Fault code P252C – engine oil quality sensor circuit low

Fault code P252C is called “Engine Oil Quality Sensor Circuit Low” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.

Technical description and explained code P252C

The OBD-II fault code P252C is a generic fault code defined as “low signal in engine oil quality sensor circuit”. It is set when the Powertrain Control Module (PCM) detects a low signal in the engine oil quality sensor circuit or the engine oil sensor itself.

Fault code P252C – engine oil quality sensor circuit low

The engine oil quality sensor is designed to monitor the condition so that proper quality lubrication of internal engine components is assured. In most cases, the engine oil quality sensor is installed on or inside the engine oil pan.

All major car manufacturers recommend monitoring the quality and changing the engine oil at least once a year. Even if the distance traveled is significantly less than recommended.

When the PCM detects a low signal in the engine oil quality sensor circuit, code P252C is set and the Check Engine light may illuminate. In some cases the PCM may shut down the engine to prevent damage to internal components.

Symptoms of vehicle malfunctions

The main signal that an error P252C has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.

It can also be warning signs such as:

  1. The “Check engine” control lamp on the control panel will light up (the code will be stored as a fault).
  2. Low oil pressure indicator may illuminate.
  3. Oil change message on the instrument cluster.
  4. Bad engine start, or complete failure to start.

Error P252C related to oil quality and pressure is considered serious, it is recommended to eliminate it as soon as possible. As poor lubrication can cause irreversible internal engine damage.

Factors that can cause this error code

The error code P252C can mean that one or more of the following problems have occurred:

  • The engine oil quality sensor is defective.
  • Engine oil is of poor quality.
  • Exceeded oil change interval.
  • Low engine oil level.
  • Faulty or damaged wiring harness.
  • Corroded, damaged, or loose connector.
  • Blown fuse or fusible link.
  • Sometimes faulty PCM module is the cause.

How to fix or reset OBD-2 code P252C

Some suggested steps for troubleshooting and fix the error code P252C:

  1. Read all data and stored error codes, using an OBD-II scanner.
  2. Clear the codes and check if error code P252C appears again.
  3. Check the level and condition of the engine oil. If necessary, replace the oil along with the filter.
  4. Check the wiring connections and connectors and fuses.
  5. Inspect the oil quality sensor.
  6. Check the sensor with a digital multimeter, and replace it if necessary.
  7. Pay attention to mechanical wear and tear on the engine. Physically check the oil pressure with a mechanical pressure gauge.

Diagnose and repair of problems

Check that the oil level is at the proper level, that it is not diluted with fuel or coolant, and that it is not of a thick, tarry consistency. If necessary, refill or replace the oil before proceeding with further diagnosis.

Perform a thorough visual inspection of the wiring to look for damaged, burned, disconnected, shorted, or corroded wires and connectors. If necessary, repair, clear the P252C code and re-scan the system to see if the code returns.

Check the wiring with a multimeter

After no visible damage is found, check the oil quality sensor for resistance, ground and reference voltage. Compare all readings with those in the manual. If necessary, replace the wiring to ensure that all readings are in accordance with the manufacturer’s specifications.

Remember to disconnect the oil quality sensor from the PCM during resistance and continuity checks to prevent damage to the controller.

Oil pressure check

It is necessary to make sure that the oil pressure is within the range specified by the manufacturer, this can be done by attaching a pressure gauge to the engine. Using a scanner is not recommended because the scanner uses the same information as the PCM.

The PCM and the scan tool may indicate an oil pressure condition that is based on incorrect data.

It may take a few seconds for the gauge to record a reading, but after about ten seconds it should stabilize. Record the reading and compare it to the value in the manual.

Allow the engine to warm up, watching the gauge reading. As the engine warms up, there may be a slight drop in pressure indicated by the pressure gauge. But oil pressure should not drop below the minimum specified value when the engine is at operating temperature.

Oil pressure readings that fall below the acceptable lower limits indicate excessive wear or other mechanical problems inside the engine. In this case, simply replacing the oil quality sensor will not solve the P252C error.

On which vehicles does this problem occur most frequently

Fault code P252C can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:

  • BMW
  • Buick
  • Cadillac
  • Chevrolet
  • Ford
  • GMC
  • Mercedes-Benz
  • Volkswagen
  • Volvo

Fault code P252C can sometimes be found with other errors. The most common are the following: P252A, P252B, P252D, P252E.


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