|Trouble Code||Fault Location||Probable Cause|
|P0520||Engine oil pressure sensor/switch -circuit malfunction||Wiring, engine oil pressure sensor/switch, ECM|
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What Does Code P0520 Mean?
OBD II fault code P0520 is a generic code that is defined as “Engine oil pressure sensor/switch -circuit malfunction”, and is set when the PCM (Powertrain Control Module) detects either an actual low oil pressure condition, or a malfunction in the oil pressure switch and/or its control circuit.
On most applications, the oil pressure switch is a simple pressure switch that is fed with a reference voltage by the PCM. The pressure-sensing mechanism in the switch is in direct contact with the oil circulating through the engine, and since changes in oil pressure produce either a decrease or increase in the oil pressure switch’s resistance, the PCM is able to “convert” the changes in resistance into a reasonably accurate representation of the actual oil pressure at any given moment and engine speed.
In practice, the PCM in any given application is programmed to recognize a range of signal voltages (that roughly correspond to actual oil pressure(s)) that represent the acceptable oil pressure range for that application. Thus, when the PCM detects either an abnormally high or low signal voltage, that by extension could indicate an abnormal oil pressure, it will set code P0520, and illuminate a warning light.
Non-professional mechanics should also take note that some applications employ more than one oil pressure switch. As a rule, these applications use one sensor to indicate high, or normal, pressure conditions, and another to indicate low-pressure conditions. The two switches are NOT interchangeable, which is why they are always differentiated by color, or some other clearly identifiable characteristic. Refer to the manual for the application to determine the number, location, appearance [of the oil pressure switches], and the operating principles of lubrication systems that use more than one oil pressure sensor/switch.
NOTE: When code P0520 occurs on some applications, the PCM may set also set code P2105 – “Throttle Actuator Control System – Forced Engine Shutdown”, which means that the PCM has initiated a forced shutting down of the engine to protect the engine. Be aware that when codes P0520 and P2105 appear together, it may not be possible to restart the engine until code P0520 has been resolved.
The image below shows a much-simplified schematic of a typical oil pressure switch. Note however, that while this example is a simple ON-OFF switch, other designs employ oil pressure-driven potentiometers to supply a more accurate representation of the actual oil pressure in the lubrication system. Refer to the manual for the application being worked on for detailed information on the location, and operating principles of the oil pressure switch on that application.
What are the common causes of code P0520 ?
Some typical causes of P0520 could include the following-
- Defective oil pressure switch
- Damaged, burnt, shorted, disconnected, or corroded wiring and/or connectors
- Use of unsuitable engine oil
- Poor basic preventive maintenance, such a failure to change the oil and oil filter regularly
- Excessive mechanical wear in the engine
- Mechanical failure of internal engine components such as (among others), the oil pump, oil pressure relief valve, or even timing chain tensioners and/or guides
- Failed or failing PCM. Note that this is an exceedingly rare event in instances of P0520, and the fault must therefore be sought elsewhere before the controller is replaced.
What are the symptoms of code P0520 ?
Typical symptoms of code P0520 could include the following-
- Stored trouble code(s), and an illuminated warning light
- Engine may be shut down by the PCM. If this happens, code P2105 will almost certainly be present.
- Depending on the application and the nature of the problem, there may be various mechanical noises present when the engine is running. Noises could include ticking, thudding, knocking, or rumbling sounds that change as the engine speed changes.
- Depending on the application and the nature of the problem, the engine may misfire, especially if the problem is an actual low oil pressure condition that interferes with, or prevents the correct operation of hydraulic valve lifters
How do you troubleshoot code P0520 ?
SPECIAL NOTES: Non-professional mechanics should take note that a malfunction in the oil pressure switch’s control circuit can mimic a low oil pressure condition, and vice versa, but since the PCM cannot always differentiate between the two conditions, the actual oil pressure MUST be tested independently of the operation/serviceability of the oil pressure switch and its control circuit to verify that both the oil pressure switch, and its control circuit are working properly.
Note that on some applications, the oil pressure gauge in the dashboard is also electronically operated; which means that oil pressure gauges of this type can NOT be used to verify that the actual oil pressure at given moment falls within acceptable limits. Always use a separate and dedicated pressure gauge (that attaches to the engine where the oil pressure switch is screwed in) to verify that the oil pressure falls within the specified range. END OF SPECIAL NOTES.
Assuming that there are no mechanical noises present when the engine is running, record all fault codes present, as well as all available freeze frame data. This information can be of use should an intermittent fault be diagnosed later on.
NOTE #1: Also, use this opportunity to verify that the oil level is up to its proper mark, and to check that the oil is not diluted with fuel or engine coolant, or that it does not have a thick, tarry consistency. Top off the oil level if required, or investigate and correct all other conditions mentioned here before proceeding with the diagnostic/repair procedure.
NOTE #2: Be aware that not all mechanical noises mean that the engine is ruined. In many cases, such as when a low oil level or low oil pressure condition prevents the correct operation of hydraulic valve lifters, the ticking noise will go away when the problem is resolved.
Refer to the manual for the application to locate all the oil pressure switches on the engine, as well as the routing, location, function, and color-coding of all associated wiring. Perform a thorough visual inspection of all wiring, and look for damaged, burnt, disconnected, shorted, or corroded wiring and/or connectors. Make repairs as required, clear all codes, and rescan the system to see if the code returns.
If the code persists, prepare to perform resistance, reference voltage, and continuity checks on all associated wiring. Compare all obtained readings with the values stated in the manual, and make repairs as required to ensure that all electrical values fall within specifications. Be sure however, to disconnect the oil pressure switch from the PCM during resistance and continuity checks to prevent damage to the controller.
NOTE: The oil pressure switch (es) form part of its /their control circuits and its /their resistance must therefore be checked as well. Replace switches that do not conform to the manufacturer’s specifications only with OEM parts, clear all codes, and rescan the system to see if the code returns.
Be aware that replacing oil pressure switches can sometimes make it appear as if the problem had been resolved. Therefore, do NOT assume that the problem had been resolved simply because the oil pressure warning light does not illuminate immediately, or does not go out when the engine is started.
At this point, it is necessary to verify that the oil pressure does indeed fall within the range specified by the manufacturer, and this can only be done by attaching a pressure gauge to the engine. Bear in mind that even if the scanner shows the oil pressure to be OK, the scanner uses the same information the PCM does, which means that both the PCM and the scanner can conceivably indicate an oil pressure condition that is predicated, or based on incorrect input data.
Nonetheless, make a note of the oil pressure indicated by the scanner both when the engine is idling, and at the engine speed (usually, 3000 RPM) the manual says the oil pressure must be checked at for future reference. It might be worth noting at this point that if the oil pressure switch is removed from the engine, the scanner will NOT record or display an oil pressure reading.
NOTE: Mechanical oil pressure gauges can be had from almost any auto parts store for a few dollars. Most gauges also come with a variety of fittings to make it possible to connect the tubing to almost any engine at the point where the oil pressure switch screws into the engine. However, in the event that the correct fitting is not supplied with the gauge, do NOT force an incorrect fitting into the engine.
If another size fitting is required, use the male threads the oil pressure sender as a sample, and buy the CORRECT fitting from a hardware store to prevent damage to the engine, which damage could make it impossible to screw the oil pressure switch back into the engine.
NOTE: This step assumes that the oil in the engine is of the correct type and grade, up to the proper mark, in good condition, and that there are NO mechanical noises present when the engine idles. This step also assumes that the oil pressure switch is not leaking; although leaking oil pressure switches are common, they seldom leak so much that oil pressure is affected, but a leaking oil pressure switch MUST be replaced, nevertheless.
Make sure that the engine is switched off and cold or at least cool, and remove the oil pressure switch. Use the CORRECT fittings to attach the oil pressure gauge to the engine where the oil pressure switch came out, and make sure that all connections are properly tightened to prevent oil squirting all over the engine when the engine is started.
Make sure the tubing between the engine and the gauge is routed away from all hot and/or rotating components, and secure the gauge with some duct tape or similar material to prevent it falling. Start the engine, and allow it to idle.
The gauge may take a few seconds to register a reading, but it should stabilize after about ten seconds or so. Note the reading, and compare it to both the value displayed by the scanner earlier, and the value specified in the manual. The readings should match the pressure value stated in the manual very closely: if they do not, but all electrical values (as tested earlier) fall within specifications, allow the engine to warm up while monitoring the pressure gauge.
There may be very slight drop in the pressure indicated by the gauge as the engine warms up. Provided the oil pressure does not fall below the minimum specified value when the engine is at operating temperature, i.e., the radiator fan has come on, and turned off again, the slight drop in pressure is normal, and not necessarily a cause for concern.
WARNING: If the oil pressure drops below the minimum specified value, do NOT continue this procedure, since engine failure could be imminent. Switch off the engine immediately, and refer the vehicle to a competent repair shop for professional diagnosis and repair.
If the oil pressure as indicated on the gauge remains stable, and within acceptable limits when the engine is hot and idling, raise the engine speed to 3000 RPM, or the speed recommended by the manual, and maintain this speed for at least 30 seconds.
Compare the obtained reading with both the reading shown on the scanner earlier, and with the value specified in the manual. Both readings should closely match the value stated in the manual.
NOTE: If the oil pressure drops continually while the engine is running at 3000 RPM, or drops while the engine is warming up, there is a mechanical issue inside the engine that allows oil pressure to escape through overly large clearances. If this is seen to happen on the oil pressure gauge, refer the vehicle to a competent repair shop for professional diagnosis and repair.
Most problems of this nature are beyond the skills, knowledge, and equipment available to most non-professional mechanics to diagnose and repair.
If repairs to wiring, or replacing the oil pressure switch produce oil pressure readings on a scanner that fall within acceptable limits as stated in the manual, and these readings are confirmed by physically checking the oil pressure with a mechanical gauge, the repair can be seen as successful.
However, oil pressure readings that just barely comply with acceptable lower limits are indicative of excessive wear, or other mechanical issues inside the engine. In these cases, merely replacing the oil pressure switch will NOT correct the issue; replacing, or rebuilding the engine will be a more effective long-term solution.
Codes Related to P0520
- P0521 – Relates to “Engine Oil Pressure Sensor/Switch Range/Performance”
- P0522 – Relates to “Engine Oil Pressure Sensor/Switch Low Voltage”
- P0523 – Relates to “Engine Oil Pressure Sensor/Switch High Voltage”