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2021 M340i Brake Fluid Flush & Pad Sensor Reset Issues After DIY Pad Change

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Mike T. · rep 0 · May 25, 3:02 AM · 1 replies · solved · Question

Vehicle: 2021 BMW M340i (G20)

Hello Bimmer community! I've got a 2021 BMW M340i (G20) with about 40,000 miles on it. The iDrive system is currently telling me it's time for a brake fluid flush, and I also recently replaced my front brake pads and rotors myself. I made sure to replace the front brake pad wear sensor with a brand new one.

However, after replacing the sensor and trying to reset the service interval in iDrive, it's not clearing the brake pad warning. The brake fluid flush warning is also still present, even though I haven't done it yet, I just want to clear the pad warning first. I tried the usual pedal-hold method in the service menu, but no luck; it just shows a red clock icon.

Am I missing a step for resetting these service lights on a G20? Is there a specific sequence or tool needed, like a diagnostic scanner, to properly register the new sensor and clear the brake fluid warning? Any help would be greatly appreciated!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 3:02 AM

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ClearTheCode admin answer:

It's great that you're tackling your own brake maintenance on your 2021 BMW M340i (G20)! Resetting service indicators, especially after replacing wear items like brake pads and sensors, can sometimes be tricky on modern BMWs. The red clock icon usually indicates a failed reset attempt.

Brake Fluid Flush:

  • BMW recommends a brake fluid flush every two years, regardless of mileage. The iDrive system tracks this time-based interval. The warning will only clear after the flush is performed and the service interval is successfully reset.
  • Reset Procedure: After performing the flush, the reset is typically done via the iDrive service menu. You'll need to select the brake fluid service item and hold the BC button (or the button on the turn signal stalk) until 'Reset' appears, then confirm. Ensure the engine is running.

Brake Pad Wear Sensor & Service Reset:

  1. Correct Sensor Installation: Double-check that the new brake pad wear sensor is correctly plugged into both the brake pad and the vehicle's harness. A faulty connection or a cheap aftermarket sensor can prevent the reset.
  2. Reset Procedure: For the brake pad service, the process is similar to the brake fluid. With the engine running (or ignition on), navigate to the service menu in iDrive, select the relevant axle (front or rear brake pads), and hold the BC button until 'Reset' appears. Confirm the reset.
  3. Common Issues: If the reset fails, it often points to a problem with the new sensor itself, its connection, or occasionally, a damaged wiring harness leading to the sensor. The system needs to see a closed circuit from the new sensor to allow a reset. If the old sensor was completely worn through, the circuit was open, and the new sensor needs to re-establish that connection.

When to See a Shop:

  • If repeated manual reset attempts fail, even with a confirmed correct sensor installation, a diagnostic tool (like ISTA, Autel, or Foxwell for BMW) might be needed. These tools can often force a reset or provide specific fault codes that indicate why the reset is failing (e.g., 'Sensor Circuit Open').
  • A shop can also perform a diagnostic scan to check for any stored brake system fault codes (though a simple wear sensor issue usually doesn't generate generic OBD-II codes, but rather BMW-specific fault codes). They can also ensure the brake fluid flush is done correctly, including proper bleeding to remove air from the system.
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