Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
System function of RDC
The Tire Pressure Monitor (RDC) is a system for monitoring the tire pressure when driving. It is offered exclusively in the USA (legal requirement) and as an optional extra in Canada.
The tire inflation pressure to be monitored is specified by the driver. He or she instructs the system via the control function in iDrive to save the current tire inflation pressure as the target pressure value (Reset). The plausibility of the setpoint value is checked before the RDC control unit adopts it (axle-wise comparison of the nominal pressures, minimum pressures). A reset is only possible when the tire pressure on all wheels is at least 1.6 bar. If the tire pressure of one wheel falls below this limit, a Check Control message is issued immediately. If the pressure difference between the wheels on one axle is > 0.4 bar, the reset is rejected following a plausibility check. A Check Control message is output. Remedy: set tire pressures to the correct values and then run the reset once again.
Internal sequence after activated adaptation process (reset):
- Recognition of the fitted wheel electronics systems
- Identifying the position of the wheel electronics systems
- Plausibility check by checking the target pressures
- Adoption of the specified pressures as nominal pressures
On comparison of the current tire inflation pressure with the target pressure, the air temperature is taken into account. On the basis of the nominal pressure and temperature during the reset, the RDC calculates the limit values for the tire pressure. The tire pressure increases by 0.1 bar per 10 °C increase in temperature. If the temperature-evaluated limit values are not reached, the RDC issues a Check Control message.
| Item | Explanation |
|---|---|
| 1 | RDC transmitter, rear right |
| 2 | RDC control unit |
| 3 | RDC transmitter, rear left |
| 4 | RDC aerial |
| 5 | RDC transmitter, front left |
| 6 | RDC transmitter, front right |
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.