ODBII diagnose - P0131 & P0171

[masraum]

2003 Jeep Liberty 3.7L V-6.

P0131 - Oxygen O2 Sensor Circuit Low Voltage (Bank 1, Sensor 1)

P0171 - System Too Lean (Bank 1)

Considering 2 codes that point toward issues with the same O2 sensor, I'm thinking bad O2 Sensor. Does that seem reasonable?

[Tobra]

Almost too reasonable. I think they have loaner sensor sockets at the FLAPS.

Kroil or PB blaster would not be a bad idea.

[masraum]

Originally Posted by Tobra

Almost too reasonable.

That's what I'm afraid of, but it seems like a >95% likelihood.

It's not my car, it's my sons. He's not mechanical, and I've begun thinning things out because we are selling the house and downsizing into an apt in town. So he'll be taking it somewhere. I don't want to screw with getting under the thing. He's really, REALLY not mechanically inclined, so I'm not going to recommend that he try it.

[john70t]

Originally Posted by masraum

It's not my car, it's my sons. He's really, REALLY not mechanically inclined, so I'm not going to recommend that he try it.

Unplug one thing. Unscrew one thing. Take new part out of package. Reverse step to assemble.

Have him call me. I'll tell him that he is lucky to have a dad with mechanical knowledge, and that he should try and learn as much as possible while he can, because he's going to be paying other people big money to do the same task for the rest of his life.

[John Rogers]

On all three of our cars we have now there are two O2 sensors, sensor 1 is before the cat and sensor 2 is after the cat. In doing some searching, the codes you listed are the same as for our Chevy, Caddy and Taurus which is the nice thing about ODBII standardization. In this case, it points to a condition that is too lean for the brain to adjust for. Since you have a V6, you would need to see which is bank 1 and which is bank 2 but in most cases the replacement of all the injectors is in order just to be safe. It could be an air leak but would have to be in a rubber hose that feeds only one side of the engine such as the PCV line. In our Caddy witha V8, the PCV feeds bank 2 or the rear side of the engine.

[Rick Lee]

I had a CEL in the 993 and the code was for a lean right bank. Turned out to be clogged injector. I pulled the fuel rails, had the injectors ultrasonically cleaned and that fixed it. Been fine for eight years since.

[wdfifteen]

P0131 is the heater circuit. It is fused and it's easy to check with a meter. One of the four wires to the o2 sensor should have 12 volts to it with the key on. If it does the problems the sensor. If not, it's more likely the fuse. I'm not sure if a non-working heater can cause another code on your car or not. Mine Tundra doesn't.

[IROC]

A P0171 can be different things that end up manifesting themselves as a bad O2 sensor. In other words, sometimes people think the O2 sensor is bad when really the O2 sensor is just the messenger. I chased a P0171 code on my old Tacoma for awhile (replaced the O2 sensor and continued to throw P0171 codes). It ended up being the MAF sensor. It just needed cleaning. $5 fix.

I've found it useful to just type in "jeep liberty p0171" or something similar into google and read what will probably be a huge amount of stories of what this code might actually mean on your engine (that's how I found the MAF sensor fix on my Tacoma).

Good luck. OBD2 is a blessing and curse.

[911SauCy]

^^^ This, make your search more vehicle specific, also start with the simple things with a P0171 code.

I had a Regal GS (supercharged 3.8) that threw this code for a year. I started with and performed all the easy/low buck stuff until I was able to pinpoint that the Lower Intake Manifold had a pin-hole in it.

The old gasket wasn't fond of the 13psi increase in boost... Muaahahahaaa

Good Luck

[rick-l]

Stop with the noise.

P0131 means the O2 oxygen sensor's voltage remained low for longer than 2 minutes. (not to be confused with P0031 which is the heater).

P0171 means that an oxygen sensor in bank 1 has detected a lean condition (too much oxygen in the exhaust) which in signal terms means the voltage from the sensor is too low. The ECU tries to richen it up and has exceeded the threshold that the manufacturer thinks is reasonable.

Let him see if this fixes it. Harbor freight has an OXS tool for $6 is it is necessary to have an offset.

[IROC]

Originally Posted by rick-l

P0171 means that an oxygen sensor in bank 1 has detected a lean condition (too much oxygen in the exhaust) which in signal terms means the voltage from the sensor is too low. The ECU tries to richen it up and has exceeded the threshold that the manufacturer thinks is reasonable.

All I'm saying is that a P0171 doesn't necessarily mean the O2 sensor is bad. I found it better in the end to get smart on this stuff rather than replace part$ until the problem went away.

YMMV.

[rick-l]

Originally Posted by IROC

All I'm saying is that a P0171 doesn't necessarily mean the O2 sensor is bad. I found it better in the end to get smart on this stuff rather than replace part$ until the problem went away.

YMMV.

That is true but P0131 is definitely a problem with the OXS (or associated circuitry - check the wire hasn't shorted to the exhaust etc) that could lead to P0171 being set

[masraum]

Thanks all, lots of good info. The Internet had mentioned problems with MAF, vacuum leaks, etc.... Maybe we'll try a couple of the easy things first. I'm just not going to be doing much work on this thing myself and he's not mechanically inclined. I've already sold a bunch of my tools, floor jack, jack stands, creeper. I'm trying to get the house sold, get moved out, etc... Earlier this year, I probably would have just done it myself, but not now with everything that's going on. I wouldn't have him do it because I can picture him breaking the O2 sensor off in the exhaust, and I don't want that headache.

[masraum]

He dropped it off at the shop this morning. It's ready to pick up. $160, O2 sensor. I'm assuming it was $60-80 for the sensor and the rest for labor. All things considered, not too bad.