What Does C1189 Mean?
The brake fluid level sensor input circuit is shorted to ground. The ABS module sees a constant low (ground) signal on the sensor input, which may cause it to interpret the fluid level as critically low regardless of the actual level. The brake warning light will be on, and ABS may be disabled as a safety precaution.
Common Causes
35%
Sensor signal wire chafed through to chassis or body ground
25%
Brake fluid level sensor internally shorted to ground
20%
Water or brake fluid contamination in the sensor connector creating a ground path
15%
Pinched or damaged wire at the firewall grommet or harness routing
5%
ABS module ground-side sense circuit failure
Diagnostic Steps
1
Verify the brake fluid level is adequate. If it is actually low, the sensor may be correctly reporting — address the underlying cause (worn pads, leak) first.
2
Disconnect the brake fluid level sensor. If the code changes to open circuit (C1187), the sensor is shorted internally — replace it.
3
With the sensor disconnected, measure resistance from the signal wire in the harness connector to chassis ground. It should be OL (open). A low resistance reading confirms a wiring short to ground.
4
Inspect the harness from the sensor to the ABS module, focusing on areas where the wire passes near metal edges, through grommets, or near the master cylinder where brake fluid could drip onto the wiring.
5
If no harness fault is found, clean the sensor connector thoroughly with electrical contact cleaner and dielectric grease. Moisture alone can create enough conductivity to trigger this code.
Estimated Repair Cost
$25 - $300
Parts + labor, varies by vehicle and location
The brake fluid level sensor input circuit is shorted to ground. The ABS module sees a constant low (ground) signal on the sensor input, which may cause it to interpret the fluid level as critically low regardless of the actual level. The brake warning light will be on, and ABS may be disabled as a ...
The most common cause of C1189 (Brake Fluid Level Sensor Input Short Circuit To Ground) is: Sensor signal wire chafed through to chassis or body ground
Typical repair costs for C1189 range from $25 to $300, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The brake warning light may be on with the system reporting false low fluid. This masks any real fluid level warning. Manually check brake fluid before driving. ABS is likely disabled. Conventional brakes work as long as fluid level is actually adequate, but repair promptly to restore fluid monitoring.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to C1189 to identify the root cause.
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Quick Info
Category
Chassis
System
ABS / Brake Hydraulic System
Difficulty
Type
Manufacturer
Recommended Tools
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