Diagnostic Aids

WARNING: This page is about a different car, the 2004 Pontiac Grand Prix. However, it is still accessible from the selected car via links, so may be relevant.

A malfunctioning MAF sensor can cause a rich condition and set this DTC.
If an intermittent condition is suspected, refer to Intermittent Conditions .

DTC P0172

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	Are any DTCs other than DTC P0172 also set?	or	Go to Diagnostic Trouble Code (DTC) List	Go to Step 3
3	Install the scan tool. Turn ON the ignition. Observe the Freeze Frame/Failure Records parameter with a scan tool and record the displayed data for this DTC. Start and idle the engine at the normal operating temperature in Closed Loop. Observe the Long Term FT parameter. Does the scan tool indicate that the Long Term fuel trim is less than the specified value?	-24%	Go to Step 4	Go to Diagnostic Aids
4	Observe HO2S 1 and HO2S 2 parameters with a scan tool. Does the scan tool indicate that the heated oxygen sensor (HO2S) voltages 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: The inlet screen of the mass airflow (MAF) sensor for blockage-Refer to Mass Air Flow (MAF)/Intake Air Temperature (IAT) Sensor Replacement . Vacuum hoses for splits, kinks, and proper connections-Refer to Emission Hose Routing Diagram (L26/L32) . The air intake duct for being collapsed or restricted-Refer to Air Cleaner Intake Duct Replacement . The air filter for being dirty or restricted-Refer to Air Cleaner Element Replacement . Objects blocking the throttle body-Refer to Throttle Body Assembly Replacement (L26) or Throttle Body Assembly Replacement (L32) . Did you find and correct the condition?	-	Go to Step 9	Go to Step 8
6	Turn OFF the engine Visually and physically inspect the following items: The HO2S for proper installation-Refer to Heated Oxygen Sensor Replacement - Position 1 and Heated Oxygen Sensor Replacement - Position 2 . Ensure that the electrical connectors and wires are secured and not contacting the exhaust system. Did you find and correct the condition?	-	Go to Step 9	Go to Step 7
7	Test for short between the signal circuit and the low reference circuit or ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 9	Go to Fuel System Diagnosis
8	Inspect for the following: Excessive fuel in the crankcase Saturated evaporative canister, stuck purge valve or fuel cap not sealing Excessive fuel pressure-Refer to Fuel System Diagnosis . Properly functioning fuel injectors-Refer to Fuel Injector Coil Test . Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) . Did you find and correct the condition?	-	Go to Step 9	Go to Symptoms - Engine Mechanical in Engine Mechanical
9	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 in 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 10
10	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