What does it mean?
C1284 is a Chassis (ABS, traction control, steering) fault code. It indicates: Oil Pressure Switch Failure . This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
Symptoms
- Warning lamp and a system message for the hydraulic circuit concerned
- Heavy steering or a hard brake pedal when the pressure loss is real
- Pump noise, especially at idle or during a manoeuvre
- Visible leak or a low fluid level in the reservoir
- Switch state in live data does not change while the system builds pressure
- Loss of assist can appear suddenly, so the vehicle should be driven with care until repaired
Likely causes
- Pressure switch stuck open or closed, or contacts worn inside the switch
- Open, shorted or corroded wiring in the switch circuit
- Low fluid level or genuine low system pressure so the switch never changes state
- Leaking pump, hose or seal in the hydraulic circuit the switch monitors
- Restricted or blocked line so pressure never reaches the switch
- Loose connector or a damaged terminal at the switch
- Control module input circuit fault
How to fix it
- Check the fluid level and look for leaks before starting any electrical test
- Read the switch state in live data at rest and again with the system pressurised
- Unplug the switch and test the circuit for open, short to ground and short to voltage
- Test the switch itself for a clean continuity change when pressure is applied
- Measure actual system pressure with a gauge where a test port exists, to separate a real pressure loss from a switch fault
- Repair the harness or replace the switch, and address the pump or restriction if pressure is genuinely low
- Bleed and refill the system after any hydraulic repair, then confirm the code stays cleared