nah2323

Hey everyone,

Just checking to see if my situation will prevent a proper fix of the P0171 CEL.

I recently had a bad TPS, and replaced it with an OEM one (stealer). The delaer said that a bad TPS fried both of my cats. And trust me, fried cats isn't good like it would be in cheap chinese food. I said HOGWASH, replaced the TPS, and put the URD sim in there. The true test would be to sniff the car to see if the cats are actually bad, and replace the secondary O2 if the cats are good, but I needed and inspection at the time, and did the fastest cheapest way to get me a new sticker. Only because the damn state has the new cameras that read your plate number and inform the cop of any registration hiccups. Don'tcha love NY? Now, I'm getting around to fixing it legitimately.

So my question is, since I have the URD sim installed for the SecO2, does it over correct the signal to the ecu and mess with the fuel trim, enough to make the PrO2 fault provided the rest of the sensors are proper?

Thanks in Advance!
nah2323

nah2323

I currently have an OEM Denso 89467-35011 sensor in front of my cats, and am looking for an aftermarket "Non Bosch" number for a new sensor. In the searches, it looks like its an A/F sensor, not a typical o2 specifically.

Has anyone ordered a Denso 234-4162 in place of this? do I have the correct info here?

nah2323

************** UPDATE **************

I threw the Actron on the OBD-II interface and had three codes.

P0136
P0171 - Pending
P0136 - Pending

From what I gather, the P0136 should be taken care of by the URD Sim. Why am I getting that code?

mt_goat

No. It only effects the signal from the rear sensor. The rear sensor has nothing to do with fuel trims, all that is from the front sensor. The URD sim will only stop a P0420 code.

mt_goat

The front sensor is very year/model specific. Best source of info on it is the URD site: http://www.urdusa.com/index.php?cPat...pp2r92eeln2uu4

mt_goat

That would be a natural assumption since they call it a rear O2 sensor simulator, but the name is a little misleading and your assumption is wrong. The URD sim does require a fully functional rear O2 sensor to work (as stated in the URD info). When working it only stops a P0420 code.

nah2323

I know that it only simulates or corrects the signal from the O2, and that it doesn't replace the O2 entirely. It's only connected to 1 ecu wire, so it couldn't correct the heater circuit. Unless it's magic..

mt_goat

You're welcome

nah2323

thanks for the input Goat

I guess what is still out there is this..

With a new TPS and MAF installed within the last 3 months on separate occasions, what could possibly be causing the P0136, and the P0171 codes? Is it likely that both of the O2's are bad? Or, could it potentially be a fuel problem? The fuel filter was changed since I've owned it. (within six years, but more than likely change within 4).

TheDurk

The P0136 is specifically linked to the rear 02 sensor heater circuit--either bad sensor, wrong sensor, bad connection at plug, bad wiring harness, and/or, in your case, something that got screwed up when the URD simulator went in. When, exactly, in the sequence of all you did, was the P0136 first displayed? I know you said you had a new rear sensor--exactly what sensor did you put in and when? oh, and exactly what truck do you have? Year, 2/4WD, auto/5sp, Cali/49 (Cali--I assume, since 2 cats), and engine. (Put all this in your sig and you will get more/better help.) Have you done a resistance check on the rear o2 sensor heater? If not, this last needs to be done now.

In my opinion, idea here would be solve the specific P0136 first. However, the rear o2 is not normally a cause for a P171, so they probably won't go away together (absent a crossed wire or such due to the sim).

Finally, there is no way the Denso 234-4162 goes in the front of a 2-cat system. It is a 'normal' o2 sensor, and you need an A/F sensor. Go to URD as MG suggested.

nah2323

the P0136 just showed up for the first time yesterday. The URD simulator was installed months ago. The installation is perfect, as I'm a licensed master electrician (it's what I do for a living.)

The rear sensor is original from when I bought it, about 6 years / 60kmi ago (I think. something about 5 years ago the dealer replaced that had something to do with A/F bank 1. I'll dig through the glovebox and try to find that invoice.)

I'll drop my RDMM on the heater circuit to check resistance. What is the nominal value of a sensor "within spec?" I downloaded the FSM from club lexus or something, but its a horrible layout. Maybe I'm not using it correctly. Is there a link to one that is just a solid PDF without the hyperlinks?

After further research, I found out that the 234-4162 isn't thecorrect sensor for my application. The URD site was helpful and gave me the correct sensor which I found on amazon for $122.xx

Thanks for the help. I may actually try heating the front sensor to check the switching. my RDMM records and graphs anything I want it to, so in essence, i could leave the sensor in the pipe, and run the car to check the switching rate. Here's a sample of the RDMM graphing.

mt_goat

X2! Some of the earlier FSM were easier to use but we don't know what year/model/engine you have.

nah2323

updated the signature.

mt_goat

Well the 4runners online FSM are less common, I did find a 2000 Tacoma FSM with 5VZFE info which may be the same: http://www.ncttora.com/fsm/2000/index.html


The O2 sensor testing part: http://www.ncttora.com/fsm/2000/Repa...ensor/insp.pdf

mt_goat

Looking at my 2001 Tacoma FSM it shows the P0136 trouble areas as:

*Open or short in rear O2 sensor circuit
*Rear O2 sensor

There is a different code for a problem with the heater circuit of the rear sensor, a (P0141). So that link above may not help, unless you can get the hyperlinks to work or find the diagnostic page (DIxxx) it references. I know those online versions suck. They reference section/page numbers but with no index of section/page numbers. And the hyperlinks never work for me. I'll stick with my hard copy FSM.

In my 2001 FSM the P0136 is thrown when the voltage output of the rear sensor remains at .45 V or less to .60 v or more when the vehicle is driven at 31 mph or more after the engine is warmed up. (2 trip detection logic)

mt_goat

Found some of the links in that online manual:

P0136:
http://www.ncttora.com/fsm/2000/Repa...on/cip0136.pdf

P0171:
http://www.ncttora.com/fsm/2000/Repa...n/cip0171p.pdf

TheDurk

Sorry, read my FSM a little too fast. So instead of heater resistance you need to look at the rear sensor output curve. Can your Fluke do that? I have a BR-3 and a laptop for that purpose.

Seems pretty likely a bum sensor, unless a zero points to a possible bum connection/wire harness. 60k/6 years is fast for a rear sensor. Could its premature death be related to the TPS event that killed the cats? I don't know, but it seems possible if the TPS thing was after the sensor change and coincident with the P0136 showing up.

The A/F designation refers only to the front sensor in the 2-cat systems. Bank 1 is all we have, no Bank 2 on a single exhaust system. Bank 1 Sensor 1 = Front (A/F) sensor. Bank 1 Sensor 2 = Rear (O2) sensor. So maybe rear sensor is older? In either case (old or killed by fuel), it then seems possible that both sensors require replacement to clear both codes, since in theory one has nothing to do with the other, unless they were both killed by the TPS event. My approach has been to look to sensor first if sensor is old 80k+, and look elsewhere first if newer than that.

Oh--I did not mean to insult your wiring skills. I was merely being analytical, that's what I do for a living.