C1572

Code

FIAT C — Chassis

Load valve actuation time very high

Brand: FIAT

Type: C — Chassis

Views: UK: 15 EN: 20 RU: 11

AI status

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Page language: EN

Causes

Contaminated or degraded brake fluid causing valve sticking
Internal sticking or mechanical wear in the load/control valve
Electrical problem: open/short/wiring/connectors to valve or HCU
Insufficient supply voltage or poor ground at HCU
Air in the brake hydraulic system or low brake fluid level
Internal fault in HCU (solenoid driver or hydraulic body)

Symptoms

ABS/ESC/traction control warning light illuminated
Reduced or degraded ABS/ESP function during braking or cornering
Longer stopping distances or altered pedal feel
Occasional or constant DTC memory entries related to hydraulic control
Intermittent faults that may clear after ignition cycle or restart

What to check

Read and record all DTCs and freeze frame data with a compatible scan tool
Check battery voltage and charging system under load
Inspect HCU connectors and wiring for corrosion, breaks, or damage
Verify brake fluid level and condition; look for contamination or moisture
Monitor live data: valve command vs actual response time and status bits
Perform actuator/solenoid and HCU self-tests if available in diagnostic tool

Signal parameters

Valve actuation time (measured milliseconds) — should be within manufacturer threshold
Command signal (CAN/PWM) to HCU and corresponding valve command bit
Supply voltage at HCU during actuation (volts)
Solenoid coil resistance (ohms)
Actuator current draw during activation (amps)
Duty cycle or pulse width of command signal (if applicable)

Diagnostic algorithm

Connect a capable scanner, confirm C1572 and capture freeze frame/live data showing valve actuation time and related parameters.
Check battery/resting voltage and voltage during an actuation test; ensure proper supply and ground at HCU.
Visually inspect HCU connectors, wiring harness, and pins; repair any corrosion, breaks, or loose pins.
Check brake fluid level and condition; if contaminated, flush and replace fluid before further tests.
If service manual allows, perform a commanded solenoid/valve activation via diagnostic tool while monitoring voltage, current and actuation time.
Measure solenoid coil resistance and compare to factory specification; abnormal values indicate open/shorted coil.
If actuation time remains high, perform hydraulic checks: bleed system, check for internal valve sticking or debris in valve body. Consider bench testing or removing HCU for inspection if skilled and following safety procedures.
If hydraulic/mechanical causes are ruled out but electrical driving signals are correct, suspect internal HCU driver fault and consider module replacement or refurbishment.
After repairs, clear codes and perform road test/actuation cycles to confirm normal valve actuation time and absence of recurrence.

Likely causes

Valve spool contaminated or seized due to dirty fluid
Solenoid coil partially open or high resistance causing slow response
Poor connector contact or corroded terminal at actuator
Low battery/weak charging system reducing actuation speed
Internal hydraulic leak or worn valve seals
Faulty HCU driver circuitry

Fault status

⚠️ Status

Load valve actuation time exceeds allowed threshold. Hydraulic valve response slow or unresponsive — may limit ABS/ESP functionality and trigger warning lamp(s).

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.5 - 3.0 hours

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