Just to start this off i'm getting the usual p0171 code. The code comes on every time the weather is below 60 degrees. Stage 2 with the GM stage 3 2.99 pulley. I also have an AEM intake and colder plugs. I don't think it's normal for me to be getting this code, stage 2 runs pig rich and a tiny bit smaller pulley and intake shouldn't be doing this. Doing high end pulls also seem a bit lacking. If i take it do the dealer, they will blame it entirely on my intake since there is a GM bulletin about p0171 and aftermarket intakes. I'm confident that if/when i put the stock airbox on the code will still come up, but I would have to go back home (I'm at college) to get the airbox and it's a hassle.

This code never came on the first couple months i had everything on even in very cold weather, then all of a sudden i can't get away from it.

So should i take it to the dealer as it is now or wait until i get my stock box on?

 

Check all your intake connection for possible leaks.Also vaccume hoses and that your dipstick is seated properly.
Your AFR could be on the edge and causing the code when the temp drops,but I dont know enough about that stuff to say for sure.

 

I wouldn't take it in with the AEM on it , they will blame that no matter what . I would check the filter and clean the MAF and see how it goes .

 

Its probably the larger diameter intake causing it if you don't have any leaks. Either a retune or a smaller diameter intake will fix it.

P0171 is a fuel trim code. The lean in the code doesn't mean you are actually running lean. It means your fuel trim correction is in excess of 20% of where it should be.

 

Document ID# 1651743
2006 Chevrolet Cobalt


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DTC P0171
Circuit Description
The powertrain control module (PCM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. Fuel delivery is controlled differently during Open Loop and Closed Loop. During Open Loop, the PCM determines fuel delivery based on sensor signals, without heated oxygen sensor (HO2S) input. During Closed Loop, the PCM adds HO2S inputs and level of purge to calculate the short and long term fuel trim adjustments. If the HO2S indicates a lean condition, the fuel trim values will be above 0 percent. If the HO2S indicates a rich condition, the fuel trim values will be below 0 percent. The short term fuel trim values change rapidly in response to the HO2S voltage signals. The long term fuel trim makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1. A block of cells contain information arranged in combinations of engine RPM and engine load for a full range of vehicle operating conditions. The long term fuel trim diagnostic is based on an average of cells currently being used. The PCM selects the cells based on the engine speed and load. If the PCM detects an excessively lean condition, DTC P0171 sets.

DTC Descriptor
This diagnostic procedure supports the following DTC:

DTC P0171 Fuel Trim System Lean

Conditions for Running the DTC
• DTCs P0030, P0036, P0068, P0069, P0101, P0102, P0103, P0106, P0107, P0108, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0130, P0131, P0132, P0133, P0134, P0135, P0136, P0137, P0138, P0140, P0141, P0201-P0204, P0220, P0222, P0223, P0300, P0301-P0304, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0496, P0506, P0507, P1133, P1134, P1516, P1680, P1681, P2101, P2119, P2120, P2122, P2123, P2125, P2127, P2128, P2135, P2138, P2176 are not set.

• The engine is in Closed Loop status.

• The engine coolant temperature (ECT) is between -7 and +120°C (+19.4 and +248°F).

• The intake air temperature (IAT) is between -7 and +145°C (+19.4 and +293°F).

• The manifold absolute pressure (MAP) is between 15-100 kPa (2.2-14.5 psi).

• The vehicle speed is less than 132 km/h (82 mph).

• The engine speed is between 400 and 6,100 RPM.

• The mass air flow (MAF) is between 1-512 g/s.

• The barometric pressure (BARO) is greater than 72 kPa (10.4 psi).

• The fuel level is greater than 10 percent.

• DTC P0171 runs continuously once the above conditions have been met.

Conditions for Setting the DTC
• The long term FT weighted average value is more than a calibrated value.

• The above condition is present for more than 2 minutes.

Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.
Conditions for Clearing the MIL/DTC
• The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

• A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

• A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

• Clear the MIL and the DTC with a scan tool.

Diagnostic Aids
• Test for fuel contamination. Small amounts of water can be delivered to the fuel injectors and cause a lean exhaust indication. A lean exhaust indication can also be caused by too much alcohol in the fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

• The system will go lean if an injector is not supplying enough fuel.

• A lean condition could be present during high fuel demand due to a fuel pump that does not pump enough fuel, a plugged fuel filter, or a restricted fuel pipe.

• Review the Failure Records with a scan tool. If an intermittent condition is suspected, refer to Intermittent Conditions .