Diagnostic Aids
WARNING: This page is about a different variant/trim than selected.
- Excessive resistance in the fuel injector control and/or the ignition 1 voltage circuits may cause the following symptoms:
- A lean condition
- Misfire
- Rough idle
Refer to DTC P0200 .
- The system may become lean if an injector is not suppling enough fuel.
- A lean condition could be present during high fuel demand.
- Review the Failure Records with a scan tool. If an intermittent condition is suspected, refer to Testing for Intermittent Conditions and Poor Connections
.
DTC P0171 or P0174
| 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 DTC P0171 or P0174 also set? |
- |
Go to Diagnostic Trouble Code (DTC) List - Vehicle |
Go to Step 3 |
| 3 |
- Install the scan tool.
- Start and idle the engine at the normal operating temperature in Closed Loop.
- Record the long term fuel trim.
- Turn OFF the engine.
- Turn ON ignition, with the engine OFF.
- Review the Freeze Frame/Failure Records and record the displayed data for this DTC.
Does the scan tool indicate that the long term fuel trim is greater than the specified value? |
24% |
Go to Step 4 |
Go to Diagnostic Aids |
| 4 |
- Operate the engine at idle.
- Observe the HO2S parameters with a scan tool.
Does the scan tool indicate that the parameter is 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 8 |
Go to Step 7 |
| 6 |
- Turn OFF the engine.
- Inspect the heated oxygen sensor (HO2S) for proper installation.
- Verify the electrical connectors and the wires are secure, and not contacting the exhaust system.
- Test for continuity between the HO2S signal circuit and the low reference circuit. Refer to the following:
Did you find and correct the condition? |
- |
Go to Step 8 |
Go to Fuel System Diagnosis |
| 7 |
- Operate the engine at idle.
- Inspect for any missing, loose, or leaking exhaust components forward of the HO2S.
- Inspect for vacuum leaks at the intake manifold, throttle body, and injector O-rings.
- Inspect the air induction system and the air intake ducts for leaks.
- Inspect the secondary air injection (AIR) system for leaks, improper air delivery, and for the shut-off valves not closing.
- Inspect the crankcase ventilation system for leaks. Refer to Crankcase Ventilation System Inspection/Diagnosis
.
- The evaporative emission (EVAP) lines and components for damage or blockage-Refer to Evaporative Emissions (EVAP) Hose Routing Diagram
.
- Inspect the vacuum brake booster for leaks.
Did you find and correct the condition? |
- |
Go to Step 8 |
Go to Symptoms - Engine Mechanical |
| 8 |
IMPORTANT:
After repairs, use the scan tool Fuel Trim Reset function to reset the Long Term Fuel Trim.
- Turn ON the ignition, with the engine OFF.
- 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 - Vehicle |
System OK |