P0171 Fault Code

[The_Limey]

So whilst waiting for parts to fix my current AC problem, The Money Pit decides to throw me a new and interesting problem. I pulled the P0171 code (system too lean - bank 1) for perhaps the fourth time today since buying the car in November. Normally the CEL shuts off after a few days and my wife reports no adverse symptoms (surging or lack of power) whilst driving the car.

Freeze frame information:
------------------
Fuel Status = 0 byte
Engine Load = 48.235 %
Engine Coolant Temperature = 95 °C
Fuel Trim Bank 1 Short Term = -2.344 %
Fuel Trim Bank 1 Long Term = 29.688 %
Intake Manifold Pressure = 11.458 psi
Engine RPM = 2,510.5 rpm
Speed (OBD) = 51 km/h
Timing Advance = 13 °
Intake Air Temperature = 28 °C
Mass Air Flow Rate = 18.09 g/s
Throttle Position(Manifold) = 33.725 %
Run time since engine start = 457 s
Fuel Level (From Engine ECU) = 77.255 %
Distance travelled since codes cleared = 759 km
Evap System Vapour Pressure = -333.25 Pa
Barometric pressure (from vehicle) = 14.214 psi
Catalyst Temperature (Bank 1,Sensor 1) = 567 °C
Voltage (Control Module) = 14.249 V
Engine Load(Absolute) = 45.49 %
Commanded Equivalence Ratio(lambda) = 1
Relative Throttle Position = 21.176 %
Ambient air temp = 17 °C
Absolute Throttle Position B = 34.118 %
Accelerator PedalPosition D = 33.725 %
Accelerator PedalPosition E = 16.078 %




End of report.

I've looked into several threads on the forum which suggest the culprit could be anything from a dodgy MAP or O2 sensor, to an aging fuel pump. The AC debacle has cost me a bunch, and I'm currently unemployed. Without the luxury of just replacing parts until the problem goes away, could anybody help me join the dots up and make sense of what might be causing this fault code?

Edit: Since reading an article about how 02 sensors work and how to test them, I setup Torque on my tablet to plot a graph of the voltage outputs from both 02 sensors. I assume sensor 1 is upstream of the cat and sensor 2 is downstream of the cat. I'm also going to assume the upstream sensor is the one used for fuel trim, and the downstream sensor is used more for monitoring the efficacy of the catalytic convertor itself. Sensor 1 seemed to be oscillating between its minimum voltage and about 0.7V as the article describes. It also talked about introducing a vacuum leak or propane charge to the system in order to provoke a spike in the readings. I'm not sure if this is needed, or whether the oscillations are sufficient to rule out a fault 02 sensor?

[EAD15]

I had a faulty O2 Sensor (upstream) that appeared to spec out just fine. Only under specific engine loading, throttle position, and below a certain coolant temp would my car have problems.

Sometimes it's easier to hang a part than try to diagnose the problem. Since that isn't really an option for you right now, I would begin by checking the air intake hoses for cracks. Unmetered air entering the system would definitely trigger a "lean" condition.

On the plus side, it would also be the cheapest for a (temporary) fix. A strip of duct tape over the crack(s) and you are back in business.

[The_Limey]

There's a section just after the air filter assembly that has been wrapped in tape. I'll have a closer look at this tomorrow when I pull everything apart to tackle the AC. I've also read on the Chevy Wave forum a dirty MAF sensor can trigger the same code.

[xintersecty]

There's a section just after the air filter assembly that has been wrapped in tape. I'll have a closer look at this tomorrow when I pull everything apart to tackle the AC. I've also read on the Chevy Wave forum a dirty MAF sensor can trigger the same code.

Good luck on the AC. Take pictures and let us know the results on your AC thread. I ended up replacing my CAT and I had a poor CAT code. There is a member here trying to sell a new air hose. It may fit your car: http://www.aveoforum.com/forum/f81/a...-sensor-19598/

[The_Limey]

I'm gonna go out on a limb here and say I think this might be part of the problem:

[xintersecty]

I would say that is a cracking good find!

[The_Limey]

I would say that is a cracking good find!

Mate, that's terrible. So the hose the guy is selling that you provided a link to, is that for a different model? If it's just the articulated rubber piece, mine doesn't have a sensor there.

[xintersecty]

I tried searching online at Rockauto for a 2009 Pontiac G3. I can't find any pictures. The hose that KDR is selling is more like my setup and I have the older 1.6 engine setup. I think the later models had a different engine setup.

Yah, sorry about my pun at least it does not suck as bad as that hose.

[The_Limey]

Yeah, I think you're right. I'm after part 17 from the diagram which includes the MAP sensor. The cheapest I've found it is $166. No wonder the last guy just taped it up. Think I need to search some wreckers...

[xintersecty]

Interesting. If I look at part 17 above, it's like the part KDR is selling when I look at your other pictures, the hose comes out of the air box and then goes down. Tonight I will snap a picture of my engine setup.