P253F – Engine oil deteriorated

By Reinier (Contact Me)
Last Updated 2019-05-09
Automobile Repair Shop Owner

Table of Contents

1. What Does Code P253F Mean?
2. Where is the P253F sensor located?
3. What are the common causes of code P253F?
4. What are the symptoms of code P253F?
5. Get Help with P253F

What Does Code P253F Mean?

OBD II fault code P253F is a generic code that is defined as “Engine Oil Deteriorated”, and is set when the PCM (Powertrain Control Module) detects that either the engine oil change interval had been exceeded, or that the quality of the engine oil had deteriorated to the point where it must be replaced.

On applications that are equipped with engine oil life monitoring systems, the PCM uses various strategies and parameters to determine the remaining useful life of the engine oil. Typically, the least complex systems merely count the days since the last oil change and counter reset. While these oil-monitoring systems also take into account the distance traveled since the last oil change, it should be noted that simple counter-based systems cannot determine the actual degree of oil degradation.

Slightly more complex systems on the other hand, typically use information such as the number of engine starts, as well as other parameters including the total distance traveled, the average ambient temperature and humidity, average engine load, and the number of times the engine operated under WOT (wide Open Throttle) conditions since the last oil change.

The most complex oil monitoring systems use all of the above parameters, as well as the number of DPF (Diesel Particulate Filter) regenerations, average catalytic converter efficiencies, and even average turbocharger boost pressures in conjunction with a dedicated sensor, whose function it is to monitor the electrical conductivity of the engine oil as a function of the presence of various contaminants in the oil.

As a practical matter though, the rate at which engine oil deteriorates or degrades depends on many factors, not the least of which is the effect of oxidation of the oil, and the effect of high engine temperatures on the additives in the oil. Following close behind is the combined effects of corrosive acids that form naturally as the result of oxidization of the oil, and the effect of oil dilution by unburned fuel that seeps into the oil.

We need not delve into the complexities of engine oil chemistry here, but lubrication engineers are now able to use the parameters and conditions described above to predict the rate at which engine lubricants degrade fairly accurately. Thus, since the rate of oil degradation can be predicted, it became possible to develop algorithms that use many parameters to calculate the remaining useful life of engine oil.

However, it must be noted that although oil-monitoring systems are based on complex algorithmic calculations, no oil monitoring system in use today can account for all possible variations of vehicle use, or for all variations in environmental conditions, and/or for variations between different brands of engine oil. In translation, this means that even though two identical vehicles may use the same brand, grade, and formulation of engine oil, differences in climatic/environmental conditions, vehicle use, driving style, fuel quality, and the frequency of routine servicing can produce vastly different rates of oil degradation.

Be aware however that all major car manufacturers go to some lengths to point out in their user manuals that an over reliance on oil quality monitoring systems could void a vehicles’ warranty, simply because no oil monitoring system can account for all variables on all applications. For instance, if one driver always drives aggressively with large throttle openings over short distances that do not allow the engine and exhaust system to warm up to optimum temperatures, the oil in that vehicles’ engine will degrade a lot faster than it would in an identical vehicle that is used only on long trips during which large throttle openings are rarely used. In practice, the oil in the second vehicle will not degrade as fast, and as a result, the oil monitoring system may not “recommend” an oil change within the oil change interval specified by the vehicle manufacturer. Therefore, all major vehicle manufacturers recommend that the engine oil be changed at least once a year, regardless of the distance traveled, or the fact that the oil monitoring system may not have recommended an oil change within the specified oil change interval.

Nonetheless, when the PCM detects or determines that the engine oil has no, or little useful life remaining, it will set code P253F, illuminate a warning light, and/or display a warning message on the dashboard. Note that while false positive instances of code P253F are not unknown, ignoring the presence of the code and its associated warning(s) could result in engine failure, and almost certainly in the vehicle’s warranty being voided.

Where is the P253F sensor located?

The image above is an example of the type of warning massage that may be displayed when the engine oil is deemed to have degraded to an unacceptable degree. Note though that on some applications, there may not be an explicit reference to the quality of the engine oil; in these cases, the oil pressure warning light may illuminate, and a message such as “SERVICE ENGINE SOON” may be displayed.

What are the common causes of code P253F?

Note that while some causes of code P253F depend on both the application and the complexity of the oil monitoring system, typical causes of this code could one or more of the following-

• Oil change interval exceeded
• Excessively degraded oil due to an episode of engine overheating
• Poor fuel quality
• Use of incorrect or unsuitable oil
• The presence of contaminants such as excessive amounts of metal wear particles, engine coolant, unburned fuel, or water in the oil
• Failure to complete an oil monitor resetting procedure
• Improper resetting procedure of the oil monitor system during a previous or current oil change
• Defective oil quality sensor (if fitted)
• Failed or failing PCM, but note that since this is a rare event, the fault must be sought elsewhere before any control module is replaced

What are the symptoms of code P253F?

This code will typically not produce drivability issues, or any symptoms other than a stored trouble code, illuminated warning light, and/or a displayed warning message.

However, depending on both the application and the nature of the problem, other codes could be stored along with P253F, which codes would typically relate to fuel and cooling system issues.

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