What Does C1103 Mean?
This code indicates the ABS control module has detected an electrical fault in the hydraulic brake pressure switch circuit. This switch monitors brake pedal application and hydraulic pressure within the ABS system to coordinate proper ABS operation. The control module detected either an open circuit, short circuit, or implausible signal from the brake switch that feeds into the ABS hydraulic unit.
Safety Warning
This is a critical safety issue as ABS functionality may be disabled or operate improperly, potentially causing loss of vehicle control during emergency braking situations. The vehicle may still have basic braking but without anti-lock capability. Repair should be performed immediately and aggressive driving should be avoided.
Common Causes
40%
Failed or misadjusted brake light/pressure switch at brake pedal assembly
30%
Damaged wiring harness or corroded connector between brake switch and ABS module
20%
Failed ABS hydraulic control unit internal pressure switch or sensor
10%
ABS control module internal fault or software corruption
Diagnostic Steps
1
Step 1: Visually inspect brake pedal switch at pedal assembly for proper adjustment, physical damage, or loose mounting. Verify switch plunger has proper travel and engagement with brake pedal arm (typically 0.5-1.0mm preload).
2
Step 2: Using a multimeter, backprobe the brake switch connector and verify continuity changes between open and closed states when brake pedal is pressed (should show open circuit at rest, closed circuit when pressed, or vice versa depending on switch type).
3
Step 3: Inspect wiring harness from brake switch to ABS module for chafing, pinching, or corrosion. Check connector terminals at both ends for bent pins, corrosion, or moisture intrusion. Measure resistance through circuit (should be less than 1 ohm).
4
Step 4: With ignition on and brake pedal at rest, measure voltage at brake switch connector (should be battery voltage or 5V reference depending on system design). Press brake pedal and verify voltage changes appropriately.
5
Step 5: If all external components test good, use advanced scan tool to monitor live ABS hydraulic pressure switch state while pressing brake pedal. Compare readings to manufacturer specifications for proper voltage range (typically 0.5-4.5V).
6
Step 6: Clear code, perform test drive with moderate braking, and verify repair. If code returns immediately without brake application, suspect internal ABS module or hydraulic unit failure.
Estimated Repair Cost
$100 - $1,200
Parts + labor, varies by vehicle and location
This code indicates the ABS control module has detected an electrical fault in the hydraulic brake pressure switch circuit. This switch monitors brake pedal application and hydraulic pressure within the ABS system to coordinate proper ABS operation. The control module detected either an open circuit...
The most common cause of C1103 (ABS Hydraulic Brake Switch Circuit Failure) is: Failed or misadjusted brake light/pressure switch at brake pedal assembly
Typical repair costs for C1103 range from $100 to $1,200, depending on the vehicle, location, and whether you do it yourself or go to a shop.
This is a critical safety issue as ABS functionality may be disabled or operate improperly, potentially causing loss of vehicle control during emergency braking situations. The vehicle may still have basic braking but without anti-lock capability. Repair should be performed immediately and aggressive driving should be avoided.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to C1103 to identify the root cause.
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Quick Info
Category
Chassis
System
Anti-lock Brake System (ABS)
Difficulty
Type
Manufacturer
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