century29

Hello all. I'm new to this forum and have searched it extensively in the last few days regarding my codes.

I have a 2002 ES300, 180k mi., and recently began to experience engine stuttering while accelerating and more extreme stuttering while at cruising speed only applying light throttle.

I checked codes and got
P0051,
P0102,
P0113,
P0171,
P0300,
P0301, and
P2238

Based on what i've found on this site regarding these codes, here is what i have done so far:

Replaced (and properly gapped) all spark plugs with denso iridium,
Replaced all 3 Bank 1 ignition coils (denso)
Replaced air intake gasket
Replaced vacuum switching valve (found cracked)
Replaced PCV
Replaced various questionable vaccuum hoses
Cleaned MAF sensor
Cleaned throttle body
Inspected throttle body hoses for cracks/leaks

Problem still exists.

My next step I think is to replace the Oxygen sensor. Since P0171 denotes bank 1, would this be considered the "downstream rear" O2 sensor? Denso PN (234-4064)?

I'm a little confused with the front and rear, as well as the upstream and downstream, so i just want to make sure i'm buying the right part and replacing the right sensor. I'm a week into this and I'm getting frustrated.

If the O2 sensor doesn't fix it, all i can think of left to do is replace the MAF. Does anyone have any other advice?

Thanks in advance!!

ES300NZ

"Cleaned MAF sensor" <- that can be the cause of problems like this. Both the cleaning of, and the actual sensor itself. I damaged a sensor once with MAF cleaning solution, and it caused me no end of trouble trying to work out the actual problem since I didn't guess it was that ... for a while ... (read $500 in parts and several months of pain).

The mal functioning maf sensor caused the engine to run lean, which cooked the o2, which I also had to replace.

It sounds like you've noticed alot of age related issues and tackled those, some of which would have no relationship to the symptoms you've described. I like that method of fix it all now, and never worry / move on. Well done.

I would replace the A/F sensor's and the o2's (all of them before the cat's. my guess is those are the actual problem from all the codes I read there.

I would also check that the alternator was putting out the right voltage, and if you know how, I would test the voltages at the sensors on the power (switched/ign) wires to see why those voltage errors are coming up. But again, thats me, I can read the diagrams and work that out, for you I'd just assume it was those four sensors and go from there.

Then, I would find a cheap, but functioning second hand MAF to prove out the issue. If I liked the car I would get a new one once proven. In fact, you could do that will all the sensors actually. Just remember to fit, test, then fit test, until you work out that actual fault. Fit them all, solve the problem for sure, but never knew the cause .. nah, that's not my style.

EPayne42

Symptoms sound like VVTi's (Oil Control Valves), but check out this video. I like the carb cleaner test for finding leaks.

EPayne42

I'm betting toward a lean condition. How old is your fuel filter? Do you have a fuel pressure gauge?

I like EZ300's advice to check the charging system too.

tomf

My guesstimate is that you have a bad maf or bad a/f sensor. It would be the upstream bank 1 sensor 1. The one between the firewall and the engine. I would replace the A/F sensor first because its been my experience that is the most likely cause. They tend to go bad at about 130K miles give or take. I see your car is at 180K. You'll need to replace it sooner or later.

If the replacing the A/F sensor does not fix it, replace the MAF.

century29

Thanks for the responses!

As far as the voltage goes, i replaced the alternator a few months back. I don't know if its a left over code that i just didn't clear out, or maybe the new alternator is doing something funky. I'll test it.

So here is where I'm still confused. below are the listed O2 sensors for the car from rockauto...

A) DENSO Part # 2344064
Downstream Rear; DENSO is the O.E. Manufacturer / Oxygen Sensor

B) DENSO Part # 2344261
Downstream Front; DENSO is the O.E. Manufacturer / Oxygen Sensor

C) DENSO Part # 2349043
Front Right

D) DENSO Part # 2349047
Upstream Rear; DENSO is the OE Manufacturer Air Fuel Ratio Sensor

E) DENSO Part # 2349042
Upstream Front; DENSO is the OE Manufacturer Air Fuel Ratio Sensor

I thought that the non-california emissions cars used O2 sensors and the California emissions cars instead used A/F sensors. I believe A and B are for non-california emissions cars. And C,D and E are for california emisions cars. Is this correct?

If so, there isn't an O2 sensor listed as upstream for my car. would I use A, the downstream rear? Or do non-california cars also use A/F sensors in the upstream location?

My car is not a california car. Sorry for my denseness on which O2 sensors!

PFB

You should also check the large snorkel hose(s) behind the MAF, for cracks. They are notorious for cracking, and allowing unmetered air to bypass the MAF.

It's best to take them out and examine them carefully.

Phil

century29

Thanks PFB. I did look over the large snorkel hose behind the MAF and the one in front of the throttle body. All look good. thanks.

Anyone have any clarification which denso part number I need for replacement of my bank 1 O2 sensor?

ES300NZ

thats damn good advice actually.

tomf

Go here http://densoautoparts.com/find-my-pa...icle-selection to determine which sensor you need.

According to Denso, the one you need is labeled by Denso as "Upstream rear." Part number 234-9047.

Denso does not list DENSO Part # 2349043 as applicable to your model year car. Don't know if you can use it or not. Update: Amazon lists 234-9043 as an old model of 234-9042.

The two upstream sensors are A/F sensors. The two downstream sensors are O2

FYI there is no such thing as "upstream rear". It should read "upstream right." I think Denso labeled it such because people were getting confused by the proper description. Left and right refer to a side of the engine. The engine is turned 90 degrees in the engine bay. So the front of the engine is towards the passenger side. The right side of the engine is closest to the rear of the car, etc. Bank one is on the right side of the engine, which is also closest to the rear of the car. Bank two is one the left side of the engine which is closest to the front of the car.

In this case when Desnso says front, they mean left. When they say rear, they mean right.

On your year ES300 I don't believe there is any difference between the Cal and non-Cal engines with respect to these sensors. All the upstream sensors on as 2002 ES300s are A/F and the downstream are O2.

century29

Thanks Tom. Exactly the info i was hoping to find here. This site is a great resource.

The part is on order and i'll update the thread with my results. It drives me crazy when people put up troubleshooting threads on forums and then leave you hanging for the outcome.

century29

Fixed!

The Air Fuel Ratio Sensor was what ended up being the culprit. After replacing it, all symptoms immediately disappeared and so far, the CEL light has not come back.

thank you to everyone who helped me troubleshoot this.

You can see the difference between the new one and the old one. Lots of carbon build up on the old one.

ES300NZ

The carbon build up just tells you that the engine was running quite rich

JJC21

Thank you very much tom, your immaculate description made it very easy to understand the difference between the sensors and which one to change. No more CEL. Anyone inquiring about p2238 should look at tom's reply, it will save you a lot of money! Thanks again

Mphidd

I have a stupid question. Can someone tell me if the air fuel ratio sensor is the same thing as an oxygen sensor? I'm having the same kind of issues with my 1999 Lexus ES 300 and just trying to figure out which parts I need to replace before I start buying parts at random