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Knock Sensor


chelo

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Hello...i recently purchased a 2000 lexus rx300 with 84,000 km(not miles). Car was running great when i test drove it. However, after 4 days, the engine light came on. Immediately i noticed that the car lagged behind and would rev much higher to move than it did before. I got it checked out, and it ends up that the knock sensor was down. The certified Lexus mechanic told me to disconnect the battery for 2 seconds and see if the engine light turns off, and it did! The car was running back to normal.( no lagging or high reving)

However, the day after the light came back on. Immediately i took the car back to the mechanic and he changed one of the knock sensors for about $500.00. Car ran great for two days and then engine light came back on. Got it checked and shows the knock sensor again.

I don't know what to do now. Has anyone experienced this before and have any suggestions, please help!

I'm also only getting about 390 km on a full tank because it is reving high.

Thanking you in advance to anyone who can help.

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Immediately i took the car back to the mechanic and he changed one of the knock sensors for about $500.00. Car ran great for two days and then engine light came back on. Got it checked and shows the knock sensor again.

there are two knock sensors, one for each bank. it might be the other one thats causing the light to come on.

also you shoould have him check the harness that comes off the sensors, it gets connected to the main engine hearness around the thermostat housing area, just to be sure. Again this is based on the fact the engine is not knocking of course.. good luck :cheers:

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Immediately i took the car back to the mechanic and he changed one of the knock sensors for about $500.00. Car ran great for two days and then engine light came back on. Got it checked and shows the knock sensor again.

there are two knock sensors, one for each bank. it might be the other one thats causing the light to come on.

also you shoould have him check the harness that comes off the sensors, it gets connected to the main engine hearness around the thermostat housing area, just to be sure. Again this is based on the fact the engine is not knocking of course.. good luck :cheers:

Thanx so much for your feedback! i appreciate it! :D

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Immediately i took the car back to the mechanic and he changed one of the knock sensors for about $500.00. Car ran great for two days and then engine light came back on. Got it checked and shows the knock sensor again.

there are two knock sensors, one for each bank. it might be the other one thats causing the light to come on.

also you shoould have him check the harness that comes off the sensors, it gets connected to the main engine hearness around the thermostat housing area, just to be sure. Again this is based on the fact the engine is not knocking of course.. good luck :cheers:

Thanx so much for your feedback! i appreciate it! :D

Anytime, good luck with the car. :)

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what you should of done is have them change both sensor when he has everthing apart. i know it cost a little extra but it keep you from doing the same service twice. I had this problem before also which did cause the hight reving. im soo glad i got it fix.

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what you should of done is have them change both sensor when he has everthing apart. i know it cost a little extra but it keep you from doing the same service twice. I had this problem before also which did cause the hight reving. im soo glad i got it fix.

Thanx for the feedback...did you get both of them fixed? and had the light gone back on?

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Anyone know of a way to read trouble codes on an RX without an external code reader(tool). My old Dakota truck allowed you to pull trouble codes by cycling the ignition/acc switch three times and you'd be able to read the codes on the digital odo. Good thing too obecuase that thing had a lot of codes to read!

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Anyone know of a way to read trouble codes on an RX without an external code reader(tool). My old Dakota truck allowed you to pull trouble codes by cycling the ignition/acc switch three times and you'd be able to read the codes on the digital odo. Good thing too obecuase that thing had a lot of codes to read!

Can't do that on a RX, you need the reader. $40, is about the cheapest I have seen.

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Chelo.... Did you get the problem fixed??? I have the same problem. First they changed the MAF and the 2000 RX300 ran better but then another engine light.. this time they say KNOCK SENSOR open code. I didn't have time have them look at it.. so still have the problem.. please please post a follow up.

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Chelo.... Did you get the problem fixed??? I have the same problem. First they changed the MAF and the 2000 RX300 ran better but then another engine light.. this time they say KNOCK SENSOR open code. I didn't have time have them look at it.. so still have the problem.. please please post a follow up.

What's and MAF?... either way..had them both changed and car runs like a charm so far.....do the same, it's a common problem with these cars and toyota carolla.....hope ypu get it fixed.

Good luck

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I have a 2000 ES and had a similar problem. I had engine knocking under load and the check engine light came on as well as traction off. The transmission was reluctant to downshift also. I took it to the dealer and they replaced a knock sensor with a cost of $780.00 (luckily it was under extended warranty and it only cost me $75). On the way home the CEL came back on. After doing a search here, I discovered that the MAF for the ES is defective and periodically needs to be cleaned. It cleared up my problems for me. Do a search on how to clean the Mass Air Flow sensor. It may save you a lot of money and it is very easy.

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I have a 2000 ES and had a similar problem. I had engine knocking under load and the check engine light came on as well as traction off. The transmission was reluctant to downshift also. I took it to the dealer and they replaced a knock sensor with a cost of $780.00 (luckily it was under extended warranty and it only cost me $75). On the way home the CEL came back on. After doing a search here, I discovered that the MAF for the ES is defective and periodically needs to be cleaned. It cleared up my problems for me. Do a search on how to clean the Mass Air Flow sensor. It may save you a lot of money and it is very easy.

Yes I wish i had done a little research on the Mass Airflow Sensor... I'm sure my "old" one is good if i had learned about cleaning it. Very easy to get to also. My "knock" was resolved by the MAF change out. So I'm wondering if these Knock Sensors really are bad or not. The dealer said it was an "open" circuit for the knock sensor. They seemed to think is was a wiring issue. My RX300 runs good, but has the downshift problem and doesn't easily go into the last gear, so has high revs if try and go over 55-60 mph. I hate to have the knock sensors replaced if they really aren't bad. I only had 48k on my lexus, but was over 4 years, so they wouldn't cover it under warranty. :(

Is there anyone who can help me with the location of the wiring for the knock sensors?

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  • 3 weeks later...

Hey, my daughter's 200 RX300 with 58K miles had check engine light and wouldn't go into overdrive, we changed the MAF sensor (tried to clean first) and it upshifted then check engine light came back on did a code read and it showed misfire in cyl 6, changed plugs, took 3 hours and this cleared up misfire, drove again and check engine light came on again, shop said KNOCK SENSOR code, this seems strange. Feeds to sensor has power, ck eng light comes on after a couple mile drive if it is reset. Anyone know howto fix this situation without paying $500. every time light comes back on?? Is one of the Knock Sensors bad? Many thanks, these check engine lights are a real problem with state inspections not passing now.

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  • 3 weeks later...

I just had my car looked at today. They said they can't check all of the wiring to the knock sensors because the intake manifold is in the way, can't disconnect the pigtails from the knock sensors. So the wiring can't be checked until the intake is off. This repair shop said 90% of the problems with knock sensors have been the wiring harness. I've decided to have them do the work. Will have them order the wiring harness and intake gaskets, but I will bring in the two knock sensors. If only the wiring harness proves to be bad then I'll return the two knock sensors. I think the wiring has one main plug then pigtails to two separate plugs going to each knock sensor. Price about $65.00 for the wiring harness. They say it is 4 hours labor for the job.

This web site below had the lowest price ($143 -partsamerica.com) for knock sensors of about 4 web sites I looked at. They seem to be associated with several autoparts chains including Kragen, so I think I will check prices at the local Kragen Auto Parts. Local Autozone quoted $190 each.

http://www.partsamerica.com/ProductList.as...=Knock%20Sensor

Will post again if I get the work done soon.

Hey, my daughter's 200 RX300 with 58K miles had check engine light and wouldn't go into overdrive, we changed the MAF sensor (tried to clean first) and it upshifted then check engine light came back on did a code read and it showed misfire in cyl 6, changed plugs, took 3 hours and this cleared up misfire, drove again and check engine light came on again, shop said KNOCK SENSOR code, this seems strange. Feeds to sensor has power, ck eng light comes on after a couple mile drive if it is reset. Anyone know howto fix this situation without paying $500. every time light comes back on?? Is one of the Knock Sensors bad? Many thanks, these check engine lights are a real problem with state inspections not passing now.

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  • 3 weeks later...

Hi I did finally get this work done...

I found a local shop that someone recommended and convinced them that I wanted to get the two knock sensers myself in case they were not bad then I could return them. They quoted 4 hours labor I think.

I got the kock sensors from Rockauto.com for $257.07 total.. a really good deal i think.

The service guy got the electrical pigtail.. he told me about 65.. but in the end it was only $35

Also the gasket was only $11.99...

I ended up paying for 3.5 hours labor.. (he said the book says 4.5, but he had chaged me for 1 hr already so gave me some credit)

So the total was $257 + $35 + $12 + $283 = $587

Everything seems to be ok.. no engine light yet and shifting is good..

Service tech said it was a bit of a pain to do. He also said the knock sensors I got were of good quality. (i think they were Standard Auto)

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  • 2 months later...

Hi, I think I got the same problem on my 1999 RX300. Where can you get the harness and the gasket? What gasket is that? I found the knock sensor for about $130 a piece.

Thanks in advance.

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  • 2 months later...

Hi, I think I got the same problem on my 1999 RX300. Where can you get the harness and the gasket? What gasket is that? I found the knock sensor for about $130 a piece.

Thanks in advance.

My 2000 has the same problem: P0330 (knock sensor out) and not shifting to overdrive (high rev over 4oMPH). Me 2 want to know where to get the gasket and harness?Rockauto has the gasket for $70 :(

...

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  • 2 months later...

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