Bank 1 & 2 O2 Sensor ‘03 4.0L

[Shobo]

Hi everyone! I’m going to attempt to replace the O2 sensors on my sister-in-law’s ‘03 Explorer 4.0L. The dealership used a code reader and advised that the bank 1 & 2 O2 sensors were bad. I don’t have the code. I’m wondering if those are upstream sensors or downstream? Also, I have never replaced an O2 sensor, do I need any special tools? Thanks!

 

[imp]

Hi everyone! I’m going to attempt to replace the O2 sensors on my sister-in-law’s ‘03 Explorer 4.0L. The dealership used a code reader and advised that the bank 1 & 2 O2 sensors were bad. I don’t have the code. I’m wondering if those are upstream sensors or downstream? Also, I have never replaced an O2 sensor, do I need any special tools? Thanks!

There are 4 O2 Sensors, one at either end of the cat converters. The RH side rear sensor, the "downstream" will require removal of a sheet metal heat shield held in place by 3 bolts. No big deal. The connectors are difficult to reach to release the little "latch" on each, which allows them to come apart.

Note that the FRONT or UPSTREAM sensors are DIFFERENT from the rear, or downstream sensors. Your old ones, if original Ford, will have locating lugs on them which prevent using a front in rear and vice versa. MANY replacement sensors have NO LUGS, so you could easily place one in the wrong location. Watch that fact closely, as the APPEARANCE of the sensor head of the replacements may not match the old exactly. Tool needed, 7/8" open end wrench, I use a long screwdriver to depress the latch tang on the connector to allow disconnection. You may need to pry the connector(s) loose from their mounting, a plastic push-pin secures them to the body. After replacement, be certain no wiring can move about and come even close to the exhaust pipe or cat. imp

 

[lincolnshibuya]

don't shoot the messenger, just because you're getting an O2 sensor code it means that it's defective. Go to a parts store and have them scan the code, worst case is you have a new O2 sensor and code is still there.

 

[Drewmcg]

These are tricky to get out, especially w/o lift. There are kits available on amazon.com, e.g., https://www.amazon.com/Generic-Oxyg...UTF8&qid=1506129756&sr=8-13&keywords=O2+tools . But as Imp suggests you may be able to get out with an open end 7/8" or 22mm wrench. Soak that sucker with PB blaster, too.

You do need to figure out which sensors are bad before replacing. NB: The front (upstream) sensors do all the heavy lifting (providing PCM with info to adjust fuel trims). The rears are really there just to test the efficiency of each cat.

 

[imp]

"But as Imp suggests you may be able to get out with an open end 7/8" or 22mm wrench. Soak that sucker with PB blaster, too."

I used a 7/8" combination wrench, Craftsman, and had to "nudge" it on the box end with a light rubber hammer on one of the sensors. The others loosened with lots of hand force applied. imp

 

[Shobo]

Thank you all for the info. I don’t have access to a lift, so it might be an interesting job lol.

 

[TechGuru]

I've never used it on the Explorer so I have no idea if it would help but I have one of these that I've used on other vehicles.