P0175 and P0172 OBD2 Codes on 2005 Dodge Durango 3.7L: Causes and Diagnosis
I own a 2005 Dodge Durango with a 3.7L engine. Recently, the vehicle began experiencing misfiring and hesitation during acceleration, along with a significant drop in fuel efficiency—down to half of what it was previously. The onboard diagnostics have revealed codes P0175 and P0172, both indicating rich air-fuel mixture conditions. I've already replaced several components including the thermostat, water pump, tension pulley, MAP sensor, spark plugs, coil packs, and oxygen sensors, but the issue persists. One potential cause listed in the diagnostic system is a malfunctioning MAF (Mass Air Flow) sensor. However, my 2005 Dodge Durango does not have a traditional MAF sensor—there is only a small sensor located on the back of the breather hose, and I'm unsure of its function. Given that all major engine components have been replaced or serviced, what other potential causes could be responsible for these P0175 and P0172 codes? Are there any common issues specific to this model year and engine that might explain the rich mixture readings?
P0172 and P0175 are related but indicate different fuel trim banks—both point to a rich air-fuel mixture. The easiest test is to check fuel pressure under normal conditions, then monitor for drop in pressure during KOEO (Key On, Engine Off) to assess injector performance or fuel pressure regulator function. Also verify spark at all plugs: inspect their color—black, wet, dry, or tan? NGK plugs are common. Ensure the thermostat used is 195°F. More info here: http://www.obd-codes.com/p0175