Test Description

The numbers below refer to the step numbers on the diagnostic table.

2: This step determines whether the fault is present.
4: Disconnecting the MAF sensor determines if the MAF sensor signal is skewed. If the Short Term FT parameter changes more than the specified value, there is a condition with the MAF sensor. A MAF sensor condition can cause this DTC without setting a MAF DTC. If there is a MAF sensor condition, the MAF sensor parameters will appear to be within range.

DTC P2178

Step	Action	Values	Yes	No
1	Did you perform the Diagnostic System Check - Vehicle?	-	Go to Step 2	Go to Diagnostic System Check - Vehicle
2	IMPORTANT: If any DTCs are set, except P2178, refer to those DTCs before proceeding with this diagnostic. Idle the engine at the normal operating temperature. The fuel system is in Closed Loop. Observe the Total Fuel Trim Avg. parameter with a scan tool. Is the Total Fuel Trim Avg. less than the specified value?	-22%	Go to Step 3	Go to Step 4
3	Observe the Freeze Frame and/or the Failure records data for this DTC. Turn the ignition OFF 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 and/or the Failure records data. Does the DTC fail this ignition cycle?	-	Go to Step 4	Go to Diagnostic Aids
4	Start the engine. IMPORTANT: Additional DTCs set with the mass air flow (MAF) sensor disconnected. Disconnect the MAF sensor harness connector while the engine is operating. Observe the Short Term FT parameter with a scan tool. Connect the MAF sensor after completing this step. Does the Short Term FT parameter change more than the specified value with the MAF sensor disconnected?	20%	Go to DTC P0101	Go to Step 5
5	Inspect for the following conditions: Inspect for a collapsed air intake duct. Inspect for a restricted air filter element. Refer to Air Cleaner Element Replacement . Inspect the MAF sensor for foreign objects. Refer to Mass Airflow Sensor/Intake Air Temperature Sensor Replacement . Inspect for restricted exhaust system. Refer to Symptoms - Engine Exhaust . Inspect for excessive fuel in the crankcase. Change the oil as necessary. Inspect for rich injectors. Refer to Fuel Injector Solenoid Coil Test Inspect for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (w/o Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (w/Special Tool) . Inspect the engine control grounds for being clean, tight, and in the correct locations. Inspect for an engine mechanical condition. Refer to Symptoms - Engine Mechanical . Did you find and correct the condition?	-	Go to Step 6	Go to Fuel System Diagnosis
6	Turn OFF the ignition for 30 seconds. Start the engine. Reset the fuel trim system with a scan tool. 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 7
7	Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed?	-	Go to Diagnostic Trouble Code (DTC) List - Vehicle	System OK