Diagnostic Aids

WARNING: This page is about a different variant/trim than selected.

A skewed mass air flow (MAF) sensor may set this DTC. Refer to DTC P0101 .
The system will go lean if an injector is not suppling enough fuel.
The system will go lean during high fuel demand.
Review the Failure Records with a scan tool. If an intermittent condition is suspected, refer to Intermittent Conditions .

DTC P0171 or P0174

Step	Action	Values	Yes	No
1	Did you perform the Diagnostic System Check-Engine Controls?	-	Go to Step 2	Go to Diagnostic System Check - Engine Controls
2	IMPORTANT: If any DTCs are set, other than P0171 or P0174, refer to those DTCs before continuing. Install the scan tool. Start the engine. Operate the vehicle within the Conditions for Running the DTC. Record the LT FT Cruise/Acce and LT FT Idle/Decel. parameter values. Turn OFF the engine. Turn ON the ignition, with the engine OFF. Review the Freeze Frame/Failure Records and record displayed data for this DTC. Does the scan tool indicate that the LT FT Cruise/Acce. parameter is more than the specified value?	23%	Go to Step 4	Go to Step 3
3	Does the scan tool indicate that the LT FT Idle/Decel. parameter is more than the specified value?	8.5%	Go to Step 4	Go to Diagnostic Aids
4	Operate engine at idle. Observe the front heated oxygen sensor (HO2S) parameters with a scan tool. Does the scan tool indicate that the values are within the specified range and fluctuating?	200-800 mV	Go to Step 5	Go to Step 6
5	Turn OFF the engine. Visually and physically inspect the following items: Vacuum hoses for splits, kinks, and proper connections-Refer to Emission Hose Routing Diagram . Ensure that the vehicle has sufficient fuel. If fuel pressure is too low this DTC may set. Refer to Fuel System Diagnosis . Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (w/o Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (w/Special Tool) . Did you find and correct the condition?	-	Go to Step 8	Go to Step 7
6	Turn OFF the engine. Inspect the HO2S for proper installation. Verify that the electrical connectors and wires are secured and not contacting the exhaust system. Did you find and correct the condition?	-	Go to Step 8	Go to Fuel System Diagnosis
7	Operate the engine at idle. Inspect for the following conditions: Missing, loose, or leaking exhaust components-Refer to Exhaust Leakage in Engine Exhaust. Vacuum leaks at the intake manifold and injector O-rings The air induction system and air intake ducts for vacuum leaks. The crankcase ventilation system for leaks-Refer to Crankcase Ventilation System Inspection/Diagnosis in Engine Mechanical. A skewed mass air flow (MAF) sensor-Refer to DTC P0101 . Did you find and correct the condition?	-	Go to Step 8	Go to Symptoms - Engine Mechanical in Engine Mechanical
8	IMPORTANT: After repairs, use the scan tool Fuel Trim Reset function in order to reset the Long Term fuel. Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition	-	Go to Step 2	Go to Step 9
9	Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed?	-	Go to Diagnostic Trouble Code (DTC) List	System OK