Test Description
The number below refers to the step number on the diagnostic table.
- 8:
If conditions were not corrected, a worn cam, worn intake or exhaust valves, or other engine mechanical failures may be at fault.
DTC P0171
| 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 |
Are any DTCs other than P0171 also set? |
- |
Go to Diagnostic Trouble Code (DTC) List - Vehicle |
Go to Step 3 |
| 3 |
- Install a scan tool.
- Review the Freeze Frame/Failure Records and record the displayed data for this DTC.
- Select the Fuel and Emission data list.
- Start the engine.
- Observe the Long Term FT parameter with a scan tool.
Is the Long Term FT parameter more than the specified value? |
19% |
Go to Step 4 |
Go to Diagnostic Aids |
| 4 |
- Operate the engine at idle.
- Observe the Heated Oxygen Sensor (HO2S) parameters with a scan tool.
Does the scan tool indicate that the HO2S parameters 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:
Did you find and correct the condition? |
- |
Go to Step 9 |
Go to Step 8 |
| 6 |
- Turn OFF the engine.
- Turn ON the ignition, with the engine OFF.
- Observe the manifold absolute pressure (MAP) sensor pressure parameter with a scan tool.
- The MAP sensor pressure should be within the range specified for your altitude. Refer to Altitude vs Barometric Pressure
.
Do the MAP parameters indicate the correct barometric pressure? |
- |
Go to Step 7 |
Go to DTC P0106 |
| 7 |
- Turn OFF the engine.
- Inspect for the following conditions:
- Proper HO2S installation
- Electrical connectors and wires are secured and not contacting the exhaust system
- An open or a short to ground in the HO2S signal circuit
Did you find and correct the condition? |
- |
Go to Step 9 |
Go to Fuel System Diagnosis |
| 8 |
- Operate the engine at idle.
- Inspect for the following conditions:
- Secondary air injection (AIR) shut-off valve stuck open
- Missing, loose, or leaking exhaust components
- Vacuum leaks at the intake manifold, throttle body, and injector O-rings
- Leaks at the air intake ducts
- Leaking crankcase ventilation system
Did you find and correct the condition? |
- |
Go to Step 9 |
Go to Symptoms - Engine Mechanical |
| 9 |
IMPORTANT:
After repairs, use the scan tool Fuel Trim Reset function in order to reset the Long Term Fuel Trim.
- Turn ON the ignition, with the engine OFF.
IMPORTANT:
DO NOT clear codes with the engine running. The codes may reset in the same ignition cycle.
- 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 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 - Vehicle |
System OK |