Jacklalane

My rx300 AWD (maybe all of them are AWD) with 269000 miles and is a fairly recent addition to my garage, has started bogging down when I accelerate. It feels similar to a carbureted system that is flooding out...That is, it stumbles when I step on it, and as I back off it accelerates briskly until the rpms reach approximately what they should be according to my pedal position. Also it doesn't seem to shift at the normal times and my O/D has simultaneously begun working somewhat intermittently. It works most of the time, but even then it seems to shift in later than it did previously. I noticed that if I am going somewhere and it is in the mode of not going into O/D (maybe a Lexus version of limp-home mode), once I reach my destination, shut it off and start again I will have overdrive again for a while.
The check engine light is also on and I took it to AutoZone to have the codes read and it pulled up codes: 0325, 0330, 1135 & 1155. Also my VCT light is on...I'm not even sure what that means (whether I have a switch pushed that I shouldn't etc). My intention at this point is to change out the knock sensors and harness first as that looks like the most challenging job, but also one I think I can handle w/o taking it to my tech. Then to change out the upstream fuel/air sensors with new Densos which looks pretty straight away to me. Are there any other preliminary tests that you might suggest (I saw where someone had resolved one of these codes by replacing one of the fuses in the box on the drivers side under the hood, but can't seem to find the post again at this time ). BTW, I was on a thread where the issue/question of Bank1/Bank2 kept coming up with contributors wondering why it would be designated that way (with B2 being on the front of the engine). I might suggest that is was done that way because cylinder #1 is toward the rear of the vehicle and #2 is toward the front. I could see where they would be designated that way on RWD vehicles where the engine is oriented 90° from the position on the AWD/FWD vehicles and for the sake of consistency just kept the designation that way...Just a thought as the thread never did seem to come to a resolution of the cyl 1 cyl 2 question. Please let me know if there might be a better place to post this so as to be in an appropriate place as well as more eyeballs. BTW, this is one awesome site as I belong to several forums (Nissan, Cadillac and Silverado to name a few) and this one ROCKS hands down! Thanks in advance for any guidance you might be able to offer.

fastnoypi

IMO, i'd troubleshoot the knock sensors as the last possible cause for CEL lights. They typically last the life of the car. Both your bank 1 and 2 O2 sensors may not be providing the correct input to your ecu which in turn knock will result.

How much do you know of the service history? When were the plugs last changed?
If you can unplug the o2 sensors, you can check if they are in spec with a multimeter before replacement.
To confirm this is a repeatable problem for you, reset your ecu by disconnecting/connecting your battery and see if the codes will come back.

The simplest thing i would try at first is to clean the MAF, for a correct a/f mixture the maf and o2 sensors work in tandem. Should one or both have trouble, the mixture will not be optimal and the ECU will resort to failsafe maps.

Jacklalane

Thank you for your response. The previous owners were unable to provide any maintenance records. Can you provide a link to the test points and procedure for checking the O2 sensors? IE, is it a simple open circuit/closed circuit (OL or 0.00) reading between the connector points or is there an ohm range through the device that is considered normal?
I just got off work and have to be back there in a little over seven hours, but I will disconnect the battery before I lay down and hook it back up before I go to work.
What is the MAF and how do I clean it? If it refers to the air filter, it is new.
This acceleration/shifting/OD condition seemed to occur simultaneously. Is there any conclusion that might be inferred from that?
The timing belt has not been changed since 153K miles. My tech is going to change that and my water pump and thermostat the week after next. I am wondering if my belt is stretched and is throwing off my valve timing. Could that have anything to do with these issues?
Should I drive something else to work until this is resolved?

Kind Regards,
Russ (Jacklalanne)

Jacklalane

Also can you tell me anything about the VSC (I said VCT in my previous post...sorry) light being on?

salimshah

Welcome to CL

Please read through the sticky threads. There are DIY links as well.

We have covered the orientation and designation of banks as well as cylinders in the sticky.

If you plan to change the harness for the knock sensors, I would say it is a bad idea. Once you there you might as well replace the knock sensors (based on your milage and the effort/expense involved in tear up and rebuild).

Salim

fastnoypi

the maf sensor is located between your throttlebody and your airbox https://www.clublexus.com/forums/att....-05-09.03.jpg

regarding the o2 sensors...here is troubleshooting from the FSM

DTC P1135 OR P1155: AIR/FUEL SENSOR HEATER CIRCUIT
MALFUNCTION
CAUTION: If ECM replacement is instructed in following testing, always
ensure ECM connectors and ground circuit are okay. If either
are suspect, repair and repeat testing to confirm ECM
malfunction. If ECM is replaced, ECM must be programmed with
proper ignition key code for engine immobilizer system. For
programming procedures, see COMPUTER RELEARN PROCEDURES
article in GENERAL INFORMATION.
NOTE: Bank No. 1 refers to bank which includes cylinder No. 1. Bank
No. 2 refers to bank without cylinder No. 1.
Circuit Description
Air/Fuel (A/F) sensor monitors exhaust gas oxygen content and
delivers an input signal to ECM. ECM uses input signal to control
air/fuel ratio. A/F sensor includes a heater. DTC P1135 is for bank
No. 1 A/F sensor. DTC P1155 is for bank No. 2 A/F sensor. DTC is set
when A/F sensor heater output is more than 8 amps or when heater
output is less than .25 amps. Possible causes are:
* Open or short in A/F sensor circuit.
* Faulty A/F sensor heater.
* Faulty ECM.
Diagnostic Aids
Using scan tool, read freeze frame data. Freeze frame records
engine conditions when malfunction is detected.
Diagnosis & Repair
1) Access ECM behind glove box. Turn ignition on. Using DVOM,
backprobe at ECM harness connector and measure voltage between ground
and terminals No. 3 (Blue wire) and No. 4 (Green wire) at ECM harness
connector E6. See Fig. 2. If both voltages are 9-14 volts, replace
ECM. If either voltage is not 9-14 volts, go to next step.
2) Disconnect suspect A/F sensor harness connector. One A/F
sensor is located in each exhaust manifold. Measure resistance between
terminal B+ (Black/Red wire) and HT (Black/White wire on bank No. 1 or
Black/Red wire on bank No. 2) at A/F sensor connector (component
side). Resistance should be .8-1.4 ohms at 68 �� F (20 �� C) and 1.8-3.2
ohms at 1472 �� F (800 �� C). If resistances are not as specified, replace
appropriate A/F sensor. If resistances are as specified, go to next
step.
3) Check for open or short in wiring between EFI main relay,
A/F sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS
article. Repair as necessary.


Google for : lexus rx300 manual pdf ... it will come handy in the future.

fastnoypi

one other thing to also consider in your troubleshooting that occasionally contributes to knock is VVT.
Due to infrequent oil changes, the screens of the VVT solenoids can get clogged. Do a search on the forum to locate them and check/clean the screens.

Jacklalane

My original post states:
"My intention at this point is to change out the 'knock sensors' and harness"

So, do you think that I might reasonably conclude the harness is bad since both sensors are showing up? The reason I mentioned it is with the vehicle having almost 270/K miles on it and the harness being exposed to engine heat for that long...and being that deep in the block if it did go bad later time, for $30 for an original Toyota replacement now it just seemed lo be the reasonable thing to do.
This may be a dumb question, but since the air /fuel sensors are a bit more spendy to purchase (and also not bad to get tp and remove) is there a way to clean or otherwise breathe some more life in them when they are coming up in the codes?

Also, can bad knock sensors have anything to do with the overdrive issue?

Regards,
Russ (Jacklalanne)

Jacklalane

Hi Fastnoypl,
I didn't see your post until after I had posted mine.
Thanks for all the information to absorb.
Do I read your post correctly, that I am being premature in planning to replace the knock sensors and harness and air fuel sensors without some more preliminary troubleshooting?

Jacklalane

I don't want to do any unnecessary work, I was just thinking that with the codes pulled and the heat produced at those locations it seemed reasonable after so many miles it might be a likely course of action.

fastnoypi

Yes, I believe you are being premature to be replacing things. I'd prefer to deductively troubleshoot first before throwing money at a problem.

Jacklalane

I'm picking up what you're laying down. Thanks...Would you mind suggesting an order of operations if you were experiencing the same symptoms on the same vehicle (miles wise) and assuming no previous component replacements? (The only one I know for sure is the timing belt at 153K) Would you start with a particular process you have already given me in one of your posts? Is there a specific test for the knock sensor component w/out digging deep?
Don't mean to ask another dumb question, but I'm shaky on the nomenclature used in some of the shorthand used to denote component acronyms. What is the "VVT"?
Which of these components, if either, is most likely to lead to my intermittent overdrive issue?
Thanks for your time, patience and willingness to share your knowledge. It is greatly appreciated.
Regards,
Russ

fastnoypi

VVT refers to the variable valve timing system for intake cam advancement. The VVT solenoids are also called OCV..oil control valves which actuate based on oil pressure. If you search the forum for keywords VVT or OCV DIY, there should be links and pictures of their location so you can remove and clean the screens.

Forget about the knock sensors already. There is no practical way to test them unless you have an oscilloscope and smack your engine block with a hammer to verify the readout.

Your overdrive issue may or may not be related. Troubleshoot one issue at a time.

Jacklalane

Got it...Thanks

Jacklalane

Could anyone recommend an adequate scan tool for the DIYer that I won't need to make payments on? Thanks in advance...