What does it mean?
OBD II fault code P06DE is a generic trouble code that is defined as P06DE – “Engine Oil Pressure Control Circuit Stuck On” or sometimes as P06DE – “Engine oil pressure control – control circuit malfunction – ON signal” and is set when the PCM (Powertrain Control Module) detects a defect or malfunction in the circuits that control and monitor the operation of a dual-pressure oil pump.
NOTE: Code P06DE may sometimes be present along with code P0520, with the latter code indicating a malfunction of or defect in the circuits of the oil pressure switch that monitors the actual engine oil pressure at all times, as opposed to a problem with the solenoid (and its associated wiring) that switches the oil pump between high and low-pressure modes. In most such cases, resolving code P0520 will usually, but not always, also resolve code P06DE.
Unlike older engines whose oil pumps delivered pressurized oil at a pressure that was determined by both the pumps’ capacity and the engine speed, most modern engines now have oil pumps that can be switched to pressurize engine oil to different levels to suit changing engine operating conditions.
Here is how this works in practice- The problem with old-style oil pumps is that although they deliver copious amounts of highly pressurized oil to moving engine parts at high engine speeds (when engines develop large amounts of power), the amount of energy an oil pump requires to force oil through small clearances between moving and sliding parts is relatively small compared to the engine’s total power output.
However, since old-style oil pumps deliver pressurized oil at fixed rates, the amount of energy an oil pump requires to pump oil around an engine that is running at low to moderate speeds remains the same, although the engine is now developing considerably less power. As might be expected, this greatly increases the total parasitic power loss an engine experiences, and while burning more fuel can overcome parasitic power losses, burning more fuel causes more harmful exhaust emissions.
So to remain within maximum allowable exhaust emission levels/limits, engineers developed oil pumps that deliver high-pressure oil at high engine speeds when engines require high levels of effective lubrication, and oil at a slightly lower pressure when engines are running at lower speeds and under light load conditions.
As a practical matter, the object of this oil pressure strategy s to reduce the parasitic power losses an engine experiences at low speeds to reduce exhaust emissions at low engine speeds since the engine no longer needs to burn more fuel to overcome high levels of parasitic power losses.
We need not delve into the technical complexities of how oil pumps vary their output beyond saying that in some designs, a control solenoid bleeds of excess oil pressure to reduce parasitic power losses, while in most other designs, various mechanisms change the pump’s interior geometry to either reduce or increase the pressure the pump develops. It should be noted that in both designs, the mechanisms that change the oil pump’s output is controlled directly by the PCM.
It should also be noted that to increase the lubrication system’s overall efficiency, most modern engines now use multiple oil pressure sensors that are located at different points around the engine to provide the PCM with an improved “big picture” sense of how efficiently (or otherwise) the engine is being lubricated at all times.
Nonetheless, while the advent of dual pressure (aka dual-stage oil pumps) has improved engine lubrication at low engine speeds while saving fuel at the same time, modern engine lubrication systems are highly complex systems that can go wrong for any number of reasons.
Regardless of the cause(s) of engine lubrication systems, though, most modern PCMs can detect a deviation from the desired oil pressure at almost any point in the lubrication system in about 250 microseconds (0.25 of a second) and in most cases, remedial action w