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PO 174 Code on 1998 Ford Expedition 4.6L: Causes, Diagnosis & Fixes

Model: 98 Expedition Fault Code: P0174 Posted: 2006-04-26 14:34

I own a 1998 Ford Expedition with 105,000 miles that has recently triggered the PO 174 diagnostic code (System Too Lean Bank 2). I cleared the code, but it returned within a few days. I suspect the driver's side front oxygen sensor is faulty. Before replacing any parts, I'd like to get expert advice on this issue. The truck runs smoothly and has no noticeable performance issues. I recently added injector cleaner to the fuel system. Thanks, Ed

Related fault codes

P0174

Comments (3)

Anonymous 2006-04-26 17:08

The check engine light likely came on either before or after using the injector cleaner. Have you checked your Mass Air Flow (MAF) sensor? Look for vacuum leaks around the intake manifold—this is one of the most common issues reported on Ford vehicles this month. While an oxygen sensor can cause PO 174, there are many other potential causes to rule out first. Good luck and please keep us updated. Jeff

Anonymous 2006-05-15 14:55

I cleaned my MAF sensor, replaced both the air filter and gas filter. The truck still runs well, but the PO 17-than code keeps returning. My next step is to perform a vacuum leak test by spraying brake cleaner around the intake manifold and listening for an engine 'race' sound. Do you have any other suggestions? Ed

Anonymous 2006-05-15 16:01

Without seeing the vehicle in person, I don't have additional ideas beyond what we discussed earlier—oxygen sensors can trigger PO 174, but many Ford owners with PO 171 or PO 174 issues report that replacing the intake gasket resolves the problem. I just inspected another 1998 Expedition at my shop this weekend—the idle remained stable, but fuel trim values changed when we sprayed around the intake. It might be a simple PCV hose issue instead. Good luck and please keep us posted. Jeff