I kept getting the P0171 system too lean bank 1 code so I thought I would try changing o2 sensors and maf sensor to see if it would fix my problem. I did it last saturday drove to vegas and back but code still present so to be continued. I did take pictures and had to do some cross referencing on part no. between oem denso toyota and Denso parts so I have included that info as well. I bought all 4 sensors and have replaced three of the four. I still haven't figured out the best way to get to to Bank 2 Sensor 1
Step by step (remove battery terminal so reading resets)
1.Disconnect MAF sensor and hoses connected air box
2. Loosen screw on retainer clip to loosen hose connected to throttle body
3. First O2 sensor now visible and with crows feet socket you remove.
4. Jack up car from left side of front passenger tire. Insert jack-stand.
5. Insert 2nd jack stand on front side tow hook.
6. From behind front passenger tire you can access the lower o2 sensor for bank one.
7. Unplug harness from above this is on side wall then get back under car to loosen and remove
8.Next O2 wires are reached by lifting carpet on front passenger side floor. The actual clip is on side wall of center console.
9. While under car open up clip holding the wire along undercarriage and also loosen rubber grommet on floor.
10. Loosen O2 sensor and use small clamp from old wire on new wire right below rubber grommet
This is instructions for the 3 of the 4 sensors I could easily reach.
The link has pictures with text labels for locations
These part numbers only apply for 98 99 from what I have read
B1S1=89465-30430 = Denso 234-4048 easiest to replace once all pipes up to throttle body are removed
B1S2=89465-30440 = Denso 234-4626 best access from under wheel well. you can see from above but easier to take out from below.
B2S1=89465-30470 = Denso 234-4630 not yet done
B2S2=89465-30450 =Denso 234-4603 under passenger seat. connector is at center console and rubber grommet is under pasenger floormat and carpet
234 4048 55.55
234 4626 60.03
234 4630 $65.58
234 4603 $58.09
Current Amazon prices ~240 shipped
I used jack stands under front passenger tire and then on the tow hook on passenger side.
This was a must to get to B1S2 and made easier to do B2S2. I sprayed them all with PB Penetrating Catalyst/WD40 type of product. I used half inch socket rotating head and the crows feet.
cross reference for toyota to denso is for 98-99 is on page 497