For the past several months my 2007 Volvo S40 AWD has been experienceing "episodes" with a dash display of Reduced Engine Performance. These episodes reduce the accelerator response but allow me to continue to maintain highway speeds. I would not want to make any quick passing manuevers while this is happening as acceleration is sluggish. If I pull off the road and restart the car the problem is cleared. This does not trigger a check engine light. We went the route of changing the Turbo Boost Control with no change in the problem. Within the past moth we've finally discovered a pattern that is repeatable and consistent. With a full tank of gas the episodes disappear. As soon as we get below about 2/3 of a tank the episode happens on every commute (both ways). I would be interested to hear opinions on an approach to this problem.

 

Since you mention fuel then start with a fuel pressure check when it's acting right and then again when it's acting wrong. I've never experienced this problem so this is a WAG for sure. I'm thinking you would look for some difference between the two readings. If it's just a momentary trigger to the ECM that starts the reduced performance then you might not see any difference.

 

Hello,
I'm experiencing the exact same issue with my 07 S40 T5. I have not had the same experience with full/not full fuel tanks however. Were you able to fix your issue and if so can you please share what worked for you. Thank you for any assistance as this has already become a very expensive issue at this point...

 

any other symptoms like longer than usual cranking when starting up first thing in the morning? the fuel system seems a reasonable area to be the first place to check out - pump, relay, pressure regulator etc. You can try swapping out the fuel pump relay - if that cures it then it may point to a fuel pump on its way out (there should be a way to measure its current draw - maybe its overheating...)

 

Well I finally experienced the message. It was the Fuel Pressure Sensor. 10 minute fix but not exactly cheap.

 

I have the same experience with my Volvo S60 T4 2011 model but has never focused on the fuel volume as such. If you got it right please share with me

 

Hi my 2010 Volvo S40 giving me the reduced engine performance message , when I press the mileage counter button its giving me codes 232 , 073 and 072 , anybody shed any light please , just bought this car and wasnt expecting this

 

Is it throwing any OBD codes?

 

Those are not OBD codes and that's not how you check OBD codes. There is no built in OBD scanner. You have to plug into the OBD port under the dash with a scan tool to retrieve codes -

 

hey I know this was a long time ago but did u get it fixed, my car is having the same issue?

 

It sounds like you've been dealing with a frustrating issue with your Volvo S40 AWD. Based on the symptoms you've described, it seems like the problem may be related to fuel delivery or fuel system components.

Here are a few steps you could consider taking to address the issue:
Fuel System Inspection: Since the problem seems to occur when the fuel level drops below a certain point, it's possible that there's an issue with the fuel pump or fuel filter. A mechanic could perform a thorough inspection of the fuel system to check for any clogs, leaks, or other issues that may be affecting fuel delivery.
Check for Faulty Sensors: The Reduced Engine Performance warning could be triggered by faulty sensors related to fuel delivery or engine performance. This could include sensors such as the mass airflow sensor, oxygen sensor, or throttle position sensor. A diagnostic scan of the vehicle's onboard computer system may reveal any stored fault codes that could point to specific sensor issues.
Inspect Electrical Connections It's also possible that there could be an issue with electrical connections related to the fuel system or engine management system. Loose or corroded electrical connections can cause intermittent problems like the one you're experiencing. A mechanic can check all relevant electrical connections and wiring harnesses for signs of damage or corrosion.
Consider Fuel Additives: Since you've noticed that the problem seems to occur when the fuel level drops below a certain point, it's possible that there could be contaminants or deposits in the fuel system that are affecting performance. Using a fuel system cleaner or additive designed to clean fuel injectors and remove deposits from the fuel system could potentially help resolve the issue.
Consult with a Specialist: If the problem persists despite your best efforts, it may be worth consulting with a specialist or taking the vehicle to a Volvo dealership for further diagnosis. They may have specific knowledge and experience with common issues affecting Volvo vehicles, and they may be able to provide more targeted advice or solutions.

Overall, addressing the issue may require a combination of diagnostic testing, component inspection, and potentially some trial and error to identify and resolve the underlying cause. Working with a qualified mechanic or Volvo specialist can help ensure that the problem is diagnosed accurately and resolved effectively.