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DTC P0172 Fuel Trim System Too Rich: Troubleshooting

TROUBLESHOOTING CHART

Step Action Value(s) Yes No
1 Perform an On-Board Diagnostic (OBD II) System Check.
Was the check performed?		 - Go to Step 2 Go to "ON-BOARD DIAGNOSTIC (OBD II) SYSTEM CHECK :"
2
  1. Install the scan tool to the Data Link Connector (DLC).
  2. Turn the ignition ON.

Are any component related Diagnostic Trouble Codes (DTCs) set?		 - Go to APPLICABLE DTC TABLE  Go to Step 3
3 With the engine running, operate the vehicle until the LOOP STATUS indicates closed.
Is the Long Term Fuel Trim value above the specified value?		 -20% Go to Step 4 Go to Step 5
4
  1. Turn the ignition switch ON, with the engine OFF.
  2. Review the Freeze Frame data and note the parameters.
  3. Operate the vehicle within the Freeze Frame conditions and Conditions for Setting The DTC as noted.

Does the Long Term Fuel Trim value above the specified value while operating under the specified conditions?		 -20% Go to Step 20 Go to Step 5
5 Visually/physically check the air cleaner filter for excessive dirt or being plugged and repair as needed.
Is the repair complete?		 - Go to Step 20 Go to Step 6
6 Visually/physically check the air intake system for collapsed or restricted and repair as needed.
Is the repair complete?		 - Go to Step 20 Go to Step 7
7 Inspect the throttle body inlet for damaged or foreign objects which may partially block the airflow and repair as needed.
Is the repair complete?		 - Go to Step 20 Go to Step 8
8
  1. Turn the ignition OFF.
  2. Inspect the throttle bore, throttle plate and Idle Air Control (IAC) passages for clocking and foreign objects and repair as needed.

Is the repair complete?		 - Go to Step 20 Go to Step 9
9 Start the engine with the vehicle in park or neutral and A/C off and note the idle quality.
Is a low or unsteady idle being experienced?		 - Go to Step 10 Go to Step 12
10 Idle the engine.
Are the IAC counts below the specified value?		 100 Go to Step 12 Go to Step 11
11
  1. Turn the ignition OFF.
  2. Disconnect the Manifold Absolute Pressure (MAP) sensor electrical connector.
  3. Start the engine.
  4. Operate the vehicle in Closed Loop while monitoring the Long Term Fuel Trim value.

Does the Long Term Fuel Trim value increase above the specified value?		 -20% Go to Step 19 Go to Step 12
12 Check the IAC valve performance. Refer to "DTC P0506 IDLE SPEED RPM LOWER THAN DESIRED IDLE SPEED :" or "DTC P0507 IDLE SPEED RPM HIGHER THAN DESIRED IDLE SPEED :" and repair as necessary.
Is the repair complete?		 - Go to Step 20 Go to Step 13
13
  1. Turn the ignition ON.
  2. Slowly press the acceleration pedal.

Does the Throttle Position (TP) sensor display increase steady and evenly from its minimum voltage at closed throttle to its maximum voltage at Wide-Open Throttle (WOT)?		 - Go to Step 14 Go to Step 18
14
  1. Perform the Fuel System Diagnosis.
  2. If the table isolate a problem, repair as needed.

Is the repair complete?		 - Go to Step 20 Go to Step 15
15
  1. Perform the Evaporative Emission (EVAP) Control System Diagnosis.
  2. If the table isolate a problem, repair as needed.

Is the repair complete?		 - Go to Step 20 Go to Step 16
16
  1. Perform the Fuel Injector Balance Test.
  2. If the table isolate a problem, repair as needed.

Is the repair complete?		 - Go to Step 20 Go to Step 17
17
  1. Remove the Oxygen sensor 1 (O2S1).
  2. Visually/physically inspect the O2S1 for silicone contamination.
    NOTE: This will be indicated by a powdery white deposit on the portion of the O2S1 exposed to the exhaust stream.
  3. If contamination is present on the O2S1, find the source and repair as needed.

Is the repair complete?		 - Go to Step 20 Go to "DIAGNOSTIC AIDS :"
18
  1. Check the TP sensor mounting screws.
  2. If they are too loose or missing tighten or replace them as needed.
  3. If the screws are OK, replace the TP sensor.

Is the repair complete?		 - Go to Step 20 -
19
  1. Turn the ignition OFF.
  2. Replace the MAP sensor.

Is the repair complete?		 - Go to Step 20 -
20
  1. Using the scan tool, clear the Diagnostic Trouble Codes (DTCs).
  2. Start the engine and idle at normal operating temperature.
  3. Operate the vehicle within the Conditions for setting this DTC as specified in the supporting text.

Does the scan tool indicate that this diagnostic has run and passed?		 - Go to Step 21 Go to Step 2
21 Check if any additional DTCs are set.
Are any DTCs displayed that have not been diagnosed?		 - Go to APPLICABLE DTC TABLE  System OK
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