An oil pressure sending unit controls either the oil pressure light or gauge in your dashboard. When it detects oil pressure in the vehicle, a switch trips and either the light shuts off, or the gauge becomes active. A faulty oil pressure sending unit can result in inaccurate oil pressure readings and warnings. So, it is important to recognize the signs of a sending unit that needs to be replaced. Here is a short list of symptoms that may mean you should get the oil pressure sending unit tested or replaced.
1. Check Engine Oil Light Remains On
First of all, you should always check your engine oil when the warning light comes on, even if you’re sure it should be full. Oil could be leaking from your engine, which is a more immediate, potentially costly repair.
If you have checked the level of your car's engine oil and it is full, but your car's engine oil light is still on, your sending unit may be indicating a false positive, in which case it will need to be replaced.
2. Oil Pressure Reported as Extremely High or Low
If your car's dash is equipped with an oil pressure gauge, look for signs of extreme high or low oil pressure levels. It is not uncommon for some older vehicles to have low oil pressure when the car is first started. However, if the oil pressure gauge continues to show a low pressure reading even after the car engine is warm, and there are no other problems that you can tell, the culprit may be a defective oil pressure sending unit. The same would be applicable if the gauge reports very high oil pressure levels as soon as the car's engine is started.
3. Oil Pressure Reporting Erratically
This is perhaps the most telltale sign of a malfunctioning sending unit. If your oil pressure gauge or engine oil warning light have very sporadic behavior—the gauge moving from low to high or high to low randomly or the light coming on and off frequently—you can be sure there’s a problem with the sending unit.
Having faulty readings for your engine oil can be hazardous, since you’ll never know if/when your engine oil is truly low, so it is recommended that you repair it quickly. An oil pressure sending unit is not hard to replace, and for most car makes and models, it is inexpensive as well. In fact, replacing a sending a unit is something most DIYers can try for themselves.