This is a documentation of my solutions to two problems I encountered with my 2012 Volvo S80 3.2L.

My first problem was when trying to start my car the engine turned and sputtered. The engine revved up to 1.6k RPMs which is normal for a cold start then immediately died. My initial diagnosis was hard because I couldn't replicate the issue later when I tried to. I found that my hose clamp between the air filter housing and the intake manifold was loose and my assumption was that air was slipping in through because there was not a seal. The air bypassed the mass airflow center and therefore the ECM had an incorrect reading of the air entering the engine causing it to mess up the fuel to air ratio leading the car to run super lean and die. My fix was to tighten the hose clamp using a screwdriver and this issue immediately disappeared.

My second problem occurred when I was driving home I noticed a check engine light. I drove home and read the code from the ECM with my OBD2 reader. The code read the following, "Fuel Rail Pressure Sensor A Circuit High". I did some googling and found that the fuel pressure sensor is a common point of failure and can be replaced quite easily. Before I ordered the part I drove the car some more after clearing the code to make sure my diagnosis was correct. Immediately after starting the car, the pressure was 60 psi which is within the recommended range of 40-60 psi. Also, note that because the pressure sensor is constantly updating the pressure is constantly fluctuating by one to one-tenth psi. When I turned the car off the pressure dropped to half as expected. This I what I used to make my determination. I drove the car for a time and checked the FRP (Fuel rail pressure). It was stuck at 120psi and not fluctuating. The CEL (Check engine light) was not on at this point. From this, I assumed that the part was faulty after 10 years and that was being demonstrated in its solid value of 120. I purchased this from amazon as Volvo just rebrands the bosch sensor. When replacing it use this , for my s80 because when I turn it off the pressure drops I didn't need and couldn't figure out how to bleed the pressure off. I did it quickly as fuel was draining out. I recommend using a bit of oil from the dipstick to lubricate the o ring on the sensor before replacing it.

If anyone has any questions reply and I will reply as fast as I can.