Cause
Stuck oil pressure relief valve
The relief valve limiting maximum oil pressure, stuck so it can no longer regulate. It is a simple spring-loaded valve whose job is to dump surplus oil back to the sump once pressure reaches its limit, and it fails in both directions.
Stuck open is the dangerous one: oil bypasses continuously and pressure never builds, which reads exactly like a worn pump or worn bearings. A sudden loss of pressure on an engine with no history of wear is worth taking to the relief valve first, since it is a fraction of the cost of the alternatives.
Stuck closed gives excessive pressure, which stresses the filter and seals and can blow a filter's seam or push oil past a crankshaft seal. Debris is the usual mechanism — a particle holding the valve off its seat — so a stuck valve means the oil is dirty, and it is worth inspecting the sump. Confirm pressure with a mechanical gauge before concluding anything, since the sensor is the other explanation.
Typically specialist work. Needs equipment or training most home workshops do not have.
Some of these codes mean you should stop driving
1 of the 2 codes this can cause indicate a fault where continuing to drive risks damage or is unsafe. Which one you have matters more than the cause does — read the code's own page before deciding.
Codes this can cause (2)
Codes where this is a likely explanation first, rather than merely a possible one.
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