C0128

Step 1: Perform visual inspection of brake fluid level in master cylinder reservoir. Check if fluid is at or below the MIN line. Inspect entire brake system for visible leaks at master cylinder, brake lines, calipers, wheel cylinders, and ABS unit.

Step 2: Inspect brake fluid level sensor and wiring harness at reservoir cap for physical damage, corrosion, or loose connections. Check connector terminals for moisture, corrosion, or bent pins.

Step 3: Using a digital multimeter, backprobe the sensor connector and measure voltage or resistance values according to manufacturer specifications (typically 0.5-1.0V for low fluid condition). Compare readings with sensor float manually moved between high and low positions.

Step 4: If voltage readings are correct at the sensor but code persists, check continuity and resistance of the wiring harness between the sensor and ABS/chassis control module. Look for opens, shorts to ground, or high resistance (should be less than 5 ohms).

Step 5: If fluid level is low, top off with proper DOT-rated brake fluid and inspect brake pad/shoe thickness at all four corners. Measure pad thickness with caliper (minimum typically 2-3mm). Check for evidence of fluid consumption or leaks that caused low level.

Step 6: After repairs, clear codes and perform test drive with multiple brake applications. Monitor live data for brake fluid level sensor status and verify code does not return. Check brake pedal feel and travel for normalcy.