Hello everyone, I just made an account because I had a few questions about the issues I am having with my s40. Basically, I have a 2004.5 s40 2.4i with roughly 154,000 miles. The problems I am having are mostly electrical from what I can tell. The car will sometimes start hard and lack power at random times, I scanned the code and it said something about a fuel pressure sensor circuit low. Also when I turn the wheel at low speeds, the headlights will dim, the radio will cut off, and the gauges will reset (this happens spontaneously and power steering service required and ABS lights will come on for a split second). Lastly, this will happen very rarely, but the alarm triggered light will show up, and no damage is present) and I will get the key error try again message. I have no idea where to start, I've already replaced the battery, but this didn't really help the situation. Other than that, the car runs completely smooth. If anyone could help, that would be much appreciated!

 

On the newer models the fuel pressure regulator has been replaced by a fuel pressure sensor. This controls fuel pressure by varying the voltage sent to the fuel pump. This means 2 things. First is that our cars are VERY sensitive to changes in voltage. A good working battery and alternator is a must. Second is if the sensor goes bad it will cause the car to lose power as either too much or too little fuel is supplied. If this were my car I'd first verify the voltage of the alternator. If all is well with nice clean and tight cables, then I'd replace the fuel pressure sensor. If it still acts up I would suspect the fuel pump itself but not actually replace it unless it fails outright.

 

I appreciate the feedback, and could a failing fuel pressure sensor really cause the wide array of problems I'm having as far as the car not wanting to start at times, the key error message, and the radio cutting off only when I turn the steering wheel. I'm pretty sure the alternator is fine, but I'll have it checked. Btw, the codes I've scanned are related to fuel pressure (fuel pressure sensor circuit low voltage)

 

BATTERY Volvo's baby their batteries but they do go eventually. As Hudini said, good voltage is the heart of a Volvo.

 

Yikes, lots of strange behaviors. What you describe sounds like low voltage. This would cause the low fuel pressure, and *could* cause the other issues.

As the steering is electric assist then this too could be a symptom of low voltage as it doesn't draw any power until you move the steering wheel a certain amount. Then the power assist kicks on and it pulls too much power and your radio cuts out.

I'd suggest taking the car to have the charging system checked out at one of the local parts places like Advance or AutoZone or O'Reilly's, etc. They have a machine they wheel out to your car which tests how well the alternator is charging.

Then check the cables to make sure everything is clean and tight. Maybe remove the cables and use sandpaper to clean up the battery terminals and the cable ends where they bolt onto the battery. I've seen several cars with problems directly related to corroded cables. Sometimes the corrosion extends up under the cable insulation. That is a fun one to figure out.

EDIT: While starting if you ever hear a rapid 'click, click, click' then you know it's low voltage. This is normally the battery but sometimes it's a loose ground cable or corroded power cable.

 

Hey Hudini, I just had my alternator checked and apparently it's going out. Could a failing alternator cause these weird problems especially to the ones related to the fuel pressure sensor?
It's also very expensive to repair and I don't want to replace it and still have more problems, if that's the case, I'll probably sell the car.

 

absolutely! alternators can fail several ways - including not being able to produce enough current for a given load. Check out some of the Youtube vids for how to self test the alternator but the DIY just requires a volt meter. 1) engine off, measure the battery terminals - should be 12.6 or so. 2) start car, again measure at battery terminals - should be 14 - 14.5 or so. 3) turn on anything electric - high beams, rear defroster, AC blower motor on high etc. Measure at battery terminals - should stay in the 13V+ range. If the volts drop with all that load then you can suspect a cabling issue or alternator (more rarely it could be the battery). Turn off car and feel around the cables - anything very hot means you may have a bad connection or cable/terminal.

 

I agree with mt6127, a failed alternator can cause the low fuel pressure you experienced because of the way Volvo designed the fuel pump to be regulated by voltage. But please don't throw a bunch of money at it just yet. Check out the battery cables thoroughly first. A bad cable, positive or negative side, can cause the same symptoms. Use a multimeter set to ohms to check the resistance of the cables. While you have them off the battery you can clean the ends and the battery terminals. Look for loose connections, especially the back side of the alternator. Check the alternator pulley belt. Is it slipping, do you hear it squeal ever?

If all else fails and it's definitely the alternator look for an alternator rebuilder in your town. My little town in Knoxville, TN has one. They rebuild for 1/4 the cost of replacement. If you have to buy a reman try online. RockAuto is a good place for cheap parts if you don't mind non-OEM brands. If you must have OEM then try Tasca, SwedishParts, and many others. This will be the costlier option but you get an original Volvo part.

Let us know how it goes please.

 

Had the same issue on mine, tighten the battery terminals and this should fix the issue