Rdc Module or Wiring Fault
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The RDC module is BMW's tire pressure monitoring system control unit. When it loses power, ground, CAN bus communication, or antenna wiring to the sensors, the dashboard shows a TPMS warning or malfunction lamp. This cause becomes more likely if the warning is constant rather than intermittent, sensor-specific rather than all four tires, or paired with a separate module fault code.
What it feels like
You'll see a yellow or amber TPMS warning light on the dashboard, sometimes with a message like "Check TPMS system" or a specific tire graphic highlighted. The warning may appear after startup and stay on, or show only certain tire sensors as faulty. Unlike a true low-pressure warning, which often clears after driving or warming up, a module or wiring fault tends to be constant. Some owners report the warning flashing intermittently if wiring is loose or corroded, especially after temperature swings or vibration.
How to confirm it
- Connect a diagnostic scanner to the OBD-II port and pull fault codes from the RDC/TPMS module. Look for module faults (power, ground, or CAN) versus sensor-specific faults. Note the fault code number and whether it repeats.
- Check the RDC module power supply and ground pins at the module connector. Use a multimeter to confirm 12V on the main feed and less than 0.1 ohm to chassis ground. Low or absent power confirms a power-side fault.
- Inspect the K-CAN high and low signal wires into the RDC module for continuity using the multimeter. Breaks or very high resistance point to a wiring open or corrosion.
- Visually trace the antenna wiring and sensor signal cables from the RDC module to each wheel well. Look for chafing, pinched spots, cracks in insulation, water intrusion, or loose connectors. Reseat any loose pins or connectors found.
- If power, ground, and CAN communication test good but the fault code remains, the RDC module itself is likely faulty and requires replacement.