ok will check this weekendWith that kind of mileage my first guess would not be an O2 sensor. It very well could be but that's not the first guess. Have you done spark plugs on this van? They were due at 105K along with your timing belt service.
The first thing I'd do with this vehicle is plug in a scan tool and take a look at fuel trims to see the extent of the lean condition and see if it's happening on the other bank but just not to the extent of setting a code or if the problem is really localized to bank 1.
There's just a lot more to it than throwing an O2 sensor at it. Besides, if you're going to throw an O2 at it you might as well throw both upstream and downstream O2 on that bank at it since both contribute to fuel strategy on these vans. I would also check the intake tube that goes from the air filter box to the intake manifold. I've seen jiffy lube places leave those loose and cause lean conditions.
O2 sensors are the 2nd sensors on the cats, this code is coming from the air fuel ratio sensor.Ah The O2 Sensors,....Lovely....Thnaks Guys I'll Start With That
^+1. Replace with OEM parts, not the random stuff you see at the stores and online. Denso is the OEM part for the exhaust sensors. Like John said, thoroughly diagnose the problem first.Woah! Slow down there folks. A DTC does NOT tell you what part to change. Rreplacing an O2 sensor is just a guess and may be a total waste of money. P0171 means the computer is correcting for a lean condition on bank 1 (the rear bank.) A lean condition can be caused by any number of things. It could be a vacuum leak, it could be a Mass airflow sensor, it could be low fuel pressure, it could be lots of things.
We need a lot more info. What kind of miles on the van? Are there any other codes besides P0171? It will take a scan tool and looking at some live data to determine the issue and why it's running lean. If you don't have that capability then I'd recommend getting a diagnostic done on it BEFORE replacing ANYTHING. Often times parts are replaced, that don't need replacing, and end up getting replaced with low quality and even non-working aftermarket parts, causing the issue to get worse before getting better.
This code could come from the downstream sensor or the upstream sensor since both contribute to fuel trims. The code could also come from a vacuum leak such as a torn or loose intake boot. The code sets when the computer has to add more than a specified percentage of fuel to keep the engine in stoichiometric.O2 sensors are the 2nd sensors on the cats, this code is coming from the air fuel ratio sensor.
Thoroughly diagnose the problem before you replace the sensor. Lean condition can be a lot of things. I would check the intake system first, check the intake tube. (airbox to throttle body)