What Does C1125 Mean?
This code indicates the ABS control module has detected a failure in the brake fluid level sensor input circuit. The brake fluid level sensor, typically a float-type switch mounted in the master cylinder reservoir, provides a critical safety signal to the ABS module indicating whether brake fluid is at an adequate level. When this circuit fails, the module cannot verify fluid level and may disable ABS operation as a precaution.
Safety Warning
If brake fluid is actually low, braking performance may be severely compromised. ABS is likely disabled. Do not drive until fluid level and potential leaks are verified. Immediate repair required.
Common Causes
35%
Failed brake fluid level sensor due to worn float mechanism or corroded internal contacts
25%
Corroded or damaged wiring between the fluid level sensor and the ABS module, often from brake fluid exposure
20%
Poor connector contact at the sensor or ABS module due to corrosion or terminal push-back
15%
Brake fluid level is actually low due to worn brake pads or a hydraulic leak, triggering the sensor legitimately
5%
ABS control module internal circuit failure on the fluid level input
Diagnostic Steps
1
Step 1: Verify actual brake fluid level in the master cylinder reservoir. If low, inspect all four brake corners for fluid leaks at calipers, wheel cylinders, brake lines, and hose connections before proceeding with electrical diagnosis.
2
Step 2: With the ignition on, disconnect the fluid level sensor connector and use a multimeter to check for reference voltage (typically 5V or 12V) on the supply wire from the ABS module.
3
Step 3: Test the fluid level sensor itself by measuring continuity across its terminals — it should be closed (continuity) when the float is up (fluid full) and open when depressed (fluid low). Replace if readings are inconsistent.
4
Step 4: Check wiring continuity from the sensor connector to the ABS module connector. Test for shorts to ground and shorts to battery on both wires.
5
Step 5: Clear codes, verify fluid level is correct, and test drive. Monitor for code return.
Estimated Repair Cost
$50 - $250
Parts + labor, varies by vehicle and location
This code indicates the ABS control module has detected a failure in the brake fluid level sensor input circuit. The brake fluid level sensor, typically a float-type switch mounted in the master cylinder reservoir, provides a critical safety signal to the ABS module indicating whether brake fluid is...
The most common cause of C1125 (Brake Fluid Level Sensor Input Circuit Failure) is: Failed brake fluid level sensor due to worn float mechanism or corroded internal contacts
Typical repair costs for C1125 range from $50 to $250, depending on the vehicle, location, and whether you do it yourself or go to a shop.
If brake fluid is actually low, braking performance may be severely compromised. ABS is likely disabled. Do not drive until fluid level and potential leaks are verified. Immediate repair required.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to C1125 to identify the root cause.
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Quick Info
Category
Chassis
System
Anti-lock Brake System (ABS) / Brake Hydraulic System
Difficulty
Type
Manufacturer
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