The wheel sensor electronics are the most common fault in the TPM system. The sensor is either mechanically damaged, or the battery dies. In any case, the solution is to replace the defective sensor. While this will happen in more than 90% of cases, sometimes diagnostics become complicated.
- A FAULTY WHEEL SENSOR IS A MOST COMMON FAULT
- A FAULTY SENSOR IS OFTEN REPLACED WITH AN INCORRECT VERSION
- YOU CAN TEST SENSORS ONLY WITH RDC TOOL OR SCANNER
- THE SENSOR’S BATTERY LIFE IS ABOUT 10 YEARS
- ON MODELS WITH EXTERNALLY INSTALLED RDC MODULES, THE WATER CAN INGRESS AND DAMAGE THE MODULE
- 5TH GEN TPM SYSTEM (INTRODUCED IN G20) REQUIRES SENSOR PROGRAMMING AFTER THE SENSOR IS DEPRESSURIZED FOR MORE THAN TWO MINUTES
- Step-by-Step Diagnostics
- How The TPM System Works
- The Evolution of The BMW Tire Pressure Monitoring System
- Most Common BMW TPM Problems
Because people can’t hear and interpret radio signals sent at either 315 or 433MHz, you’ll need a capable diagnostic scanner to read out the fault memory or a TPM tool to read sensor signals directly.
While the most common fault with every TPM generation is a faulty wheel sensor, the early Gen 1 and Gen 2 systems are more prone to other electrical gremlins because the systems are much more complicated and the cars are much older now. So, keep in mind that troubleshooting TPM faults on a tortured 2002 E65 are not as simple as it is on a well-maintained 2016 F30.
While the latest Gen 5 TMP system is as reliable as it gets, in most cases troubleshooting TPM faults will require expensive specialty tools like RDC Tool connected to ISTA Next. I guess this is the reason why there are so many “TPM won’t reset” problems with G20 and later 2020 and newer series. The most common cause is that the wheel sensor must be programmed with every tire change.
In the example below, we’ll take a look at how to diagnose and fix the most common fault on BMWs equipped with Gen 3 TPM system. Later I’ll cover each generation and the typical problems that come with each.
STEP 1 – READ OUT FAULT MEMORY
First, connect the scanner and read out the fault memory (DTC). Any malfunction will trigger a fault code. For this, you can use and generic scanner with a function to communicate with your BMW’s RDC module, some of many BMW diagnostic apps like Pro Tool, or the BMW ISTA.
For the most common simple faults like failed wheel sensors, most scanners will do. However, when things get tough, there are no substitutes for ISTA test plans.
In this case, we found out that the faulty component is the front right wheel electronics (sensor). So, to fix the fault, we need to source a new sensor, replace it and reset the TPM tire pressure.
While exchanging the information with the RDC module it’s a good time to check the state of other sensors’ batteries. I don’t know about other tools, but with the ISTA you can check the state of each sensor’s battery. In fact, the ISTA will show you how much of the battery life is left in a one-month accuracy.
STEP 2 – FIND THE RIGHT PART
With the DTC in your hands, you can move on to the problem fix. So, let’s solve the problem with inoperative wheel electronics.
Note! When only one wheel sensor fails, the whole TPM system becomes inoperative – you won’t see the tire pressure from the other three working sensors.
So, as we established that the fault is in the sensor, now we have to find the right part. Also, have in mind that the wrong sensor installs happen quite often, especially if you go aftermarket or eBay route. Luckily, with the BMW’s part catalog ETK you can’t go wrong, assuming there are no modifications on your car.
The easiest way is by using dealer ETK connected to BMW servers, as it will automatically determine which part is installed in your car.
In this example, we can see which part is installed in our G30 according to VIN.
However, if you use free online part catalogs like RealOEM, or the ETK application not connected to the BMW server, you’ll have to be careful to pick the right part.
As you can see above, while the ETK offered us only one part, here we have to choose between 433MHz and 315MHz versions. The reason is that these apps don’t have access to the Vehicle Order, which contains all relevant data on equipment installed in a specific car. So, to make sure which sensor fits your car, you’ll have to look up vehicle equipment codes – in this case, SA876.
There are also differences based on production date. For example, the F10 5 Series uses both the Gen 2 and Gen 3 TPM systems, depending on the production date. The F30 3 Series use both Gen 3 and Gen 4. That is, you can’t buy a wheel sensor based on a model series alone and hope you got the right generation.
STEP 3 – REPLACE THE SENSOR
Unless you have a tire machine at your disposal and know how to use it, you’ll have to visit the tire shop. To replace the TPM sensor the tire must be at least half dismounted and most tire shops will charge you about $30 for the labor. Below is the TPM sensor replacement procedure example for RDCi Gen 4 wheel electronics.
Remove the tire completely or at least the outer bed.
Release the union nut.
Remove the sensor from the valve hole and clean the valve sealing surface.
On a new sensor put the sealing ring before installing it on the rim (RDCi example).
Insert the new sensor into a cleaned valve bore. Both outer feet on the underside of the sensor electronics must be resting against the rim wall.
Screw on union nut (1) by hand as far as it will go.
The screw connection must be tightened to the specified torque in one go!
Do not under any circumstances retighten the screw connection!
Torque specs for tightening the valve to the rim:
|Gen 3||RDC Low||3.5||2.6|
Fit the tire back.
STEP 4 – RESET THE TPMS
Depending on the model series, there are three ways to reset the TPM tire pressure:
- Via iDrive’s menu (all models with iDrive)
- Via instrument cluster board computer menu
- Or by pressing and holding the TPM button in the center console for four seconds
The initialization of the TPM system must be performed in the following cases:
- The tire pressure is adjusted
- Following a wheel swap (for example, summer/winter tires)
- Wheel exchange between axles
The existing inflation pressure is set as a specification for the nominal pressure during the initialization process. That is, there are no preset pressure values; you can choose anything as long as it is greater than 27 psi / 1.85 bar (1.7 bar for Gen 1 and 2) and set chosen pressure as the nominal value.
On some later models (G-Series) you’ll find the recommended tire pressure directly in iDrive, whereas on older models (E/F-Series) you must look up the recommended tire pressure on a label located on the driver’s side B pillar.
|2||Tire size dimensions|
|3||Cold tire pressure|
COLD TIRE PRESSURE: The cold tire pressure means that the tire air temperature is the same as the current ambient temperature. The pressure values you find on either the tire pressure sticker or in the iDrive refer to cold tire pressure.
WARM TIRE PRESSURE: During the longer drives the tire warms up due to friction with the tire surface and tire creep. The tire pressure increases with the temperature increase for about 1.45psi/0.1 bar for every +50°F/+10°C of temperature increase.
In short, always set the tire pressure before a lengthy drive.
How The TPM System Works
Actual tire pressures have been monitored since the introduction of the first active tire pressure monitoring (TPM) system in the E65 7 Series. The tire pressure is measured by wheel sensors and transmitted via radio signal to a TPM control unit and then presented via iDrive display. Since the introduction of the E65, the BMW has gone through five TPM generations.
The Evolution of The BMW Tire Pressure Monitoring System
In response to tire safety concerns – the leading tire manufacturers were involved in numerous lawsuits involving catastrophic tire failures – the United States Congress passed the Transportation Recall Enhancement, Accountability, and Documentation (TREAD) Act in November 2000.
Aside from many other industry aspects included, TPM was one of the primary components of the TREAD Act. The reasoning is that if the tire pressure loss can be detected before it affects the handling and safety, there would be fewer catastrophic events caused by tire failures.
Initially, the NHTSA approved the installation of indirect TPM systems. Indirect TPM systems monitor tire pressure “indirectly” by monitoring the rotational speed of the tire via the wheel speed sensors. The ABS/DSC system can then detect pressure loss by comparing wheel speed information between all 4 tires. Any loss in tire pressure would result in a change in tire diameter and therefore a change in rotational speed.
Flat Tire Monitor System (FTM/RPA)
FTM Systems are an “indirect” system used for the first time on the 2000 E39 M5.
Source: BMW Service Training
The early FTM systems on BMW models such as E39 M5, E52 Z8, and E46 Xi used a separate control module that received wheel speed signals from the DSC module. The operating software was later integrated into the DSC module or iDrive head unit (only E65 7 Series).
The FTM does not measure tire pressure but only the wheel rotational speed. A difference in wheel speed is recognized as a pressure loss. The FTM can detect the pressure loss of about 20-40% of the initial value.
The problem with the FTM system is that it cannot detect a uniform drop in pressure from all four tires due to natural diffusion.
The guidelines of the TREAD Act found that “Indirect” TPM systems are ineffective in
detecting tire pressure loss until the tire was under-inflated to an unsafe level. Therefore,
NHTSA mandated that auto manufacturers install “Direct” TPM systems on all vehicles sold in the US.
As per NHTSA guidelines, passenger cars and light trucks must have the “Direct” TPM
systems installed via a specific timeline from 2005. By 2007, all auto manufacturers must
be in 100% compliance.
TPM Generation 1 (2001 – 2006)
Source: BMW Service Training
The first-ever BMW to use a “direct” TPM system was the E65 7 Series. The system was then called Tire Pressure Control or RDC. The E46 3 Series also received the RDC system as an option.
This system appears to be quite complicated today. In addition to the TPM sensor in each wheel (1, 4, 7, 10) it has four antennas (2, 5, 6, 9) located in the wheel housing that receives radio signals from the wheel sensors and transmits them to the RDC aerial (8). The data is then transmitted to the RDC control unit via the K-CAN/K network (3).
Despite the use of long-life lithium-ion batteries, they typically lasted about five years, if not less. The reason for this is that TPM sensors are always active, even when sitting on a spare parts shelf in an energy-saving mode. In contrast to modern TPM systems, the Gen 1 system can take up to half an hour or more to initialize after a reset.
Gen 1 Tire Pressure Reset Procedure
In BMWs without the iDrive, the RDC is reset via a button in the center console control panel. This TPM button must be held down for four seconds.
The RDC on iDrive vehicles is reset via the menu option: Settings → Vehicle → RDC → Reset. In general, the reset can be performed with the ignition or engine turned on only when the vehicle is stopped. The TPMS initialization process can take up to 30 minutes of driving time.
TPM Generation 2 (RDC) 03/2006 – 09/2010
The Gen 2 TPM is a trigger-type system. Instead of having four antennas at each wheel, the Gen 2 uses trigger modules. Each of the sensors has its own ID which is sent to the central receiving antenna. In this case, the TPM wheel sensor only sends the date when requested by the TPM module.
TPM Generation 3 (RDC Low) 09/2010 –04/2013
This is a very clever design that only has five components. The name “Low” refers to “low cost” – there are four sensors and an RDC module with an integrated antenna. This is one of the most reliable systems.
The messages sent by the wheel electronics are processed by the RDC control unit. The electronics on each wheel send the following messages:
- Tire inflation pressure
- The temperature of tire air
- Remaining battery life
- Data from the acceleration sensor
- Identification Feature (ID) of the wheel electronics
These messages are then sent directly to the RDC control unit via a high-frequency transmission path (433 MHz) and evaluated. The wheel electronics’ measuring cycle is 3 seconds, with transmission to the RDC control unit every 30 seconds. The current message status is sent to the CAN bus (body CAN) and is then displayed by the indicating instruments. The RDC control unit is installed in the outer area of the vehicle underbody behind the rear axle.
Source: BMW ISTA screenshot
TPM Generation 4 (RDCi) 04/2013 –
In 2013, the F32 4 Series Coupe was the first model to receive the Gen 4 RDCi TPM system. The RDC antenna has been relocated under the rear shelf of the vehicle, and the module has been integrated into the DSC control unit for increased reliability.
Source: BMW ISTA screenshot
TPM Generation 5 (RDCi) 2019 –
With the current G20 3 Series, the latest TPM generation was introduced. The most noticeable difference between this generation and previous generations is the addition of QR-code tires and programable TPM sensors.
Most Common BMW TPM Problems
Wheel Sensor Don’t Send Signal Due to Dead Battery
Wheel electronics battery will usually last for about ten years. When only one battery dies the whole TPM system becomes inoperative. When this happens often is only one sensor replaced, only to get the same TPM warning light in a few weeks again. The reason is that very often only one sensor will fail and throw a code for it. The problem is that this sensor with a dead battery can’t communicate to the RDC module and report that problem is in the battery.
Pro Tip: While carrying out the vehicle test, always check the remaining battery life for all of the wheel sensors.
Mechanically Damaged Wheel Sensor
This happens while changing tires and this can happen even to experienced tech. I don’t know how to change the tire and I certainly don’t want to learn how. I’ve watched it many times and I’ve seen in the flesh how easy is to damage the wheel electronics while changing the tire, especially the UHP run flats in 20’’ and above dimensions.
The diagnostics fault code will be the same as with a dead sensor battery.
The Wrong Wheel Sensor is Installed
These problems happen more often than you think. They very rarely happen at BMW dealers since they use the ETK and would get the wrong part only if the car is not equipped with the TPM system as it left the factory. For as long as I can remember, I never ordered the wrong TPM sensor. And I ordered a lot of them throughout the years.
However, they very often happen when people source the parts by themself.
Because the TPM generations overlap in the same BMW series, it’s easy to source the wrong part. I’ve seen this also happens when the new BMW series came out and the tire shops are still not familiar with them.
Some tire shops and online shops sell generic wheel sensors that can be programmed to match the vehicle system. The problem happens when the sensors are programmed for the wrong TPM system.
5th Gen RDCi Sensor Needs to Be Programmed
The latest 5th generation TPM sensors must be programmed after tire or sensor replacement or the tire has been flat for more than two minutes. We had a lot of G20 owners complaining about TPM warning messages after tire replacement or when changing winter and summer tires.
Unlike all of the previous generations that required no programming whatsoever, the Generation 5 Huf sensors must be programmed with an RDC tool. The reason is that Gen 5 sensors store much more information about the tires.
Yes, you can use the aftermarket tires, but the sensors still need programming.
In addition to TPM sensor programming, the RDC tool includes a feature for registering tire replacement via a QR code on the tire side wall. No really, we now have to register the replacement of the tire in addition to the battery, starter, spark plugs, glow plugs, and many other parts.
Then you can check how much tread is left on your tires in your myBMW app. I’m not sure how this could work, but I applaud them for trying it. I can only hope that this tire wear prediction does not work the same way that the brake pad prediction did.
If you choose to install aftermarket tires for whatever reason, the warning in the myBMW app will remain for 60 days.
Faulty RDC Module Due to Corrosion
Both Gen 2 and Gen 3 TPM systems use the RDC module installed under the car exposed to all kinds of outside influences. Although they are made to be waterproof, water can find a way inside a sealed box and corrode the electronics. The test will reveal no communication with the control unit.
The solution is to replace and code the RDC module. In some cases, it can be repaired, but in my opinion, it’s not worth the hassle, since they sell for about $50 used or $150 new. Just make sure you source the right generation.
Corroded Wiring, Antennas, Triggers, And Sensors
In older generations 1 and 2, the wiring and connectors often corrode due to age or wiring damage, and quite a complex system when compared to newer generations. Troubleshooting wiring issues takes the most time of all other faults.
Also, in these older generations, most faults are not typical and will require individual diagnostic plans to solve the problem. The best way is to follow ISTA test plans, as they’ll get you the fastest to the root cause.