Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
C1604 ECU Hardware Error: General Description
The HECU consists of an ECU (Electronic Control Unit) and a HCU(Hydraulic Control Unit).
The HCU portion of the assembly contains a pump motor, solenoid valves, and accumulator.
Increase and decrease of hydraulic pressure is operated by electronic motor, according to a measured signal by wheel speed sensor.
The function of HCU is to increase, decrease or maintain the hydraulic pressure supplied to a wheel cylinder by operating return pump according to HECU control signal while ABS control is active.
The ECU monitors various sensor and switch inputs.
These inputs are used to make decisions regarding HCU component operation.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.