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DTC codes / C06xx · Brakes, steering and suspension / C0660

C0660Park Brake Switch Circuit

The C0660 code indicates that the electronic brake control module (EBCM) has detected a fault in the park brake switch circuit, which is the electrical path that tells the module whether the parking brake is engaged or released. The module monitors voltage or continuity on this circuit and sets the code when the signal falls outside the expected range for the current ignition state and vehicle speed.

SystemChassis
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaBrakes, steering and suspension

Symptoms you may notice

  • The red brake warning light on the instrument cluster stays illuminated or flashes intermittently.
  • The parking brake may appear to be applied when it is actually released, or the release warning may not extinguish after lowering the lever.
  • Cruise control may fail to engage or may disengage unexpectedly if the vehicle uses the park brake signal as a safety interlock.
  • A chime or message may appear on the driver information center stating the parking brake is engaged.
  • Often no symptoms besides the warning light, especially if the switch signal is only intermittently out of range.
  • Electronic parking brake systems may refuse to release automatically or may require manual override.

Common causes, most likely first

  1. A faulty park brake switch that has worn contacts or a broken internal mechanism.
  2. Corroded, loose, or damaged electrical connector at the park brake switch or at the electronic brake control module.
  3. An open or shorted wire in the park brake switch circuit, often caused by chafing or rodent damage.
  4. A misadjusted park brake switch that does not fully change state when the lever is moved.
  5. Water intrusion into the switch or connector, leading to intermittent continuity.
  6. A failed electronic brake control module, though this is less common and should be confirmed after all circuit tests pass.

How to diagnose and fix it

  1. Verify the park brake switch operates correctly by watching live data for the park brake status parameter while cycling the lever by hand.
  2. Inspect the switch connector and the electronic brake control module connector for corrosion, loose pins, or water intrusion, and clean or repair as needed.
  3. Test the park brake switch circuit for continuity and short-to-ground or short-to-voltage faults using a digital multimeter, following the manufacturer's wiring diagram.
  4. Check the switch adjustment and the lever mechanism to ensure the switch plunger or contact is fully actuated and released through the full travel.
  5. If the switch tests out of specification, replace the park brake switch and clear the code to see if it returns.
  6. If the circuit and switch are good, perform a wiggle test on the harness while monitoring live data to expose an intermittent wiring fault.
  7. As a last step, after all other possibilities are eliminated, substitute a known-good electronic brake control module or follow the manufacturer's diagnostic flow for module replacement.

Before you replace the park brake switch

  • A common mistake is replacing the park brake switch without checking the switch adjustment; a switch that is slightly out of adjustment can set C0660 even though the switch itself is electrically sound.
  • The park brake switch circuit often shares a ground or reference voltage with other switches, so a fault in a related circuit can set C0660 as a secondary code and mislead diagnosis.
  • Intermittent C0660 codes are frequently caused by a chafed wire near the park brake pedal assembly or lever, where movement over time wears through insulation.
  • Some vehicles use the park brake switch signal for the automatic parking brake release and for cruise control inhibit, so a failing switch can cause drivability complaints that seem unrelated to the brake system.
  • A scan tool that can read live park brake switch status is far more useful than a code reader alone, because it lets you watch the signal change as you operate the lever and catch intermittent faults.

Can I keep driving with C0660?

The vehicle remains safe to drive because the service brakes are unaffected, but you should avoid relying on the parking brake until the fault is repaired, and be aware that cruise control or automatic parking brake functions may not work. If the warning light is accompanied by a message that the parking brake is engaged, verify manually that the brake is fully released before driving.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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