Now that UPS decided to get me the upstream oxygen sensor as well (I already had the downstream sensor), both Denso, I am ready to take the bull by the horns.
I appreciate the pictures posted by DWClapp but the even simpler understanding for me was his advice to take the route starting from black connector by the firewall by touch with fingers to get to downstream sensor location and, similarly, starting from the gray connector by the firewall to get to the upstream sensor location. This was Step number one.
Step number two is still waiting for the 7/8" tool from Harbor Freight Tools which I hopefully get by the end of this week. And of course to rent the slit socket from Advance Auto Parts.
Now if it doesn't bother you, nice gentlemen who did this sensors replacing, please help me with the most important step, Step number three: How to remove the thick cable blocking my hand access to Sensor 1 without disturbing or breaking anything?
PS: Does anybody know at what end of the sensor I should leave the portion of unwrapped wires (about 2.5", both sensors): the connector or the sensor.
Thank you.

 

Sensor plugs on firewall =

 

Thank you Dell for showing me the connectors location, which I said I knew (from Mr. DWClapp's pictures). I even found out, as I also said, --via fingers touching route-- where both sensors are. All I asked (and your picture doesn't show and your always omni-laconic comment misses) how to remove the thick cable above route to sensor 1 which is at the left of not shown in your connectors picture, so that I unscrew the Sensor 1 which I don't know what it covers inside its spiral 1.25" black electric(?) covering. Okay, I will find out by myself with a set of wrenches and feminine delicacy not to disturb anything.

 

I replaced all the sensors on my car. You should be able to replace all four sensors without moving cable around. You might be referring to one of the vacuum hoses near the top of the engine, which should be able to be pulled out by hand and moved to one side. Firewall side sensors are not easy to get to, but if you stay with it, you'll figure it out (I did and I have little patience for this stuff - but enjoy it nontheless).

 

Your question was about the portion of "unwrapped" wired to plug or sensor side. I figured a picture would be self explanatory. As far as getting room to work, you can CAREFULLY remove the brake booster line shown in the forefront of my pic, swing it up to the right CAREFULLY. You can also remove the coolant part in this video. You just need patience and care.

 

This is looking down toward the o2 sensor =

 

Yeah, this ugly thick hose crossing your pic above. I cannot just "move" it by hand as it is fastened all over the place in heavy metal shields. It bothers me to get down (a little arrow or highlight would have helped in your "looking down" p.o.v. picture. To me it seems that it is easier to remove the cowl (and the covered by it windshield wiper arms. Ooooffff.

 

Yeah, I watched another video where the guy removed the wiper cowl for a TINY bit more room. Working on a Jag is what it is (Bimmer wasn't any different). Engineers don't work on the cars, lol.

 

marcella: Yes, there is a thick bundle of wires wrapped in black tape running sideways behind the engine, between the intake manifold and firewall, aka bulkhead. I did not move this thick wiring harness to replaced the bank 1 downstream oxygen sensor. Instead, I stood by the front US passenger tire and squeezed my left hand and forearm between the engine and the firewall, under that thick wiring harness, to reach the downstream oxygen sensor. Yes, it's a tight squeeze, but there's enough room to snake your hand in and slip the 7/8 inch slotted socket over the downstream oxygen sensor. I also used my left hand to snap the articulated Harbor Freight socket wrench into the slotted 7/8 inch socket, with the socket wrench handle extending upward, between the firewall and intake manifold. https://www.harborfreight.com/t-bar-...het-98484.html
With my right hand, I pushed the handle of the socket wrench away from me, turning the sensor counter-clockwise to unscrew it, while keeping my left hand behind the engine, on the socket so it stayed on the sensor as it unscrewed. There's just enough room for the handle of the socket wrench to slide sideways between the cowling below the windshield and the intake manifold. Once the sensor loosened a little, I removed the socket wrench and continued to unscrewed the sensor with my left fingers (still snaked behind the engine), using my right hand to hold the sensor's wires high enough so they would not twist and tangle as I unscrewed the sensor with my left hand.

You may find it difficult to slide the slotted 7/8 inch socket over the oxygen sensor, because the shiny aluminum heat shield may be close to the sensor. No worries - simply bend that heat shield enough, say an ~1/8 inch or so away from the sensor, using your fingers or a flat blade screw driver, until there's enough gap for the 7/8 inch slotted socket to slide over the sensor.

Regarding the protective covering over the sensor wires, slide that covering away from the sensor's electrical connector until it fully covers the wires into the sensor. This protective covering is a heat shield so the wires near the sensor are not directly exposed to the heat of the catalytic converter.

It takes some patience and persistence, but it's doable.

 

THANK YOU SO VERY MUCH. The heat shield was (worryingly?) distanced from the sensor. Should I try to stick it to the sensor after I install the new one?
Also the DENSO technical support reported me meantime how to distinguish the genuine Denso sensors and told me that they did not give authorization to Amazon to sell their products. As per the length of the wires, their diagram shows the actual length prolonging inside the sensor and the connector to a total of the 21.6" (540mm). My only remaining worry is that I put the bag with one of the sensors on the glass top of my computer desktop yesterday kind of banging it on the glass (slightly but however). Did I damage it (they say to handling of sensors should be very careful not to drop them)?
Thanks for telling me not to remove the cowl to spare me for another expense for that wiper arms removal tool (it does not work otherwise).
The Harbor Freight ratchet wrench only comes at the end of the week (when it --oh, boy, doesn't it give us a break?-- thunderstorms again, for the whole rest of July not letting me work outside). I was hoping that the upstream sensor could be maneuvered without that tool, just a 7/8" wrench, but I cannot get to that sensor from the passenger side with my probably shorter than yours, hand, the access to the upstream sensor being much easier from the driver side. I will keep you posted how everything worked. Again, thanks, thanks, thanks.
______________________
PS. What wires are inside that ugly bulkhead?

 

marcela: If you need to bend the heat shield slightly to get the socket over the oxygen sensor, there's no need to bend it back into position after you install the new sensor, since you're bending it only a ~1/8 inch or so.

You probably did not damage the new oxygen sensor when you banged it slightly on the glass table top. They are designed to withstand a lot of engine vibrations and intense heat for ~100K miles, so they can't be fragile.

The thick bundle of wires is the engine's wiring harness. It contains many small wires which connect the engine's numerous sensors to the engine's computer to monitor and control the engine.

 

No matter how many steps and diligence I followed to get to the location of the old sensor and how many tools I got, I stumbled on this evil wall of my enterprise: the old sensor devilishly stubbornly refusing to get out from its port! It doesn't give a dime on my DW40 and repeats. Just stays there. Is my arm too weak or do mechanics have special tricks (such as cutting the wires of the old sensor which is not recommended until a comparison with the new one)? Oooff and Ouch....