Last morning, I repaired a New Ford Focus with only 85 miles on it. The car owner Chen called me at around 7 a.m. and told me dashboard warning light on with message “Brake Fluid Level Low”. According to the car owner, the problem had happened twice before. “The problem occurred when I started the car in the last two mornings. But the car braking was fine. And the light would turn off if I kept on driving for a while.”

New Ford Focus dashboard warning light on with message “Brake Fluid Level Low”

Chen told me he only had half an hour left and hoped I could fix the problem as soon as possible. Time was limited. To find out the problem quickly, I decided to troubleshoot the vehicle braking system first with a Ford OBD2 tool, GNA600 VCM IDS. No fault code was retrieved. Then I checked the brake fluid level, which was later found fine, so as braking line.

Since the problem only occurred sometimes, I asked Chen for more details. Chen told me he had ever parked the car on a slope; maybe that was the reason. I simulate a field test, but did not get any code again. My guess was the problem was with the brake fluid level sensor.

So I disconnected the sensor, and went on a test drive. The dashboard warning light turned on suddenly. Then I put the sensor back, and the light did not come up. This indicated that the communication between BCM and IC was normal. I tested the resistance of the sensor. When the brake fluid was at right level, the resistance was 1.2n. However, for a new car, the resistance of the sensor should be within 0.2n to 0.3 n.

At this moment, Chen told me to hurry up because he was about to late for work. If I was not mistaken, the diagnosis was almost done. Since I am pressed for time, I decided to replace the sensor first, rather than tested it with Ford VCM IDS.

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