2003 - CEL P0136 and P156

[Kstimp]

A couple of weeks after I got my 4Runner, it threw these two codes.
P0136 - Bank 1 Sensor 2 (Passenger, Downstream)
P0156 - Bank 2 Sensor 2 (Driver, Downstream)

I have found TSB EG005-05 that talks about a design change to the O2 sensors. It looks like Toyota recommends part numbers
89465–35710 - Bank 1 Sensor 2
89465–35700 - Bank 2 Sensor 2
a quick google search showed that these are aproximatley $150 each.

From reading this forum it seems that Denso branded sensors are the brand of choice when used in place of the Toyota sensor from the dealership.
The Denso site and the AutoZone site gives: Denso 234-4805 and 234-4804 as the replacement parts. These parts are going for ~$50 each on amazon at the moment

What I can't find though is a cross reference chart showing that these cheaper Denso sensors comply with the TSB.

• Has anybody used these parts with any luck?
• Are these a direct plug-in or are they a universal type plug that has to be wired?
• Did they fix the problem or is this a catalytic converter problem? It seems odd to me that both sensors (or cat converters for that matter) would fail simultaneously.

I have already done a couple of the cheap fixes. ie cleaning the MAF and tightening the gas cap. If there is anything else I can try please let me know.

 

[BOSMECH]

I have used the ones off amazon and they worked just fine.
They are not made by Denso though they are made in America with authorization to use Denso's name so it is hit and miss, I have to do my bank 1 sensor 1 upstream for a 3rd time after it was in for only a year.
But if you are going to do your downstream ones do the mode that others have done using a sparkplug antifouler thing (do a search in the forum here about it) that is what I am going to do next time.

 

[BOSMECH]

found the link to the mod.
http://www.toyota-4runner.org/4th-g...20-yes-i-searched-maybe-i-am-doing-wrong.html

 

[Kstimp]

Update

I replaced the O2 sensors with the above mentioned Denso sensors purchased from Amazon. The CEL didn't immediately go away and still didn't turn off after a ~10mi. test drive. I used an OBD-II scan tool to clear the stored codes. I have now driven about 150 mi. and the codes haven't returned yet. I'll keep this thread updated. It looks like most people who have trouble have their CEL come back on after about a week. Here's hoping that doesn't happen.

EDIT: After driving about 500 mi. CEL came back on. The code is now P0430 (Bank 2 Cat Efficiency Low). I think I'm going to be trying the anti-fouler trick soon. Thanks Bosmech!
Interesting side note, after looking parts when searching for catalytic converters, it seems that the downstream sensors are really upstream of the cat. I believe the system is
exhaust manifold>A/F Sensor (this is S1)>a preheater>O2 sensor (this is S2)> cat

 

[Kstimp]

Catalytic Converter

So just for preparation I was pricing catalytic converters today and magnaflow lists separate parts for a manifold converter and rear converter. link

Any idea which one would need replaced to fix the P0420 code?

 

[TravisT]

So I'm dealing with the same thing on my '04 with about 150k on the clock. I had a P0430 a couple months back. I cleared the code, and hoped it wouldn't come back. It did (but after enough time to get my emissions test completed). I planned to swap driver and passenger side O2's to see if the problem tracked over to a P0420 code. Unfortunately, the wiring harness on one is longer than the other and without extending the wires it couldn't be done.

I ordered a new O2 sensor, replaced it and reset the code again. It stayed gone for longer, then came back, then back off and now back on constant. I haven't thoroughly checked for exhaust leaks, but that is one reported cause. The other is a bad cat.

There are a total of four cats on the 4Runners. The flow is Manifold -> A/F Sensor -> PreCat -> O2 Sensor -> PostCat. The P0430 code is related to the O2 sensor reading after the PreCat. So to answer your question Kstimp, if it was a bad cat, it would be the PreCat on the manifold.

I've heard that it is often a small exhaust leak or crack allowing oxygen into the system, so that may be a much cheaper fix if that is the problem. That's what I'll be checking before I attempt to change the cat.

 

[BOSMECH]

Just did my bank 2 sensor 2 and cleared the codes and a zero point calibration so far so good.

 

[kosan]

I endured the same characteristics. I started by doing the cheap fixes first (gas cap, o2 sensors). Eventually I had to replace both cats. After each fix, I cleared out the codes and they came back after 100-200 miles. Since I have emissions every 2 years, I just dragged out the fixes over a 2 year period.

 

[ricksxfile]

Sensors and CAT issues

Last fall took my 03 4Runner to NoVirg Dealer due to engine check and VSC lights, well, 4 days later and $1800 invoice dealer stated, after replacing 7 sensors the lights once again returned after test drive. No mention of any CAT issues, but dealer stated wanted to replace (1) more sensor and would only charge for sensor, no labor. Agreed and this time I stated, if this doesn't work I'm coming to pick-up my 4Runner. Sensor (8) replaced and dealer test drove and all lights stayed out. Arrived at dealership, invoice was now at $2100, a tad bit miffed after prior comments made (only cost of new sensor). Service agent reduce cost back down $150, plus my $100 discount. Anyway 2 miles from my house the lights returned plus a new one. Called dealer service dept back and informed them of the events, asked if this was experiments or research on sensor behavior or if there was a process where my 4Runner actually gets fixed? Of course, dealer wanted my 4Runner back and stated only 2 more sensors to replace. Stated nope not coming back.

Late May 2015 took 4Runner to get VA state inspection and emissions test to be able to get my new state tags. Passed state inspection and failed emissions test and the inspector stated was a P0430 code and stated this is mostly likely indicates CATs need to be replaced. My dilemma now is whether to take this back to the dealer and do another experiment and research process? Emissions required by end of June or tags penalty adds to my misery.