2002 C5 P0171 Error Code

[David B.]

Our low mileage 2002 C5 LS1 will display "check engine" light as a result of a P0171 error code. left bank lean error, every 50-100 miles. Reset code, check engine light cleared. Code always shows as "history" not "current." Have checked, visually, for vacuum leaks, cleaned mass air flow and throttle body. Other potential causes are beyond my ability to check (oxygen sensors, fuel filter, fuel pump, etc.). Has anyone had this problem and what was the solution? I do have a GM Corvette certified mechanic appointment but must wait four weeks. Thanks in advance... Dave

[Richard M.]

Re: 2002 C5 P0171 Error Code

David I poked around CF C5/C6 sections and many things could cause it, but one owner found a bad coil wire/bad coil and that solved it. Here

Try Advanced Search there using P0171 as the search string. Lots of info.

e.g. Here but it will disappear in a few hours.
https://www.corvetteforum.com/forums...rchid=90343614

Rich

[Edward J.]

Re: 2002 C5 P0171 Error Code

Dave have you checked the PCV hose sometime they will clasp,and just a small hole in hose will cause the computer to add fuel. The hose I think goes from the pass.side valve cover to the plastic intake. If all looks good I suspect you may have a bad O2 sensor on-that bank.without the scan tool it would only be a guess. Age the car gets a few miles on them the sensor will slow down and of make correct adjustments. Since your only dealing with one bank fuel pressure and airflow are not a problem.vacuum leaks are rare,but not impossible.

[John D.]

Re: 2002 C5 P0171 Error Code

2002 Chevrolet Corvette

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Corvette VIN Y Service Manual

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Document ID: 776154

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DTC P0171 or P0174
Circuit DescriptionThe 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
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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.

Test DescriptionThe numbers below refer to the step numbers on the diagnostic table.

1. If the conditions were not corrected, refer to Fuel System Diagnosis for a possible fuel problem.
2. If the conditions were not corrected, a worn cam, worn intake or exhaust valves, or other engine mechanical failure may be the problem.

3	Operate the engine at idle. Observe the HO2S parameter with a scan tool. Step 4	Go to Step 5
4	Turn OFF the engine. Visually and physically inspect the following items: The vacuum hoses for splits, kinks, and proper connections. Refer to Emission Hose Routing Diagram. Ensure that the vehicle has sufficient fuel in the tank. If the fuel pressure is too low this DTC may set. Refer to Fuel System Diagnosis. Fuel contamination. Refer to Alcohol/Contaminants-in-Fuel Diagnosis. Step 7	Go to Step 6
5	Turn OFF the engine. Check the HO2S for proper installation. Ensure that the electrical connectors and the wires are secure and not contacting the exhaust system. Check for a short between the signal circuit and the low reference circuit. Step 7	Go to Fuel System Diagnosis
6	Operate the engine at idle. Check for any missing, loose, or leaking exhaust components forward of the HO2S. Check for vacuum leaks at the intake manifold, throttle body, and injector O-rings. Check the air induction system and the air intake ducts for leaks. Check the AIR system for leaks, improper air delivery, and for the shut-off valves not closing. Check the crankcase ventilation system for leaks. Refer to Crankcase Ventilation System Inspection/Diagnosis in Engine Mechanical. Step 7	Go to Symptoms - Engine Mechanical in Engine Mechanical
7	[COLOR=brown !important]Important: After any of the above repairs, use the scan tool Fuel Trim Reset function in order to reset the Long Term Fuel Trim. [/COLOR] Use a scan tool in order to clear the DTCs. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC, as specified in the supporting text. Step 8	Go to Step 2Diagnostic Trouble Code (DTC) List	System OK

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[David B.]

Re: 2002 C5 P0171 Error Code

Dave have you checked the PCV hose sometime they will clasp,and just a small hole in hose will cause the computer to add fuel. The hose I think goes from the pass.side valve cover to the plastic intake. If all looks good I suspect you may have a bad O2 sensor on-that bank without the scan tool it would only be a guess. Age the car gets a few miles on them the sensor will slow down and of make correct adjustments. Since your only dealing with one bank fuel pressure and airflow are not a problem.vacuum leaks are rare,but not impossible.

Ed, thanks. I did replace the PCV valve and checked hose, all good. Just had a P0174 code thrown, right bank lean error. Engine runs perfect giving no indication of a fault. I suspect a vacuum leak or fuel delivery problem which would explain both banks showing lean error. I do need a complete diagnostic scan to isolate the culprit. Yep, low mileage car purchased last fall, working out the 21 year old low mileage car bugs. Thanks... Dave

[David B.]

Re: 2002 C5 P0171 Error Code

Problem solved! Replaced mass air flow sensor (Delphi) and check engine light and error codes 0171 and 0174 gone. After all recommendations tried, I did have a Corvette certified mechanic perform a diagnostic test and he suggested replacing the after market Granatelli mass air flow sensor with a stock one (after market air flow sensor has been on the car for 19 years without a problem). He suggested that the after market sensor does little for horsepower improvement and that it would not be missed. Thanks for feedback everyone...