Hey guys. Got the running lean code from the ODB2 reader. Just wondering where is a good place to start. I read earlier than its recommended for a compression check but i dont want to have to dig for my comp gage yet. Im assuming the O2 sensor is working since that code didnt come up. Well thanks for any help.

 

I have the same code. and was wondering the same thing. Could this be some sort of plugged injector?

 

The "lean condition" code is set when the long-term fuel trim value reaches a certain setpoint, +14% if I remember right. Whatever is going on, the PCM thinks the car is running lean. It could be a faulty O2 sensor (or the wiring), a fault in one of the other sensors that are used for the fuel trim calculations (IAT, MAP, TPS, coolant temp, battery temp, rpm, or any of the wiring associated with those), or an actual lean condition caused by a problem with one of the fuel delivery devices (fuel pump, fuel filter, fuel pressure regulator, fuel injector, or any of the wiring or tubing associated).

If the car isn't really running lean, then the PCM is dumping fuel in there to compensate, so performance/idle quality will likely suffer. It's not going to hurt your engine as much or as fast as a true lean condition will though. So it's best to start by assuming the worst... A seriously over-rich condition will shorten the life of your cat.

I'm guessing you have a '98 by your sig. That means you don't have a fuel filter worth checking (yet). Instead, check to make sure the fuel pressure at the fuel rail is 49 psi. If you have an auto, you can have a friend help and torque brake to provide engine load and see if it changes (more fuel required). A problem here could mean an issue with the pump, regulator, tubing, fuel pump wiring or (pathetically rare, if ever, on the plastic tank cars) the filter. A single injector won't typically cause a lean condition, even if it isn't firing at all (in which case you'd get a misfire code...). Rather than replacing the injectors at $60+ a pop, replace the plugs with fresh $1 coppers, drive for a little bit (hundred miles should do it, don't beat on it), and pull them to check for a lean condition (and/or overly rich condition) in one or more cylinders.

If one of the input sensors is faulty, it will usually throw a code for that sensor. Not always though. As long as the sensor is reading within an allowed band, the PCM thinks everything is fine, but the signal could still be incorrect. A FSM (maybe even a haynes manual) should list all the normal/expected voltages for the various sensors.

The Neon does have a bad rep for the O2 sensors. The factory units are by NGK, which are better than the aftermarket Bosch, but still drift more than most, even without throwing a code (the sensor thinks it's fine and the PCM agrees). Usually they tend to indicate a leaner-than-actual condition. Most people end up replacing them long before the lean code is set because of really, really bad performance and a really, really bad idle. not the best place to start if you're on a budget though, they typically run $75-100+ each (and yes, the downstream sensor does input into fuel trim for the '96-up Neons), depending on where you go.

Best of luck!

 

OK searched around and havent found this one. Im getting the PO172 running rich code could that just be from junk in the TB. or what ? I have new cat and O2 sensors and it is idling ruff on first start up. smooths out after it gets to temp.

 

OK guess I shoulda started my own thread, figured out after reading alot more about this to just do the diagnostics as described by RADARLOVE. hey if it works for the lean is must for the rich code also.
Thanks

 

I have a Dodge 2008 Caliber i bought from the first owner Feb 2015, and now a year later im having the same issues as i did in the begginning. The P0171 code. Lean Code. So they have done everything they can think of, its been in the shop for over 10 weeks total. they still have no clue. They replaced the valve cover gasket, spark plugs, fuel injectors,o2 sensors, computer,seals in all evap system, i think thats it, but it still has the service engine and the same code still. So any ideas?? I would hate to have to sue the people.