What does it mean?
P1189 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Engine Oil Pressure Switch Circuit Malfunction .
Symptoms
- Check engine light on, sometimes with an oil pressure warning that comes and goes
- Oil pressure warning lamp stays on with the engine running, or never lights during the bulb check
- Oil pressure display on the instrument cluster reads implausibly
- Systems that depend on oil pressure, such as variable valve timing or start-stop, may be limited
- Ticking or knocking from the valve train if the pressure really is low
- No driveability change at all when the fault is purely electrical
Likely causes
- Failed oil pressure switch with contacts stuck open or closed
- Oil leaking into the switch body and wetting the connector, a common failure on older switches
- Broken, chafed or shorted wire between the switch and the module or gauge circuit
- Corroded connector or a loose terminal at the switch
- Genuinely low oil pressure from low oil level, a worn pump or a blocked pick-up screen
- Wrong oil viscosity or badly degraded oil affecting real pressure
- Rarely, a module or instrument cluster input fault
How to fix it
- Check the oil level and condition first; top up or change the oil if it is low, thin or overdue
- Fit a mechanical gauge in place of the switch and measure real pressure at idle and at raised engine speed against specification
- Compare the switch state in live data with the mechanical gauge to see whether the switch reports correctly
- Inspect the switch and its connector for oil leakage, corrosion and loose terminals
- Test the switch wire for continuity to the module and for a short to ground
- Replace the oil pressure switch if real pressure is correct but the reported state is wrong
- Investigate the pump, pick-up screen and relief valve if the measured pressure is genuinely low