Code
C1094
ALFA ROMEO
C — Chassis
Right rear discharge valve
Views:
UK: 6
EN: 17
RU: 10
AI status
Completed
Completed
100%
Causes
- Open or shorted wiring to right‑rear discharge valve
- Poor connector contact or corrosion at valve or ABS module connector
- Faulty right‑rear discharge (solenoid) valve
- Faulty ABS/ESC control module or internal driver circuit
- Related fuse, relay or power supply fault
- Mechanical seizure or hydraulic blockage in valve body
Symptoms
- ABS/ESC warning lamp illuminated on dash
- Reduced ABS/traction control function; possible ABS active not available
- Abnormal brake feel during ABS operation or pulsation
- Brake stability/traction control interventions may be incorrect or absent
- Diagnostic trouble code(s) stored; related ABS faults may also be present
What to check
- Retrieve full ABS fault list and freeze frame with a factory‑level scan tool
- Visually inspect wiring and connector at right‑rear valve and ABS hydraulic unit for damage, corrosion, or loose pins
- Check battery voltage and ground connections before testing (stable >12V)
- Check relevant fuses and relays powering ABS hydraulic unit
- Measure coil resistance of the right‑rear discharge valve at the valve connector (compare to spec)
- Backprobe valve control circuit at the ABS module while operating ABS tests with scan tool; check for control pulses and proper supply voltage
Signal parameters
- Typical valve coil resistance: commonly in the low ohms to tens of ohms range (e.g., ~5–30 Ω) — consult vehicle‑specific spec
- Control signal: PWM switching from the ABS module; amplitude usually 0–12 V (battery referenced) with variable duty cycle during modulation
- Idle/standby: valve circuit may be held to supply or ground depending on system design; monitor for steady voltage or pulsed waveform while commanding valve
- Expected actuator current: pulses up to ~1–3 A depending on design — use clamp meter/oscilloscope when checking
Diagnostic algorithm
- Connect a capable ABS scan tool, read and record all ABS/ESC codes and freeze frame data; clear codes and attempt re‑creation.
- Visually inspect valve harness and connectors (right‑rear). Repair any obvious damage before further testing.
- Confirm battery voltage and good chassis/engine ground. Low voltage can cause spurious faults.
- With ignition on, measure supply voltage at the valve connector; verify reference power and ground presence per wiring diagram.
- Measure coil resistance at the valve connector (apply manufacturer spec). An open or shorted coil indicates valve replacement.
- Command the right‑rear discharge valve using an active test from the scan tool while backprobing the control line at the ABS module and at the valve; observe voltage waveform and current draw with oscilloscope/ammeter.
- If electrical control is present at the module but not at the valve, inspect wiring between module and valve (repair open/short). If control is absent at the module, suspect ABS module driver fault and continue module diagnosis per factory procedure.
- If valve is electrically good but hydraulic operation is suspect, replace or rebuild ABS hydraulic unit/valve block and bleed system per service manual. After repairs, clear codes and perform road test and ABS functional test.
- If module replacement is required, follow manufacturer programming/relearn/adaptation procedures as specified.
Likely causes
- Damaged wiring harness or chafed insulation to right‑rear valve
- Corroded/loose connector at the valve or ABS module
- Failed discharge solenoid (valve coil short/open)
- Faulty hydraulic control unit (ABS pump/valve assembly)
Fault status
Status
Fault detected in right‑rear discharge valve circuit — ABS/ESC control limited until repaired.
Repair difficulty: Medium
Diagnostic time: 1.5-3.0 hours
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