Ok, I have an 03 ram with Federal Emissions package. 1 (one) catalytic convertor & one upstream and 1 downstream 02 sensor. Since I have 140,000 miles, think it's time to change the sensors, getting intermittent P0420 codes. I order the parts...

NTK Oxygen Sensor
Oxygen Sensor 23556 Post-Cat Right Exc. Calif.
Oxygen Sensor 23527 Pre-Cat Right Exc. Calif.

I uploaded an image.

Low and behold the post cat 02 sensor fits perfectly, but when I go to change the pre-cat, the connector is the same as the post cat! I am completely baffled. Should I order another post cat and install that one?

2003 DODGE RAM 1500 QUAD CAB PICKUP
Make: DODGE
Model: RAM 1500
Trim: ST Quad Cab
Color: BLACK
Engine: 4.7L
Fuel: Gasoline
Transmission: 5-Speed Manual
Drive: RWD
3.55 Rear Axle Ratio
Corporate 9.25 LD Rear Axle
Two Wheel Drive (2WD)/(4X2)
6 FT. Cargo Box

 

Not the same. They gave you the wrong part.

 

There may be a difference halfway through the year or something. Verify 2002 and 2004 to see if you can match to yours.

 

All 4 of my 02 sensors share the same connector.

 

Sure, I ordered another Oxygen Sensor 23556, same as the post cat. It fit and drove on highway for 40 minutes and checked my scan tool and I am ready for emissions testing (next year )

So, in summary, both 02 sensors are the exact same part, I assume the computer uses them differently.

Why the online fit guides were misleading me, I don't know, but this part was actually slightly cheaper and more importantly it works.

Like dirtydog said, there must be subtle manufacturing change in my model, but to everyone that posted, thanks for all your help!

 

I just checked AdvanceAuto's website
http://shop.advanceautoparts.com/p/n...=oxygen+sensor

It actually looks like the other part number is what fits both up and down depending on Cailornia Emissions standards.

odd.