CLFORTNER

Last may 2012 i had knock sensor codes 0330 0325 0171. I had the knock sensors replaced, both. I drove the car the day after getting out of the shop. Guess what? Knock sensor codes again. Back to shop. Replaced wiring harness they were asked to replace the first time but didnt. Got car back, drove ok then 3 months later, knock sensor code again. This has progressed over past year to the point that i am getting the code every time i drive the truck more than 1 mile. Place that replaced sensors said they updated their computer last july and doesnt have record i had truck repaired there. They will replace knock sensors and harness for $1000. Im sure they will. My question is this, should i have to be replacing both the knock sensors and harness again in one year. Im very frustrated with this, and cant afford to keep throwing money at this car. I am currently unemployed with bad heart condition. It has 189999 miles. Otherwise it has new maf, new timing belt, new water pump, new knock sensors, new wiring harness, new transmission pan and gaskets new battery, all in past 12 months...any ideas are greatly appreciated at this point...help!!!!!

salimshah

We're eom parts used?

A good shop or dealer can use a oscilloscope to see the electronic signal and confirm or trace the problem.

salim

kosogo

I has as mentioned earlier bought the car with Knock sensor alarms...and I run 1 full tank with 98 octane Gasoline, and guess what - the alarm is gone!!: The recommendation to fill one or two tank of 98 gasoline i got from a friend that has worked as a mechanic for years and years, and he does that once a year with every car he owns. My RX300 did not like the 98 octane, The alarm came on almost every time, but I reset it at every chance, and when i went back to regular (95) fuel, the alarm showed up more and more seldom and now it is completely gone. if it comes back on i will thy the same again....

However, I will change the Knock sensors anyway since i have bought them and need to do some engine work anyway (in due time to change cam belt).

Anyway.
My theory regarding knock sensors:
(Knock sensors are probably accelerometers, of some type, that wil register a knock in the engine (just as if you hit it with a hammer) due to unregularities in the ignition.
If it is not the sensors that have failed (and surely if new sensors are installed, they will not fail both of them after just a few weeks) there must be something else. Most probably in my case, the engine misfired due to carbon deposits in the combustion chambers. These carbon deposits will start to glow and cause the gasolin/air mix to ingnite before it is ignited by the spark plug...and then the knock sensor wil register it as a knock. so the cure will be to remove these deposits either machanically by overhauling the engine head/top times 2, OR remove it by a engine cleaner additive in the gasoline, OR, as i did, with one tank of higher (98) octane gas.
One other thing is with a lot of time with the car on idle, low revs and short distances with a lot of start and stop, i guess you will get carbon build up, and the cure is to take it for a long drive, let it get warm and push it a little bit once in a while...

one other thing that can cause the engine to knock is damaged bearings in the drive shaft or at the king bolt in the pistons rods. If you listen to the engine with a solid metal rod (one end on the engine block and one end to the ear) you should be able to hear clear knoking or slamming - you will not misunderstand if you hear it...

Anyway, that is my thinking for today, Good luck and please post experiences...

Cooldaddy

I'm am very interested in the last post kinda makes sense I believe I will try it. Some racing gas and see if it works ill keep you posted may ride out tonight to try it I am having the sensor code and no OD. I'm interested to find out if it doesn't work. Ill just change with all Orem parts and do myself.

salimshah

There is wish based diagnosis and there is the reality. Possibilities are ..

1. There is engine knock due to pre-ignition ... You can list all possible reasons .... low-octane gas/carbon-buildup etc.

2. The knock-sensors (+ wiring harness) has gone bad.

3. Combination of 1 & 2

IMHO as the sensors age and deteriorate, they produce failure signature for acceptable conditions. In my case the problem got worse with time (see my notes in the DIY section) and got to a point where I was driving with the OBDII connected to reset CEL and recover the over-drive.

Proof for me: After I changed the knock-sensor, the CEL has not come back on and no other changes were done.

My speculation is that the sensors are acoustic devices with a resonating chamber tuned to knock frequency.

For those intending to do the DIY, please read the link and help improve it. It is still missing the shopping list with Lexus/Toyota part numbers. The process is pretty time consuming.


Salim

Cooldaddy

I agree I've been reading your DIY post and my thing in the whole deal is this I just hate to spend the money I just put it in the shop for the water pump 2 coil packs and changed the plugs. Now I have to yank the intake off and could've changed the plugs myself and I hope I can salvage the antifreeze I just put in it plus I need tires lol. But I'm going to order all the oem and change it cause the $100 of 100 octane gas to try to clear it didn't work. But oh well. I want to thank you for the write up and I will be using it. And all the pics. I will be ordering either later today or tomorrow. So that I uunderstand the wire harness that everyone says is just the wire that goes from the knock sensor to the actual harness and I will need 2 since I'm changing both sensors. I will change the hose as well. And ordering a complete gasket kit cause I don't know what I will need rather have it n not need it than need it and not have it.

mikemacch

Well 4 years later I just sold the car. After I changed the knock sensors I never got another p0330 for 50000 miles. Seems like changing them did the trick.
I did get every oxy sensor go bad though. Seems like the same problems appear in these cars, THE FORUM IS GREAT in helping to keep them running as well as they do.
I now have a 2010 RX350, love it.

Cooldaddy

Wow change knock sensors changed wiring harness and for you guys out there it's just one harness for 2 knock sensors change your intake gaskets and change the hose also I changed the front and rear vvti sensor and 2 o2 sensors. Keep in mind this is because of codes being thrown out. All that changed and driving to Cracker Barrel with my wife n daughter and the sob engine light comes on again to tell me the cat converter needs to be change guess what's not going to happen til inspection time.

Bobster999

This is why I won't keep pouring money into an old vehicle. Yes I like my ride and plan to keep driving her. That said, I will always try to keep her running as cheaply as I feel comfortable with doing. These vehicles are costly to maintain and repair as they age. I don't feel its a good or a wise price to pay. I cant even use the word "investment" as it does not apply. All the money you just poured into her and something else pops up. This is what happens to virtually all older luxury type vehicles. They turn into money pits. If I were to fix everything at factory specs, I may as well sell the car and move on. Unless you have plenty of money to spend and just love your car. Good luck!

salimshah

preamble: This post should be considered as a member post and NOT as moderator ... remember I am a member too. When it comes to differing opinions my post does not deserve special merit and if in the discussion any one think I am using 'moderator privileges' please post or send me PM or even reach out to other moderators.

I humbly disagree with you. Yes there can be lemons and neglected vehicles but once any one goes down the slippery slope of 'just keeping the machine on road', the problems start snowballing. People mess up the logical trouble shoot process and tiny traps are placed all over the vehicle. I am on other end of the spectrum ... do the thing correctly and if one thinks it is time to move on to another vehicle .. do so, but dont pass on a trouble bucket to a fellow human being. Please do not infer that I am saying that you, bobster99, would do so, I am simply stating that in used vehicle market, such practices are frequent. We end up being our worst enemy.

Parts and labor are expensive. Usually labor is more expensive and may not be qualified. Forum such as this provides collective wisdom and if applied right we as owners can save lot of money. I am all for such savings and doing the things per spec. If you ever look at a failure analysis report, most of the time it will lead to something that was not done right.

On a lighter note (but more philosophical), many years ago when I was still a student, my roommate and I had a discussion on ... Are machines made to serve humans or humans made to serve machines?

Salim

Bobster999

This is where we can agree to disagree to some degree. This is why we all should not be shy about offering our opinion on things. I also dont think its cost effective to own and maintain an older luxury car unless you can at least do the needed work yourself and get it properly diagnosed the first time and not throw parts at it. Also you need to know when to use OEM and when to go aftermarket with parts. When to go used or new etc... One should also be aware that many parts are not critical and you can circumvent some of them without repercussion. Some parts are overkill. For example, since this is a knock sensor thread, My belief is that my car dont need 2 sensors. Very few cars use 2 especially older ones. If there were a real reason that my car started knocking because of pre ignition, it would not just happen on one side of the block unless maybe something extreme like the timing belt was off a tooth or more. With normal driving there should be no problem at all. I understand some people that dont know much about this will be afraid, but do 30 minutes of research, if you still dont feel comfortable, then go ahead and drop the money to fix it "right". This is just my opinion, i suggest that everyone has to do what you feel comfortable with and can afford to do. G/L

Cooldaddy

Allow me to just say maybe I have confused you by complaining about the rx300 with all being replaced. First the work of knock sensors and vvti sensors was done for around 750 and yes oem parts. Could I do it myself sure could. But my time wasn't worth the hassle. I look at it a bit different as well. I could by a 50,000 car off the lot or buy a good used one. Personally better to buy a used one atleast then you know the problems if any and have a better educated buying process. Acura and Lexus are luxury cars but will whoop any American pos out there. I bought the rx300 used in good shape but I believe neglected. I want to thank everyone that contributs to the forum. I found the thread very helpful.

LexusGG

My wife's is having the same issue now... A big pain!!! Not shifting to next gear.... RPMS rev up to near 5k at 65-70 mph...
Going to check out this week. Will post afterwards the results

Kauz

I'm in the process of replacing both knock sensors on our 2000 RX300. Does anyone know what that chalky plaster looking stuff is under the bypass hose (under lower intake manifold)? I've seen it in pictures in other posts as well, so I know it's not just my car.

I scraped it off and vacuumed it up, but it just didn't look like dirt. It seemed more like something that had disintegrated and accumulated from the heat.

For those who have done this DYI, any ideas?

carguy07

I would guess it's coolant from a small leak.