P0574
Cruise Control/Brake Switch A Circuit High
Powertrain Chassis/Safety Cruise Control Circuit 🟡 Moderate — Fix within a week
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What This Actually Means
In plain language — no jargon

The cruise control brake switch circuit is stuck in a high voltage state, like a light switch that's permanently flipped on instead of toggling. The ECU expects this signal to toggle between high and low when you press the brake, but it's not doing that.

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Symptoms You May Notice
3 known symptoms for this code
Cruise control won't engage or randomly disengages
Brake lights may stay on or behave erratically
Check Engine light illuminated
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Embedded Systems Insight
What the ECU/ECM is actually computing

The ECU monitors the brake switch circuit voltage to detect when the brake pedal is pressed. The circuit should toggle between low voltage (brake pressed) and high voltage (brake released). When the voltage remains stuck high, the ECU cannot properly detect brake application and disables cruise control for safety.

Voltage & Parameter Thresholds

Parameter Normal Range Fault Condition
Brake Switch Voltage 0.5V (pressed) to 4.5V (released), toggling on pedal input Constant 4.5V+ with no toggling or response to brake pedal
Circuit Response Time Voltage change within 100ms of pedal press No voltage change detected or delayed response
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Diagnostic & DIY Fix Guide
Check these in order — from cheapest to most complex
1
Brake switch connector
Inspect and reseat the brake switch electrical connector under the dashboard near the brake pedal for corrosion or loose terminals.
2
Brake switch assembly
Replace the brake switch if connector is clean but fault persists; they commonly fail by sticking in the open position.
3
Cruise control wiring harness
Check the wiring between the brake switch and ECU for damaged insulation or shorts that keep the circuit voltage high.