I have a 2005 XC90 2.5 Turbo.

Onboard computer states I get an average of 15mpg but when I refuel and divide miles driven by fuel added, it equates to 22mpg.

The check engine light came on a month ago. Did diagnostic scans from multiple auto repair shops with a code of P2177 (bank 1 lean). I have replaced the MAS (diagnostic reveals 0.83 mg/cm when it should be 1.0 thus the CPU is adding more fuel to compensate for lower value on MAS,therefore, onboard computer shows lower mpgs and triggering the check engine light). I also replaced the fuel pressure sensor, fuel filter, and upstream O2 sensor. Did not take care of problem and still pulls code. Took it to a Volvo dealer yesterday. Their diagnostic reveals the following:

ECM-212C (Long term fuel trim, bank 1 - Signal too high
ECM-21EC (Long term fule trim, bank 1 - Signal too high

Tech at dealer replaced the following to attempt correcting the problem:

Oil trap & attendant components, cleaned throttle & PCV nipple, downloaded ECM software upgrade and replaced various hoses.

They obviously don't know how to fix it. Does anyone know if it is a correlation between the onboard computer and acutual mpg, which pulls the check engine light???????

 

The onboard (driver) information system does not have the capability to generate an event code/check engine light - it's a shared system which reads (pulls) onboard diagnostic information. Also, the DI system on my '05 has been off by 2.2 MPG since new - so trust your math at the gas station, not the computer, but I know that's not the question at hand that you're trying to solve for...

If your check engine light still hasn't gone after after 6-10 on/off ignition cycles since your previous repairs, or if it goes out and then reappears after the code has been cleared, it's almost always a problem with the heated O2 sensor. I can't tell you how many times I've heard of folks receiving a faulty new sensor right out of the box. If it's not the sensor, the second most common problem is intermittent fuel pressure issues (pump) which is tough to diagnose. A substantial exhaust and/or intake leak could possible trip LTFT, but rare. Good luck!

 

Hello,

I'm also having the exact same issue with the CODES:
(ECM-21EC & ECM-212C Long-term fuel trim, bank 1 : Signal too high)
on 2005 S60 2.5T - B5254T2

I had the breather hose cracked and replaced, I removed the intake system too and dis-assembled and cleaned the entire oil trap system + used new clamps too. It was a bit caked in the pipes going into the engine, but not clogged or that bad at all... Before this procedure i was noticing a lot of oil in the turbo when I took the charge pipe coming off the turbo and going into the front mount intercooler... I checked all the hoses coming off the turbo and none were worn/cracked. I'm getting 17L/100KM ((13.8MPG))
(But I Should be at -/+ 10L/100KM [[23.5 MPG]])

The hose that goes Beside the "Banjo Bolt" under the intake was also cracked/broken. I replaced both the Maf and Upstream O2 with the exact same part numbers as OEM , fuel pressure sensor(on fuel rail) ,fuel filter, spark plugs(Iridium), and new muffler (it corroded and caved internally causing clogging. I also removed the throttle body and cleaned it, the car started to die after a few seconds on cold starts. when the car is at idle, there needs to be about 1% space around the throttle place for air to get by. since mine was a bit caked, the car would die out.

I had a professional mechanic replace the timing belt+water pump as well.

Cleared the codes using VIDA tonight, and the light comes back on in 50 KM or so. Currently at 160,000 KM with new air filter added to the list, but check engine light keep throwing this code. I cleaned the 2 connection that connect the 02 sensor and maf sensor with electrical contact cleaner as well just for the heck of it too. I running out of things to check here...

I would appreciate any input from anybody.

Thank you everyone

I have access to the VIDA software as well....

 

My advice is to return to the dealership. I'm sure you paid an mount just to get the car running right. But since you've been throwing parts into this vehicle without testing, things can get a bit complicated. What made you decided to replace the fuel pressure sensor? I had someone install the wrong pressure sensor once for a non-turbo. I found an exhaust leak in the manifold. I found the cat being at fault, and an easy check was to pull the 02 and inspect it with a camera,pump. I can go on and on, but you need the freeze points from vida when the fault occur, hook a fuel gauge and compare with vida. Duty cycle is important as well.

 

Complicated AND expensive!