What Does C1127 Mean?
This code indicates the cruise control module has detected a circuit failure in the cruise control deactivator brake switch circuit. The brake switch provides a critical signal to the cruise control system to disengage cruise when the brake pedal is pressed. This is a safety-critical circuit that ensures the driver can always override cruise control by braking.
Common Causes
35%
Failed brake light/deactivator switch mounted at the brake pedal bracket, often from internal contact wear
25%
Misadjusted brake switch that has lost contact with the brake pedal arm due to worn bumper pad or switch clip
20%
Corroded or damaged wiring between the brake switch and the cruise control module
15%
Loose or corroded connector at the brake switch preventing reliable electrical contact
5%
Cruise control module internal failure on the brake switch input
Diagnostic Steps
1
Step 1: Verify brake lights are functioning properly. If brake lights do not work either, the issue is likely the brake switch itself. Check for the brake pedal bumper pad — a missing pad causes the switch to be over-extended.
2
Step 2: Disconnect the brake switch connector and measure continuity across the cruise control deactivator terminals while manually pressing and releasing the switch plunger. The switch should toggle between open and closed cleanly.
3
Step 3: With the switch connected, backprobe the cruise deactivator signal wire at the cruise control module and verify proper voltage change when the brake pedal is pressed (typically 12V to 0V or vice versa).
4
Step 4: Check wiring continuity from the brake switch connector to the cruise control module. Test for opens, shorts to ground, and shorts to battery.
5
Step 5: Clear codes, test drive, and verify cruise control engages and properly disengages when the brake pedal is pressed.
Estimated Repair Cost
$30 - $200
Parts + labor, varies by vehicle and location
This code indicates the cruise control module has detected a circuit failure in the cruise control deactivator brake switch circuit. The brake switch provides a critical signal to the cruise control system to disengage cruise when the brake pedal is pressed. This is a safety-critical circuit that en...
The most common cause of C1127 (Cruise Control Deactivator Brake Switch Circuit Failure) is: Failed brake light/deactivator switch mounted at the brake pedal bracket, often from internal contact wear
Typical repair costs for C1127 range from $30 to $200, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Cruise control is disabled as a safety precaution. If the brake switch has completely failed, brake lights may also be inoperative, which is a significant safety hazard. Verify brake light operation immediately.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to C1127 to identify the root cause.
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Quick Info
Category
Chassis
System
Cruise Control System / Brake Signal Circuit
Difficulty
Type
Manufacturer
Recommended Tools
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