1998 Ford Expedition OBD codes 171 and 174

Hi there,

Thank you for the donation.

These codes indicate lean mixture for both banks, so the first thing I would be looking at is the inlet manifold, I think we may be looking for something that is affecting both banks at the same time, a small vacuum hose off will not do this.

Mark (mhpautos)

Lean fuel condition can be caused by the following.

1. Vacuum leaks
2. EGR and PCV valve.
3. Low fuel pressure.
4. Dirty fuel injectors.
5. Mass Air Flow Sensor.
6. Oxygen sensor

Clean the MAF sensor and test the EGR-DPFE sensor