What it means
Park brake control module supply voltage above expected range. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the ABS or stability-control warning light
- The engine or gearbox may go into limp mode
How it works
The park brake control module depends on a stable supply voltage to operate and communicate with the braking and stability systems. C0618 sets when the module detects its supply above the expected range, which can happen if charging voltage is excessive or the supply circuit is being driven toward battery positive.
Common causes
Most likely first.
- Charging system overvoltage
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- ABS warning light on
- ESC/stability control deactivated
- Possible reduced brake assist
- Speedometer may behave erratically
How to diagnose it
- Scan all modules and save freeze-frame data, including system voltage and which brake or stability faults appeared with C0618.
- Check battery and charging-system operation against the manufacturer's specification to see whether overvoltage affects the whole vehicle.
- Inspect the park brake control module connector and supply wiring for moisture, corrosion, backed-out pins, chafing, or contact with a B+ source.
- With the fault present, monitor the module supply data while gently moving the harness to look for a voltage change or intermittent fault.
- Test the supply circuit for an unintended connection to battery positive and check connector contact condition using the manufacturer's procedure.
Common fixes
- Repair chafed or pinched supply wiring that contacts a B+ source.
- Clean or repair corroded connector terminals and restore proper pin fit.
- Repair the charging system if its output exceeds the manufacturer's specification.
- Replace a damaged connector or wire section that cannot maintain a sound connection.
Can I keep driving?
Because the fault can disable stability control and may affect brake assist, avoid high speeds, slippery roads, and towing until checked. If braking or steering assistance changes, stop safely and arrange help.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.