H1 CHECK FOR DTCS

Are DTCs P0171, P0172, P2195, P2196 or P219A present?

Yes	No
GO to H2.	RETURN to SYMPTOM CHARTS for further direction.

H2 RICH OR LEAN SYSTEM DTCS

NOTE: Do not clear the DTCs or reset the keep alive memory (KAM).

Access the PCM and record the CHT PID from the freeze frame data. The freeze frame data is used to recreate the concern.
Carry out the PCM self-test.

Are any DTCs present other than P0171, P0172, P2195, P2196 or P219A?

Yes	No
RETURN to SYMPTOM CHARTS for further direction.	GO to H3.

H3 CARRY OUT A VISUAL INSPECTION ON THE INTAKE AIR SYSTEM AND ALL VACUUM HOSES

Ignition OFF.
Check the air filter element and housing for blockage.
Inspect the entire air intake system for leaks such as:
- hoses connecting to the MAF sensor assembly
- cracked or punctured intake air tube
- loose connections on the intake air tube at the air cleaner housing or throttle body
- hoses connecting to the throttle body
- obstructions, restrictions, or damage
Check the throttle plate for obstructions or sludge.
Inspect the entire length of all vacuum hoses for:
- correct connections
- damage or cracks
- damaged or cracked vacuum tees
Inspect the intake manifold or gaskets for leaks.
Inspect the exhaust gas recirculation (EGR) system for leaks such as:
- EGR valve gasket leak to the intake manifold
Verify the integrity of the positive crankcase ventilation (PCV) system.
Verify the correct PCV valve part number.
Inspect the exhaust system for leaks at flanges and gaskets.
Visually inspect the HO2S for:
- pinched, shorted, and corroded wiring or pins
- oil or water contamination
- crossed sensor wires
Inspect for an incorrectly seated oil dipstick, dipstick tube, or oil fill cap.

Is a concern present?

Yes	No
For vacuum leak concerns, GO to H4. For all others, REPAIR as necessary. Clear the PCM DTCs. REPEAT the self-test.	GO to H4.

H4 CHECK FOR THE PRESENCE OF A VACUUM LEAK
NOTE: Fuel trim values at idle are more sensitive to a vacuum leak. The vacuum leak (unmetered air) represents a larger portion of the total air flow at idle than at part throttle.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Test Procedure