C0122 is a chassis/ABS diagnostic trouble code used on applicable vehicles to identify a problem involving the front inlet solenoid valve on the right-hand side of the ABS hydraulic control system.
On vehicles such as applicable Subaru models, C0122 can indicate a malfunction of the front right ABS inlet solenoid valve inside the ABS control module and hydraulic control unit. The exact definition and diagnostic procedure can vary by manufacturer and model year.
The ABS module monitors the electrical and operating condition of the solenoid valve. If the detected condition is outside the expected range, the ABS module can store C0122.
Fault Code Description
C0122 = Front Inlet Solenoid Valve Right Malfunction on applicable ABS systems.
The front inlet solenoid valve is part of the hydraulic control system used by the ABS module to regulate brake fluid pressure at the wheel during ABS operation.
C0122 does not automatically mean that the complete ABS hydraulic unit has failed. Wiring, connectors, solenoid resistance, power supply, internal hydraulic-unit faults, or the ABS control module can also be involved.
What Does C0122 Mean?
C0122 means that the ABS control system has detected a malfunction associated with the front right inlet solenoid valve.
The valve is used to control hydraulic brake pressure during ABS operation. When the ABS module detects an abnormal electrical or functional condition, it may disable part or all of the ABS system and store C0122.
Because C0122 is manufacturer-dependent, the exact component description should always be confirmed using the vehicle-specific service information.
C0122 ABS System Operation
During ABS operation, the ABS control module commands hydraulic solenoid valves to regulate brake pressure. The inlet valve controls the flow of brake fluid into the corresponding hydraulic circuit.
Symptoms of C0122
- ABS warning light.
- Brake warning light on some vehicles.
- Traction control warning light.
- Electronic stability control warning light.
- ABS system may become disabled.
- EBD function may be disabled on applicable systems.
- Additional ABS fault codes.
- ABS may not activate correctly during hard braking.
- Possible changes in brake pressure control.
The exact symptoms depend on the vehicle and ABS system architecture.
Common Causes of C0122
- Faulty front right ABS inlet solenoid valve.
- Open solenoid valve circuit.
- Shorted solenoid valve circuit.
- Damaged ABS wiring harness.
- Corroded electrical connector.
- Loose or damaged connector terminals.
- Incorrect solenoid resistance.
- Poor ABS module power supply.
- Poor electrical ground.
- Internal hydraulic control unit fault.
- ABS control module fault.
- Water or contamination inside the connector.
How to Diagnose C0122
1. Scan the ABS Module
Use an ABS-capable scan tool to confirm C0122 and check for additional ABS, wheel-speed sensor, hydraulic, or communication codes.
Record the stored codes and freeze-frame information when available before clearing the fault memory.
2. Check ABS Power and Ground
Verify the ABS control module has the correct battery power supply and ground. A low-voltage or poor-ground condition can create abnormal ABS valve faults.
3. Inspect the ABS Connector
Inspect the ABS hydraulic-control-unit connector for corrosion, water intrusion, damaged terminals, loose connections, or signs of overheating.
4. Inspect the Solenoid Valve Circuit
Using the vehicle-specific wiring diagram, identify the circuit for the front right inlet solenoid valve.
Check the circuit for an open circuit, short circuit, excessive resistance, damaged insulation, or poor terminal contact.
5. Check Solenoid Resistance
Measure the resistance of the applicable inlet solenoid valve according to the manufacturer's test procedure.
Do not assume that one resistance value applies to every vehicle. Compare the measurement with the correct manufacturer specification.
6. Check the ABS Hydraulic Unit
If the wiring and electrical connections are correct but the solenoid valve does not respond according to the manufacturer's test procedure, the hydraulic control unit may require further testing.
7. Check the ABS Control Module
An internal ABS module or hydraulic-control-unit fault should only be considered after power, ground, wiring, connector and solenoid tests have passed.
C0122 Diagnostic Signal Flow
C0122 Electrical Testing
Electrical testing should be performed using the correct wiring diagram for the vehicle. The technician should identify the solenoid power circuit, control circuit, ground path and ABS module terminals before testing.
- Check battery voltage.
- Check ABS fuses.
- Check ABS module power.
- Check ABS module ground.
- Inspect the hydraulic-unit connector.
- Check solenoid resistance.
- Check wiring continuity.
- Check for short circuits.
- Perform voltage-drop testing where appropriate.
- Compare measurements with manufacturer specifications.
Is C0122 Serious?
C0122 should be treated as an important ABS fault.
A malfunctioning ABS inlet solenoid can affect the ability of the ABS system to control hydraulic brake pressure correctly during emergency braking.
On some systems, the ABS module may also disable EBD, traction control, or stability-control functions when this type of fault is detected.
Can I Drive With C0122?
Driving should be minimized until the ABS fault is diagnosed.
The conventional hydraulic brakes may still operate on some vehicles, but ABS and related electronic braking functions may not be available.
If the brake pedal feels abnormal, braking performance is reduced, or a red brake warning light is illuminated, the vehicle should not be driven until it has been inspected.
C0122 Repair
The correct repair depends on the confirmed cause of the fault.
- Repair damaged wiring.
- Repair an open solenoid circuit.
- Repair a shorted circuit.
- Repair loose or damaged terminals.
- Clean or replace corroded connectors.
- Repair ABS power or ground problems.
- Replace the affected solenoid where separately serviceable.
- Repair or replace the hydraulic control unit when confirmed faulty.
- Repair or replace the ABS control module when an internal failure is confirmed.
Common Repair Mistakes
Replacing the ABS Module Immediately
Do not replace the ABS module simply because C0122 is stored. Test the wiring, connector, power supply, ground and solenoid circuit first.
Replacing the Hydraulic Unit Without Testing
A damaged connector or open circuit can produce symptoms similar to an internal hydraulic-unit fault.
Using the Wrong Solenoid Specification
Solenoid resistance and control strategies vary between ABS systems. Always use the manufacturer-specific specification.
Ignoring Other ABS Codes
C0122 may appear together with other ABS codes. Diagnose related codes first when the manufacturer diagnostic procedure indicates that they are connected.
Related ABS Codes
- C0120 – Front Inlet Solenoid Valve LH Malfunction on applicable systems.
- C0121 – Front Outlet Solenoid Valve LH Malfunction on applicable systems.
- C0122 – Front Inlet Solenoid Valve RH Malfunction on applicable systems.
- C0123 – Front Outlet Solenoid Valve RH Malfunction on applicable systems.
- C0124 – Rear Inlet Solenoid Valve LH Malfunction on applicable systems.
- C0126 – Rear Inlet Solenoid Valve RH Malfunction on applicable systems.
FAQ About C0122
What does C0122 mean?
C0122 is an ABS/chassis diagnostic trouble code. On applicable systems, it indicates a malfunction involving the front right inlet solenoid valve. The exact definition depends on the vehicle manufacturer.
What causes C0122?
Possible causes include a faulty inlet solenoid valve, open or shorted wiring, poor electrical connections, damaged terminals, poor ABS power or ground, or an internal ABS hydraulic-unit fault.
Is C0122 an ABS code?
Yes. C0122 is a chassis-related code associated with the ABS system on applicable vehicles.
Can a bad ABS solenoid cause C0122?
Yes. A defective front right inlet solenoid can cause C0122 on systems that use this definition. However, the solenoid circuit and connector should also be tested before replacing the component.
Can I drive with C0122?
Driving should be minimized until the ABS system is diagnosed because ABS and related electronic braking functions may be unavailable.
Does C0122 mean the ABS module is bad?
Not necessarily. Wiring, connectors, power, grounds and the solenoid valve should be tested before condemning the ABS control module.
What should I check first for C0122?
Start by scanning the ABS module, checking ABS power and ground, inspecting the hydraulic-unit connector, and testing the front right inlet solenoid circuit according to the manufacturer's specifications.
Final Result
C0122 is an ABS/chassis-related diagnostic trouble code that can indicate a front right inlet solenoid valve malfunction on applicable vehicles.
The most reliable diagnosis is to inspect the ABS power supply, grounds, connector, wiring and solenoid circuit before replacing the hydraulic unit or ABS control module.
Because C0122 is manufacturer-dependent, always verify the exact code definition, component location, connector pinout, resistance specification and diagnostic procedure for the specific vehicle.