Code 41

[93ls400walt]

I've been having a code 41 issue. I checked my code after my Ls started to stumble under an A/C load with more than a slight attempt to accelerate. Same thing on going up a slight incline. After new coils, Already has new wires,caps, rotors and plugs. There was an improvement, but still there. I replaced the under car and in the gas tank filters. I actually gained a couple of hundred RPM reading on a cold start. To 1,100 rpm. And around 50 rpm when warm. After the in tank filter change. I think it was slightly clogged. Pulling the fuel pump assem. out. The filter did not drain untill I turned it sideways. Assuming the bottom of the filter was clogged. Also throttle body cleaned twice. Many Seafoams done. And most recent BG44K.

I did replace the TPS. And did many ohm meter adjustments/readjustments. I feel it is right on the specs. But the code 41 always comes back. I know that the wire harness and or ECM can be at fault. But if anyone has any advice. Please respond.

Also, I have read that if a code 41 is present. The ECM goes to a fault mode. With the timming fixed a 5 degrees BTC. Do you think that this would cause the engine to stumble with a 1000-1500 drop in rpm? The rpm will not increase untill I let off the gas then press down slowly. Also there is " PUFF " sound that occurs when the engine rpm first drops. Not through the exhaust. From under the hood.

Thank you, Walt

[LScott400]

I would suggest pulling the ECM to inspect for leaking capacitors. (But then you knew I would, huh?) :)

[cruzzin02LS]

Walt,

I too have/had a 93 LS400. After replacing both O2 Sensors, and both Catalytic converters (all aftermarket), the EGR pipe (that goes from the passenger side exhaust just before the catalytic converter, to the intake manifold - a real Bxxxx to get to since it is like an inch from the firewall) and of corse forward and aft catalytic converter exhaust gaskets, I finally solved my problem. I had a slight crack in the EGR pipe which actually introduced an additional amount of oxygen into the exhaiust stream confusing the ECM that the engine (right bank only) was operating too rich and tried to lean out the mixture to compensate. So the stumble and lack of power became apparent due to the lean mixture. I had awesome mileage 23mpg from a 13 year old car! Well this eventually took its toll on that one catalytic converter which rendered it nonfunctional and destroyed the o2 sensor as well. The only reason I replaced all 4 O2 sensors and both catalytic converts is becasue I was able to buy all four sensors plus the installation tools cheaper than 1 Lexus sensor. About $180 for the universal sensors which require you to splice them into the existing harness. As far as the Cats are concerned, I replaced only one at first, but is was slightly different from the Lexus converter. It appears after replacing the other (CATCO OEM Direct replacement) the exhaust stream evened out, now both the left bank and the right bank (cylinders) are now working better than I ever had it since owning my car after its purchase with 67k miles. It now has 130k and still going strong. My son made me an offer I couldn't refuse, so now I drive and own a 2002 LS430. *BLEEP* you think any generation LS400 is nice, drive an LS430 - what a refined, maticulas and near perfect machine. Sorry MB and BMW you don't have a candle you can hold to a Lexus - keep trying.

[93ls400walt]

Very interesting!

First off, thank you for your reply. How did you fiqure this out? Did you have any other codes along with the 41? Or noise in the engine compartment?

Thank you, Walt

PS, I also am planning on pulling the ECM as LScott400 suggests. And inspecting for leaking caps. I may send it off to an ECM repair shop either way. Obvious leaks or not.

[cruzzin02LS]

Walt,

I took my car to the Lexus dealer because I was sick and tired of replacing parts that had no effect of what I wanted fixed first and has just started going into the fault mode as well as an engine check light! Well after several hours of other work and engine check light diagnostics, they told me their were several default codes stored where every they are stored (I do not remember the codes), and told me that the starting point or the code that took priority was the passenger side forward O2 sensor. They explained even after replacing the sensor (estimated $250 including labor) that this was a starting point and no guaruntee that this will fix my driveability issues and lack of power not to mention severe pinging ( I use nothing but 93 octane - plugs, wires, caps, rotors, coils, all new and all Lexus parts). So when I changed all the O2 sensors the car drove better since it no longer went into the fault driving mode, engine check light stayed off, but the driveability issues still existed. I remember reading somewhere that if an O2 sensor goes bad, the mixture will go rich, and a rich mixture reuins catalytic converters or maybe it was too much oxygen and causes the cat to over heat and break down - what ever. So I change the passnger side cat and it seem to change everything more towards the better. Since the two cats where no identicle I then change the other cat and now, well the car is back to being the sweet LS that it was meant to be.

First thing is first - why did the cat fail? Bad O2 sensor. Why did the O2 sensor fail? Too much oxygen being drawn in through a craked EGR pipe. Why did the EGR Pipe go bad? Design flaw and age. They all seem to crack at about 10 years in the same places - the area of the pipe that is conveluted to allow for bending the pipe into place if need be. They will start small and you will not hear the slight exhaust leak for a few months, until is get big enough and even then it doesn't get very loud - it's a Lexus! But this small crack seems to be enough to introduce atmosheric oxygen into the exhaust stream which appears to be enough to confuse the ECM when computing Air fuel mixture under load. I feel it keeps the mixture too lean, causing a lack of power, a stumble when first depressig the accelerater pedal, and excessive pinging when under heavy acceleration and shift change which is the way I drove my LS.

EGR Pipe - Lexus $132.00 (I installed this pipe myself it at the same time I replaced my started and the two knock sensors (these siensors didn;t need replacing just wanted to replace them because of the age and they were right there and easy to get too)

EGR Gaskets - Lexus $18.00 est.

O2 Sensors Forward - Walker Aftermarket Univeral - splice in type

O2 Sensor Aft - Walker Aftermarket Universal - splice in type

O2 Senor Tool Kit - ? I don't remember but it made removal and installation a 15 minute job for each side, including the time it took to jack the car up, remove the wheels and put on jack stands!

Catco Catalytic Converter - R&L - $276.22

http://www.overnightautoparts.com/catalyti...2&brand=916 They come with gaskets but go to Lexus and buy the real ones. They are thicker and higher quality - albite $12.00 - $15.00 each

I am now dealing with front suspension issues!

[VBdenny]

I heard you almost have to remove the transmission to change the EGR pipe. What is your take?

[93ls400walt]

Thank you again. And for the fast reply. I will take a close look at the EGR pipe. And try to fiquire out how to retreive stored codes.

Walt

[cruzzin02LS]

No Sir! I went out and bought a 3/8 inch drive metric set of crows feet sockets (used upsidedown) to get to the awkward to get to nuts or bults above the cats and those that hold the EGR pipe to the exhaust system. This method also allowed the bolts and nuts to be torqed to spec when tightening. Bear in mind I did this to change my starter which required the entire top of the engine to be removed, which made it easier to get the the nuts that hold the EGR pipe to the intake manifold. Oh yea there is only an inch or so of space before hitting the fire wall so it was like a 4 degree at a time rotation - took forever - but i did it and no more leaks of any kind and its almost as quiete as it was when new 13 years ago!