QITPLEXUS

It is indeed a brand new 100 Amp Alternator. I can not understand why the stock alternator would not be strong enough to handle the circuit - but here is my best theory after further research folks. The problem is defintely in the A/F Heater circuit and my car has the two heated O2 (A/F) Sensors with the relay. Toyota claims (see http://www.autoshop101.com/forms/h37.pdf) that on cold start (which is most pronouncable for the problem I am having) that the two heated O2 (A/F) sensors come on together and as the car warms up (8 amp maximum combined draw), they begin to taper off and on as directed by the mass air flow (MAF) signal to the ECM. The circuit diagrams are in this link as well. This coincides perfectly with how the issue presents itself. The flickering is much stronger in the first few minutes of start up, after which it is somewhat less pronouncable when at idle - yet still annoyingly present. And as the car cools during driving the issue becomes intermittent and even more annoying. My O2 (A/F) sensors are not throwing any codes. It seems there is most likely a poor, yet not completely faulted ground somewhere in the circuit. If I can not definitively determine that a high-resistance path exists in the circuit with my ohm meter, I may in fact need to increase the alternator size as has been suggested in the thread. However, I would prefer to fix the potential high resistivity problem first rather than treating the symptom with a higher output alternator only to potentially run into this again later down the road. I truly appreciate everyone's input. Please add any additional thoughts/insight/expertise. All is very welcome - thank you!

QITPLEXUS

It is indeed a brand new 100 Amp Alternator. I can not understand why the stock alternator would not be strong enough to handle the circuit - but here is my best theory after further research folks. The problem is defintely in the A/F Heater circuit and my car has the two heated O2 (A/F) Sensors with the relay. Toyota claims (see http://www.autoshop101.com/forms/h37.pdf) that on cold start (which is most pronouncable for the problem I am having) that the two heated O2 (A/F) sensors come on together and as the car warms up (8 amp maximum combined draw), they begin to taper off and on as directed by the mass air flow (MAF) signal to the ECM. The circuit diagrams are in this link as well. This coincides perfectly with how the issue presents itself. The flickering is much stronger in the first few minutes of start up, after which it is somewhat less pronouncable when at idle - yet still annoyingly present. And as the car cools during driving the issue becomes intermittent and even more annoying. My O2 (A/F) sensors are not throwing any codes. It seems there is most likely a poor, yet not completely faulted ground somewhere in the circuit. If I can not definitively determine that a high-resistance path exists in the circuit with my ohm meter, I may in fact need to increase the alternator size as has been suggested in the thread. However, I would prefer to fix the potential high resistivity problem first rather than treating the symptom with a higher output alternator only to potentially run into this again later down the road. I truly appreciate everyone's input. Please add any additional thoughts/insight/expertise. All is very welcome - thank you!

01ES300NYC

iTrader: (2)

^^^
did u check your terminals? if you look close you'll see a little rubber/plastic piece where the terminal closes...remove that and tighten your terminal really really tight see if that helps at all....

QITPLEXUS

Great thought! I will thoroughly clean and tighten all of the A/F sensor terminal connection points in the circuit while I am locating the grounds and cleaning them as well. In addition to where they are affixed, I believe the ground points for the A/Fs are via the ECU and the main fuse box.

I'll report back shortly. Thank you!

exxonham

Hey man thats the first I heard about the prob being in the A/F Heater circuit, I am still having the same prob and have even made a thread about it but guess just keep this one open but what I did was a load test on all of the charging system cause I first thought my prob was alternator, I even went through the hassle to take it off to test it at orielys it tested fine and my battery was readying fine at 12v so thought WTF could be prob so ppl told me to do load test to see what all parts of charging system was doing and turns out my battery isent holding all its amps and my battery is the prob cause already did BIG 3. and every thing else checked out. So have you done a load test. Oriellys does it for free dont pay.

and another thing no one else has this prob but when all this happens to me my transmission jumps a little bit, this is with the pulsing lights can anyone explain this

01LEXPL

iTrader: (10)

SO what your all saying is, the new Higher output alternator is not a guaranteed fix?

Ugh, i think i'll just keep ignoring this thing if that's the case.

QITPLEXUS

Folks,

Everything in the main circuit is checking out (battery, alternator, load test, etc. etc.). I have tracked down the issue to the exact point where Club Lexus member DALLISON ended up - that being the A/F circuit. I have a message out to DALLISON to see how if/how DALLISON resolved it, but no word back yet. A/F sensors are NOT O2 sensors. The A/F sensors circuit draws 8 amps when it kicks in at cold startup (if you have the dual A/F sensor circuit with relay) versus 2 amps on a typical O2 circuit. If you have the dual A/F with relay circuit and your pulsing/flickering lights are more prounceable when the engine is cold, I can all but guarantee the problem is high resistance somewhere in the A/F circuit. The trick is finding where. Toyota specifically warns their technicians in their autoshop form (see post #47 above) about it being "critical that all connections in this circuit fit properly and have no resistance" since the current draw is so high. Club Lexus member O1ES300NYC suggested checking all the terminal connectors which is an excellent idea (see post #48 above). I will be trying that once I can get back under the hood in the next day or so. Hope this helps.

yeskay

A/F sensors are common only in strict emission states like CA.

QITPLEXUS

That's interesting. This car was purchased and put into service in the state of MD. Is MD a strict emissions state?

pauloil

I have read this topic and was glad to see some talk about load testing believing he is talking about voltage drop testing. voltage drop testing should be the first test in all charging systems evaluations. here it is explained:
http://www.aa1car.com/library/voltage_drop_testing.htm
anyway, the simple alt. testing at the car parts store will not fully test the alt's regulator. that is what I think is wrong here. prolly doesn't matter if you upgrade to a stronger alt. if the cables are good. what that means is the voltage drop is less than 0.2V under load(say at 2K rpm with window defrost, fan on high and headlights on) across the connector at the batt., on ground cables, and the cables running from alt. to batt. On my cars, bad cables have ruined an alt. and it wasn't until I replaced starter to pos. batt. cable that the 3rd alt would fully charge to 12.6V. in an oldsmobile, the lights were wobbling a lot until I stuck a new volt. regulator in(new alt.)

QITPLEXUS

The Final word on this folks .. after many weeks of exasperating effort.. is that the problem is a known one (quoted directly from Lexus Corporate offices in Torrance, CA). It is in fact in the A/F circuit. There is no official bulletin (TSB) or recall. Our 2000 RX300 was at the dealership for two weeks straight. The shop foreman took it home and drove it at night to dig in further. It was fully checked on all Lexus equipment in the most comprehensive fashion imaginable. A brand new lexus battery and alternator were added/replaced multiple times. All grounds were thoroughly tested - and an additional one was added to no effect. Voltage tests, drop tests, .. every electrical test was performed leading to this conclusion. I received practically hourly updates as the tests were occuring. On the last day, another 2000 RX300 rolled into the shop with another issue and it was flickering exactly as ours was. I am awaiting a call from the Lexus Technical Staff in Torrance this coming week and will post another update as soon as I do. We are demanding an explanation for this. The fact that is a known problem and there is no fix for it is not an acceptable outcome for a car of this level of quality.

01ES300NYC

iTrader: (2)

good luck .... keep us posted!

OceanView

The question is what do you think Lexus will do after all these years?
I have the same problem by the way.

Good luck and please keep us posted.

QITPLEXUS

While we understand it is out of warranty, since the problem is very widespread and known to Lexus Corporate, we believe Lexus at a minimum can and should be willing to fix their automobile at a price. This would be an acceptable outcome to us at this point. Sorry to hear you are experiencing same. To confirm, the problem goes away when you temporarily remove your A/F relay or fuse? That's the sure-fire way to determine if this is the issue. I haven't seen user DALLISON on in a while, but am curious if he/she ever was able to resolve it. Unfortunately we can't run arround without heating these sensors as it will eventually result in an improper air/fuel ratio, throw a code, and potentially cause other problems. Ironically the car runs a bit smoother with the heaters disabled due to the lack of drag on the alternator.

QITPLEXUS

Folks - as this progresses, I am sorry to say that I would strongly not recommend anyone purchase another Lexus vehicle until further notice based on the experience we have been through with Lexus Customer Service. The bottom line is that the Lexus dealership representatives including the shop foreman fully recognize there is a problem with the A/F circuit. Lexus Customer Service responded to this by sending their Field Representative to the dealership. I was told by Lexus Customer Service that the Field Representative told everyone at the dealership that the problem is "normal" and that "there is no repair for it." As such, Lexus is admitting they have a problem with no fix, they are sending people out to tell their own people that their own trained technicians (and the entire service side of the dealership for that matter) are wrong and that there is no problem, and having Customer Service tell me (the customer) that one technician "trumps" another - and I quote this as just being told to me by Lexus Customer Service today. The dealership clearly does not concur with Lexus Corporate. We are in the process of gaining legal counsel and representation as we are concerned about the aspect of this circuit causing a fire and the car was purchased for our young daughter to drive. When I shared this with Lexus Customer Service, they assured me that the "problem" would not cause a fire. How can they make such assurances if they are first denying there is a problem while at the same time stating that they do not know what the problem is, and truly do not know how to fix it? All this while the problem has all the properties of a shorting or short circuit that can surely lead to a fire? The car has been in the shop now for 21 of the last 30 days. I promise to keep everyone closely informed with future developments as they occur.