Cruise Control Deactivation Switch Circuit Failure
The C1127 code indicates that the Powertrain Control Module (PCM) has detected a fault in the cruise control deactivation switch circuit, which is often integrated with the brake pedal position (BPP) switch. The PCM monitors the voltage signal from this switch to disengage cruise control when the brake is applied. A signal that is out of range, shorted to ground, shorted to battery voltage, or an open circuit will trigger this diagnostic trouble code (DTC).
1. Commonly Affected Makes
2. Most Common Causes
- Faulty brake pedal position (BPP) switch or cruise control deactivation switch
- Open, short-to-ground, or short-to-voltage in the switch signal circuit wiring
- Damaged, corroded, or loose connector terminals at the switch
- Blown fuse in the switch power supply circuit (if applicable)
- Internal PCM failure (rare)
3. Symptoms You Will Notice
- Cruise control inoperative or does not disengage when braking
- Check Engine Light or cruise control indicator illuminated
4. Step-by-Step Diagnosis
Scan for additional codes and verify C1127 is present.
Inspect the brake pedal position switch and cruise control deactivation switch for proper operation and adjustment.
Check the switch signal circuit for opens, shorts to ground, or shorts to voltage using a multimeter.
Inspect connectors for corrosion, damage, or loose terminals; clean or repair as needed.
Check the relevant fuse in the switch power circuit.
If all else fails, test the PCM for proper signal reception and consider PCM replacement as a last resort.
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, it is generally safe to drive, but cruise control may not function or may not disengage properly. Have the issue diagnosed and repaired soon to ensure safe operation.
How much does it cost to fix?▼
Repair costs typically range from $100 to $300, depending on whether the switch needs replacement, wiring repairs, or diagnostics. PCM replacement, if needed, can cost significantly more.