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DTC codes / C06xx · Brakes, steering and suspension / C0618

C0618Park Brake Control Module Control Circuit High

The C0618 code indicates that the park brake control module has detected an abnormally high voltage on its control circuit, which typically points to an open circuit or a short to power rather than a short to ground. The module sets this code when the voltage on the circuit exceeds the expected range for normal operation, often disabling the electronic parking brake function as a result.

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

Symptoms you may notice

  • The parking brake warning light remains illuminated on the dashboard.
  • The electronic parking brake may fail to engage or release when the switch is operated.
  • A message such as 'Parking Brake Fault' or 'Service Parking Brake' appears on the driver information display.
  • The parking brake may apply automatically but not release, or vice versa, depending on the failure mode.
  • Often no symptoms besides the warning light, especially if the fault is intermittent.

Common causes, most likely first

  1. An open circuit in the park brake control module's power or ground circuit, such as a broken wire or loose connector.
  2. A short to voltage on the control circuit, often caused by chafed wiring contacting a power source.
  3. A faulty park brake control switch that sends an incorrect signal to the module.
  4. Corrosion or water intrusion in the connector at the park brake control module, leading to high resistance.
  5. A failed park brake control module itself, though this is less common than wiring issues.
  6. A blown fuse or relay in the park brake control circuit that interrupts power delivery.

How to diagnose and fix it

  1. Verify the battery voltage and ensure it is fully charged, as low voltage can cause false codes.
  2. Inspect the wiring harness and connectors at the park brake control module for damage, corrosion, or loose pins.
  3. Check the park brake control circuit for an open or short to power using a digital multimeter and wiring diagram.
  4. Test the park brake control switch for proper continuity and signal output.
  5. Check all fuses and relays related to the park brake system and replace any that are faulty.
  6. If wiring and components test good, substitute a known-good park brake control module to confirm the fault.
  7. Clear the code and perform a road test to verify the repair and ensure the code does not return.

Before you replace the park brake module

  • A common oversight is assuming the module is defective when the real problem is a chafed wire in the wheel well or underbody that shorts to a power source only during certain driving conditions.
  • The code can be set by a weak battery or charging system issue, so always load-test the battery and check charging voltage before diving into circuit diagnostics.
  • On some vehicles, the park brake control module shares a ground with other systems, and a poor ground can cause this code along with unrelated symptoms.
  • Intermittent C0618 codes often stem from a connector that is not fully seated or has corroded terminals, which can be missed during a quick visual inspection.
  • Do not overlook the park brake switch itself; a stuck or faulty switch can send a continuous high voltage signal that mimics a wiring short.

Can I keep driving with C0618?

If the parking brake warning light is on and the brake does not engage or release properly, avoid driving the vehicle because the parking brake may not hold on a slope or may drag and overheat. If the light is on but the brake operates normally, you can drive cautiously to a repair shop, but have the system inspected soon.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

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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