Re: Oxygen Sensor Part Number and Location
My 2001 2WD Sequoia MIL (Check Engine Light) has been lit for two years. Always got the same answer every time I had dealer check it out. Young punk newbie service techs always told me I needed all new catalytic converters and oxygen sensors for around $2,000. When I would ask why they would always say the diagnostics said so ($89 diagnostic fee with no real physical inspection or experience-based knowledge). I knew they were wrong (catalytic converters should last a couple of hundred thousand miles at least).
The other day I had the Sequoia down to install trailer brake controller and a 7-pin trailer plug. I saw Autozone had a $39 ODBII computer scanner at so I bought it and re-checked codes (420, 430 etc..) The OBDII codes (B4 and after new scanner) were always emissions related. Finally decided to do it myself by installing all new oxygen sensors (4), consisting of two new Toyota (Denso) OEM after-cat oxygen sensors (p/n 8946509300) (bank 2) and two new Denso before-cat oxygen sensors (p/n 234-4209) (bank 1). Also installed all new Denso PK20R8 double-platinum spark plugs (p/n 3127) (.032 gap). Toyota OEM Bank 2 sensors bought from Autonation (Parts.com). Spark plugs and Bank 1 sensors bought from sparkplugs.com. Total cost of sensors was around $250 for both sets. Same parts at local dealer would have approached $700. The non-OEM pre-cat versions required plug splicing (wire colors all match) but no big deal. Looked identical to removed OEM versions (Denso). I steered away from Bosch products and stuck to Denso (like Toyota does) after reading posts here on TS.
The Denso replacements from Sparkplugs.com came with copper anti-seize compound and it only took about 1/2 a tube to apply to both pre-cat sensor threads and 8 spark plug threads. Rear sensors use gaskets and don't thread in so no anti-seize used there. Still have a whole tube unopened left over. Be careful to not get any anti-seize compound near the business end of things to avoid fouling of the component (I always apply up to but not past the first two threads to make sure).
I borrowed a O2 sensor removal kit from Autozone (deposit required). I also sprayed all old sensors with PB Blaster penetrant the day before (Kroil penetrant would be as good or better). I was stunned how easily it was to remove the front sensors from the threaded bungs. The electrical plugs were actually harder. The front sensors that re-used the spliced original electrical plugs snapped right in to the chasis electrical recepticles nicely. I did find the rear after-cat Toyota OEM replacement sensors hard to plug back in to the chasis electrical harness. I fished the red silicon gaskets out of the chasis recepticles and shaved one segment off them with a razor blade and then reinstalled them. Then the new rear sensor plugs snapped in without a problem.
Added 2 bottles of Chevron Techron fuel additive to fuel tank and filled tank with premium fuel (have the common sticking fuel sender problem). Cleared diagnostics codes related to emissions with the ODBII scanner. After 1,000 miles including towing MIL does not light. Mileage and power have improved and engine runs like a sewing machine and fuel gauge behaves (due to Techron, not other work).
P.S. The only reason Toyota uses two part numbers for the OEM pre-cat sensors is due to difference in wire lengths. Not an issue when splicing your own. I left a little extra length in the spliced harness assemblies for future servicing. I also cut off and kept the plugs from the after-cat original sensors and stored them away in case I ever need them.
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Last edited by jliltd; 03-24-2008 at 10:37 PM.
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