BMW steering switch unit and steering angle sensor may fail.
BMW TPM light or warning message may come ON when there is a loss of air pressure in one or more tires.
As a BMW Tire Pressure Monitoring System detects a 20% loss in tire pressure, it triggers a TPM warning to alert the driver.
If the tire pressure is correct, you may be getting a TPM malfunction or inactive errors because:
- TPMS sensor is defective
- RDC module is faulty
- External interference
What to do?
If you are getting tire pressure warning message, the first thing you need to do is to check the tire pressure with a tire pressure gauge.
Inflate all the tires as recommended on the tire pressure label that can be found on the driver's door frame or behind the gas cap access panel. The typical BMW tire pressure is 32-36 PSI.
How does BMW TPM work?
The TPM has pressure sensors in each wheel and a control unit ( also known as RDC, TPM, TPMS receiver) is installed in the vehicle.
This system monitors tire pressure and warns the driver if the pressure is too low. Proper tire pressure (typically 32-36 psi) will ensure the best performance, fuel economy and extended tire life.
Defective RDC Transmitter
Older BMW models, with generation 1 or generation 2 TPM systems, have a sensor within the tire and a transmitter in each wheel well, hidden behind the underliner.
Transmitters pick up the signal from sensors and send them to the central control unit, which has an antenna. In most cases, a transmitter can go bad, causing a break of communication.
It is also possible for a reception antenna in the control unit to fail.
Newer BMW models, equipped with generation 3 or later TPM systems, use a more simplified system. With no wheel transmitters, wheel sensors combined with a single control unit that has an integrated antenna are the only components.
Depending on the model year, the control unit is mounted on the chassis, which makes it exposed to the elements. As a result, moisture enters the casing, causing corrosion on sensitive electronic components.
Although sealed, the control unit can be opened with a bit of effort. Clean any traces of corrosion, which are green in most cases.
BMW tire pressure module (A85a) may be installed under the spare tire or under the dashboard on the driver's side.
A common problem with BMW tire pressure system is when the RDC module is installed under the spare tire in the trunk floor.
Water can build up under the spare tire which in turn damages the module or causes corrosion to the contacts.
Lastly, check the TPM fuse, as it can burn if the control unit shorts out.
In most models, this fuse is located in the junction box behind the glove compartment.
TPM Sensor Battery
Within each tire, there is a sensor that gives information about the air pressure.
They have a lithium-ion battery, which drains out with time. In most cases, OEM batteries can last up to 10 years.
Another possibility is mechanical damage, which can happen during tire fitment.
Most tire shops have wireless readers that can verify if the sensor is emitting the signal.
Reset BMW TPM warning
The next step is to reset the TPM warning.
- Inflate the tires to the recommended tire pressure. Typically 36 PSI.
- Press the iDrive knob to select vehicle settings.
- Scroll down to Vehicle Tires using the iDrive knob.
- Rotate the iDrive knob to select the TPM menu.
- Select Reset then press the iDrive knob.
- Select YES. The status should change to Resetting TPM.
- After a short drive Status should change to TPM Active.
Because of various transportation acts, a TPM system is mandatory for all new cars sold in the United States after September 2007. So, all BMW cars from 2008 have a TPM system installed from the factory, regardless of the model and equipment level.
Possible Error Messages
- Tire Pressure Monitor TPM for the detection of flat tires is currently unavailable. Please contact the nearest BMW
- TPM Status: TPM Malfunction
- Tire Pressure Monitor (TPM) malfunction:
- System unable to detect tire pressure loss
- Check tire pressure manually
- Continued driving is possible
- Consult service center
- Tire Pressure Monitoring malfunction: Drive moderately. The system is unable to detect tire pressure loss. Consult service center.
- TPM Inactive warning light on the dashboard.
- Tire pressure monitor reset: System inactive and unable to detect pressure loss for up to 12 minutes. Reset only occurs while driving.
- Low tire pressure. Stop carefully. For Run Flat tires with the "RSC" symbol, you can continue driving with max. 50 mph (80 km/h).
Diagnose BMW TPM System
To diagnose BMW tire system malfunction you will need an OBD-II scanner that can read and clear BMW specific fault codes.
Generic OBD-II scanners won't be able to read BMW TPM fault codes such as:
- 604E RDC System Malfunction
- 6050 RDC Transmitter, front right
- 6055 Wheel electronics, front right
TPMS and Run-Flat Tires
In addition, most new BMW cars have run-flat tires, an inoperable TPM system can be a safety issue.
Depending on the type, cars with run-flat tires can drive up to 55 mph and up to 200 miles in distance with underinflated tires.
While conventional tires have soft sidewalls that deflate when unpressurized, a run-flat tire has a strong sidewall structure.
However, as these tires can support the weight of the car and maintain their shape with no air inside, a driver might not notice a punctured tire.