I've been throwing some lean codes every now and then, and when I pull the code right after it comes on, it reads 171 H. Does that mean it was a lean blip and is already history?

Let's say it reads 171 H C, that means it's current and still running lean?

 

Correct H = Historic and C = Current

Obviously it's just the Current ones you usually have to work on. The C5 will throw codes if you look at it the wrong way, but most are temporary and end up with an H quickly.

 

Thank you

 

Heres a description of the fault that might help:

DTC P0171 or P0174
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 and closed loop. During open loop, the PCM determines fuel delivery based on sensor signals without oxygen sensor input. During closed loop, the oxygen sensor inputs are added and used by the PCM to calculate short and long term fuel trim fuel delivery adjustments. If the oxygen sensors indicate a lean condition, fuel trim values will be above 0 percent. If the oxygen sensors indicate a rich condition, fuel trim values will be below 0 percent. Short term fuel trim values change rapidly in response to the heated oxygen sensor (HO2S) voltage signals. Long term fuel trim makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1. If the PCM detects an excessively lean condition, this DTC will set.
Conditions for Running the DTC

DTCs P0101, P0103, P0108, P0135, P0137, P0141, P0200, P0300, P0410, P0420, P0430, P0440, P0442, P0443, P0446, P0449, P0506, P0507 or P1441 are not set.
The engine coolant temperature (ECT) is between 75-115°C (167-239°F).
The intake air temperature (IAT) is between -20 and +90°C (4-194°F).
The manifold absolute pressure (MAP) is between 26-90 kPa (3.7-13 psi).
The vehicle speed is less than 137 km/h (85 mph).
The engine speed is between 400-3,000 RPM.
The barometric pressure (BARO) is more than 74 kPa (10.7 psi).
The mass airflow (MAF) is between 5-90 g/s.
The fuel level is more than 10 percent.
The throttle position (TP) is less than 90 percent.

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Conditions for Setting the DTC

The average long term fuel trim cell value is above 23 percent.
All of the above conditions are present for 6 seconds.

Diagnostic Aids

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.
Use a scan tool in order to review the Failure Records . If an intermittent condition is suspected, refer to Intermittent Conditions .


You might like to check the following systems which the book suggests checking to identify an intermittent P0171H

Perform a visual/physical inspection of the following items:

The wiring harness for damage or cuts
A misrouted harness that is too close to high voltage/high current devices such as secondary ignition components, motors and generators--These components may induce electrical noise on a circuit that may interfere with normal circuit operation.
The vacuum hoses for proper routing, connections, splits, or kinks
Air leaks at the throttle body mounting area, mass air flow sensor (MAF), and the intake manifold sealing surfaces
The MAF sensor installation--The arrows on the plastic portion of the sensor must point towards the engine.
The powertrain control module (PCM) and body grounds for being clean and tight
The battery connections for being clean and tight
The charging system for proper operation-- Refer to Charging System Test in Engine Electrical.