My 2010 TL AWD showed an Emissions System warning a week ok (followed by an SH-AWD warning, which I believe is just a consequence of the first warning).

Was taking it to the dealer anyway, for a 100K service, timing belt, water pump etc. They cleaned up the fuel intake parts, but within 50 miles the warnings came back.

Returned to dealer, and they are now advising I need a new fuel pump. They say the existing pump is running at less than full capacity, so the engine is running lean.

However, the fuel economy has dropped from around 22 to around 16. There is also no evidence of any hesitation when accelerating (even hard), and cruising is smooth. Only symptoms I have noticed is it is taking maybe a second longer to start, and very occasionally there is slight hesitation when re-accelerating from slow speed (say after slowing for a corner). But only happens very occasionally.

Is it the fuel pump that is the problem?

 

the fuel pump is designed to last the lifetime of the vehicle.

this is what I would do your situation.
check to make sure the battery isnt 3 years or older.
next, clear the codes by taking off the negative terminal on the battery.
if the code comes back, which I think it will, you know you have a real problem.
take the vehicle to autozone to read the code.
I'm betting on an 02 sensor

 

I have read the codes: PO171 and PO174.
Both banks O2 sensors are lean.
So it still could be the fuel pump, I suppose.
Other things: MAF sensor, intake air leaks, dirty throttle, bad fuel, ... ?

 

Since the dealer did all that work with timing belt and cleaned up intake, adjusted valves, etc (obviously they removed the intake) you may have a vaccum leak so it goes lean. Ask the dealer to show you the short and long fuel trims on both banks If the short fuel trim follows the long fuel trim on its way up then its the fuel pumps (yes the SHAWD has two of them, one on each side of the gas tank that is curved in the middle for the shaft to go through), but if the long fuel trim stays stable while the short goes up then you have a vaccum leak, probably from the aluminum gasket under the intake manifold that they didn't change when they removed it (these don't last too long!) or the bolts aren't torqued properly.

PS, I think I got the short vs. long trims right, correct me if I am wrong.

PS. ask the dealer which pump has gone bad... the main left or the sub right and see the expression on their face. If they hesitate or tell you there is only one, well tell them to go f...

 

i would agree. if throwing both of those codes..not the 02 sensors...

Assuming those were the only 2 codes, service manual procedure says to check fuel pressure.

If pressure is OK, check valve clearance and adjust if necessary. If valve clearance is good, replace injectors (OUCH!!)

If pressure is LOW (not covering high pressure since this is a lean condition), check fuel pump and fuel feed pipe