain brands of sensors that are blank require programing. An example of an exception is the REDI-Sensor that doesn’t need programming and only requires a relearn.

A relearn is the process outlined by the vehicle manufacturer that needs to be done whenever a sensor is replaced, moved or rotated. Always perform a relearn.

A reset is a procedure that many indirect systems have. This usually involves a button press or software command, which calibrates as you drive the vehicle.

Here’s a tip regarding relearn attempt. When you’re working on a vehicle and you’ve attempted a relearn two or three times, don’t keep wasting your time. This indicates that something is wrong. You could be performing an incorrect relearn procedure, so don’t assume that you already know the correct relearn procedure. Granted, there might be a recall on those sensors, or you may be faced with a bad sensor, but be sure that you’re following the relearn that’s correct for the specific vehicle. For example, some 2010 Chrysler minivans have a recall that involves the module that receives the signal from the key FOB and the TPMS sensors. Replacing the sensors all day long won’t fix the problem. Make a habit of checking for recalls.

We’re seeing an increasing number of vehicles that feature auto-relearn and an increase in vehicles that feature pressure-by-position systems. These populations continue to grow. If you switch wheel positions on a vehicle that has a pressure-by-position system, you must have a tool in order to do a relearn, but with an auto-relearn system, no tool is needed.

Another tip: Follow the correct relearn procedure for the specific make, model and year of vehicle. Never assume that the procedure is the same for different years of the same make and model. Always refer to the VIN to accurately determine the year, as opposed to the build date. TPMS tools are now available that allow you to scan the VIN bar code to obtain the year. For example, REDI-Sensor has a mobile app that allows you to scan the VIN bar code and look up the OE and the REDI-Sensor sensor part number, as well as providing the specific relearn procedure for an application.

As mentioned earlier, for an indirect system (that utilizes the ABS to differentiate tire diameter changes based on inflation), a reset is required.

Following are tips from Michael Christopherson, BackShop Solutions training manager and special markets for JS Products, gleaned from his conversations with techs during his TPMS training seminars:

  • Toyota and Lexus could have a sensor in the spare. Many lights are cured by properly inflating the spare.
  • Toyotas that were produced around 2006 may not trigger from the TPMS tool due to initiation frequency being on a protected band. The frequency cannot be produced by TPMS tools in the U.S. Releasing air from the tire will trigger the sensor.
  • Many Toyota and Lexus models have Set 1 and Set 2. All sensor positions for both sets need to be filled in the TPMS ECU.
  • On Toyota and Lexus vehicles, the system will be locked if a sensor is replaced and the tire rotation button is pushed. ATEQ and Bartec tools can clear this lock. Afterwards, both Set 1 and Set 2 need to be learned including the spare tire sensor.
  • With vehicles that could have Hi-Line (individual pressure and display) and Low-line (typically a light only) the system must be known before selling sensors.
  • Aftermarket programmable sensors vary in coverage. Always consult the application guide to make sure the chosen sensor will apply to the vehicle.
  • In the Rust Belt states, the customer should be warned that during the service kit replacement process the valve stem could be broken due to corrosion from road salts. Stems and or sensors would need replacement.
  • It is best practice to program the sensor before installing into the rim and airing up. Some sensors lock when aired up and cannot be recovered.
  • Many technicians do not understand the difference between programming and relearning TPMS sensors. Programming involves taking a blank or programmable sensor and giving it an ID and protocol. Relearning involves communicating tire position to the vehicle control system so that tire position is known. Some are stationary learn, some OBD-II learn, some hybrid OBD-II learn and some are auto learn. Technicians commonly make the mistake of believing that all vehicles are auto learn. They may also make the mistake of thinking the relearn process programs the sensor.
  • On many GM vehicles either a key fob, factory tool or enhanced aftermarket scan tool is needed to learn TPMS position. The fob can be tested with modern TPMS tools.
  • Some Mitsubishi vehicles require additional tools to learn the TPMS position. These OBD-II tools put the TPMS system in a learn state.
  • The battery monitor within the TPMS sensor can be misleading. The nature of the lithium batteries used is for voltage to drop off sharply when failing. The battery could show good when in reality it is ready to fail. When one sensor on a vehicle goes bad, they all should be replaced to avoid unpleasant conversations with the customer at a later date.

Three torque-sensitive steps involve using an application-specific torque wrench to tighten the sensor to the stem, valve core and sensor nut. Guessing at the tightness risks damage. Photo courtesy of Bartec USA.
<p>Three torque-sensitive steps involve using an application-specific torque wrench to tighten the sensor to the stem, valve core and sensor nut. Guessing at the tightness risks damage. Photo courtesy of Bartec USA.</p>

How to perform a TPMS inspection and communicate it to your customer, courtesy of Standard Motor Products:

When a customer visits your repair facility for a tire replacement, tire rotation, or TPMS-related concern, your first action before performing any work should be to obtain their information and conduct a quick system check. This extra effort up front will help you explain potential damages later and, most important, ensure that your customer is pleased with their service experience. Here’s what to do:

To start, perform a bulb check by simply turning the ignition key from OFF to RUN. All of the warning lamps on the dash should illuminate and go off in approximately 5 seconds. If not, there’s an error.

Error #1: Low tire pressure telltale (solid light)

If the light remains illuminated, the TPMS system is indicating that one or more tires has an inflation error. Some vehicles (if the previous service provider performed a relearn) provide an additional message indicating the position of the fault. For low tires, check the placard on the vehicle to find the recommended pressure, fill up the tire accordingly, make sure the warning light goes out, and repair the cause of the leak.

Error #2: Malfunction indicator lamp (MIL) (flashing light)

If the light flashes for 60 to 90 seconds during a bulb check and then stays solid, there is a fault with the TPMS system, such as the sensor, receiver or module. Use a tool to retrieve DTCs from the vehicle, or use a TPMS tool to read each sensor.

TPMS relearn

The final step of any tire or TPMS-related work should be a TPMS relearn. This step will ensure that the correct ID numbers are stored in the proper location. In the event of a future fault, the relearn will indicate the correct position to the driver and future repair technician.

Keep an inspection sheet

Once the work is complete and the money is collected, it’s helpful to have an inspection sheet to show the customer. The inspection sheet should document as much information as possible, including customer information, TPMS ID numbers, DTCs, and more. Also, you can use the inspection sheet to inform the customer that:

1) a relearn was performed, and

2) the customer is reassured, knowing their TPMS system is functioning and reporting properly. In the end, this simple communication can go a long way toward ensuring a successful TPMS repair and a happy customer.

Tips to avoid potential issues

1) Always install a plastic valve cap on TPMS sensor valves. Use of a ferrous metal cap may result in signal interference.

2) Never use any type of tire leak chemical or compound to repair an air leak. These materials can clog and contaminate the valve.

3) When installing a TPMS sensor, it is critical to tighten the nut to the specified torque value using a dedicated torque driver. Over-torquing can easily damage and strip valve threads.

4) Avoid the use of inexpensive “stick type” air pressure gauges. The mechanical operation and calibration level of this gauge style can vary and may not provide the necessary accuracy. A quality needle-gauge analog or digital gauge that compensates for temperature is preferred. Inaccuracies of as little as 3 psi can result in incorrect tire pressure readings that can affect the TPMS warning light. Double-checking pressure with a TPMS scan tool that reads air pressure can verify the calibration of your air gauge.

5) When two like-vehicles are parked close together, the relearning process could assign an incorrect sensor to the vehicle. When programming sensors, stand far away from sensor storage. Another sensor may be programmed or multiple ones could be programmed. Always test a sensor after programming.

6) Don’t guess or assume. It’s vital to verify that the TPMS is working properly before installing the new tires. If the system isn’t working properly and the vehicle is returned, the customer may experience system-related issues and wrongly assume that the cause is due to a shoddy tire install. To avoid issues, always test instead of guess. With your TPMS tool at the ready, turn the ignition key to the run position, and enter the vehicle’s TPMS Learn Mode. On many applications, you simply need to press the “lock” and “unlock” buttons on the key fob and wait for the horn to chirp twice. Once the vehicle is in TPMS Learn Mode, enter the vehicle make, year, and type of sensor. Then, work your way around the vehicle testing each sensor. The TPMS tool will display the sensor’s pressure, temperature, sensor ID, battery life, and other important information. If there’s an issue, address it now before you perform a tire swap.

7) Perform a road test. When you have a customer’s vehicle that has been equipped with non-TPMS steel wheels and winter tires for the winter season, the TPMS warning light will remain illuminated. When it’s time to reinstall the OE wheel and tire package, the warning light will flash (depending on the specific vehicle) for about 1 to 2 miles of the first drive cycle, at which time the light will (should) go out. To avoid premature complaints, after installing the OE package, take the time to road test in order to both verify operation (checking for vibrations, steering, braking pull, etc.) and to allow the TPMS warning light to go out. If you allow the customer to drive away without confirming that the light is not on, he or she may return immediately, complaining that “there’s something wrong with the TPMS.”

8) Sensor battery life is estimated at seven to 10 years. Considering that the OEs have been installing TPMS in vehicles since 2007, it’s time to start seeing dead sensor battery issues. In terms of the need for sensor replacement, the demand for new sensors should start booming. As these systems age and evolve, it is absolutely essential for your shop to not only possess a TPMS tool, but to stay updated with OE changes, recalls, and to avoid mistakes that can create frustration and extend diagnostic time.    ■

Tire Pressure Monitoring System Relearn Information

There are three types of relearns: stationary, OBD and auto. Approximately 25% of applications use an activation tool with the vehicle in the “re-learn” mode. New IDs can be programmed without driving the vehicle. About 36% use an activation tool in conjunction with a scan tool in order to program new sensor IDs into the vehicle. New IDs can be programmed without driving the vehicle. About 39% of vehicles can learn a single new ID and in some cases multiple IDs without the use of a tool, requiring driving the vehicle in order to turn off the warning light. TPMS tools are available that function both as a scan tool and sensor activation tool.

Less than 40% of vehicles can currently reset themselves. Some auto learns can only do one TPMS sensor.

Hyundai, Infiniti, Kia, Mercedes, Lexus, Nissan, Subaru, Suzuki, Acura, Mitsubishi, Honda and Toyota are some of the vehicle makes that require a scan tool to complete the relearn.

To read more on TPMS, see:

Profiting from TPMS Service

TPMS Tips: Identifying Types, Applications, Functions and Service

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