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Oil Pressure Sending Unit: Understanding the Overview, Symptoms, Diagnosis, and Replacement Costs

By R&D
Published on December 29th, 2023

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The oil pressure sending unit (also referred to as an oil pressure switch or oil pressure sensor) is a critical component in the vehicles engine system. The device is critical in ensuring the vehicle’s engine operates within safe oil pressure ranges. This article provides an overview of the purpose, function and operation of the oil pressure sending unit, symptoms of a faulty unit, diagnostic strategies, and replacement costs.

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Overview of the Oil Pressure Sending Unit:

Maintaining proper oil pressure is vital for ensuring smooth engine operation and preventing damage to engine components. The primary function of the oil pressure sending unit is to monitor the oil pressure within the engine and provide real-time feedback to the vehicle's control systems as well as to the vehicle operator. The sending unit generates a signal representative of the current engine oil pressure and supplies this signal to the Engine Control Module (ECM) as well as to the oil pressure gauge on the vehicle’s dashboard. In cases where engine oil pressure falls below a minimum acceptable value, it actuates the oil pressure warning light on the dashboard.

Any malfunction in the oil pressure sending unit may cause incorrect or absent signals to be supplied to the ECM and dashboard indicators, resulting in a misleading indication of engine oil pressure.

Symptoms of a Faulty Oil Pressure Sending Unit:

A malfunctioning oil pressure sending unit can lead to a range of symptoms that reflect an inaccurate reading of oil pressure. This can cause unnecessary concern to the vehicle operator that there is insufficient oil pressure to properly lubricate the engine. Symptoms of a faulty oil pressure sending unit may include:

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1. Fluctuating or Erratic Oil Pressure Gauge: A primary function of most oil pressure sending units is to provide a real-time signal representative of the engine's oil pressure to the vehicle’s oil pressure gauge. When the sending unit malfunctions, it can send inconsistent or incorrect signals to the gauge. This may cause the gauge needle to fluctuate rapidly between high and low pressure, even though the actual oil pressure remains constant.

2. Constant Low Oil Pressure Reading: A faulty oil pressure sending unit can cause the oil pressure gauge to incorrectly display a constant low-pressure reading when actual engine oil pressure is within acceptable limits.

3. Illuminated Malfunction Indicator Lamp (MIL): When the oil pressure sending unit fails, the vehicle's onboard diagnostics system can illuminate the Malfunction Indicator Lamp (MIL). The MIL provides a visible indication that a fault may be present in the engine or in a monitored component. While the oil pressure sending unit may not directly cause engine damage, it is important to have the vehicle inspected by a professional technician to determine the underlying cause and prevent potential problems.

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Diagnostic Tips:

To check for a faulty oil pressure sending unit, it is necessary to visually inspect the unit for damage, and perform tests to locate any signs of malfunction. Use the following procedures to identify a faulty oil pressure sending unit:

1. Visual Inspection: Visually inspect the wiring and connections at the oil pressure sending unit for signs of damage, corrosion, or loose connections.

2. Using a Mechanical Gauge: If you suspect a faulty sending unit, temporarily connect a mechanical oil pressure gauge to the engine to obtain an accurate reading. This can help determine whether the issue lies with a faulty sending unit or if the actual oil pressure is not within acceptable limits.

3. Using a Code Reader or Scan Tool: Modern vehicles store Diagnostic Trouble Codes (DTCs) related to sensor malfunctions. You can use a Code Reader or Scan Tool to retrieve and identify stored DTCs related to the oil pressure sending unit.

Repairs and Cost Estimates:

The cost of replacing an oil pressure sending unit can range from $50 to $150 or more, including parts and labor. However, the cost may vary depending on vehicle make and model, the location of the unit, and labor charges. Always check with local auto parts stores, online retailers, or your vehicle's dealership for the most up-to-date pricing.


The oil pressure sending unit may be a small component, but its role in ensuring engine health and performance cannot be underestimated. Recognizing symptoms of a faulty unit and promptly addressing the issue through proper diagnostics and repair can prevent potential engine damage and ensure accurate oil pressure readings. Regular maintenance, including checking wiring and connections, contributes to the proper functioning of this essential component. By understanding the significance of the oil pressure sending unit, vehicle owners can take proactive steps to maintain engine vitality and enjoy a reliable and smooth driving experience.

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