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Discussion Starter #1
Y'all know lots about cars, maybe someone has some Insight on what I can do about this problem with a Lexus...

tl:dr;
- P0330 on 2000 Lexus RX300 275k miles
- Replaced both knock sensors and wires
- Code went away for 50 miles
- Back now and comes back almost every time you drive it
- Tried Seafoam in the tank and Seafoam Spray into throttle body
- Still get P0330

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My dad's trying to sell his Lexus RX300. Bought new in 1999 it's a 2000 model year car, now sitting at 275K miles.

P0330 is Knock Sensor Circuit bank 2 malfunction. I replaced both knock sensors with new ones from RockAuto and I replaced the wire that goes to them.

Car drove fine for 50 miles, but then I started getting the P0300 again. Also, coolant leak at same time, I think I may have damaged one of the tubes going into the heater core when I did the knock sensor repair. Leak is kinda slow, been topping it with water, there's no danger of freezing weather down here in Georgia at the moment.

After the P0330 came back I put a can of Seafoam in the gas tank (it's been running premium btw) and I tried the Seafoam spray stuff that you spray into the throttle body, used maybe ¾ of a can of it in there while my dad revved the engine. We let it sit a while then I went and drove it pretty hard for a few miles as recommended on the can.

P0330 keeps returning. Not sure what to do, as this will cause it to fail emissions thereby greatly impacting resale value.

Any ideas?
 

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I'm not a Lexus expert, but were the sensors from Rockauto OEM parts, or were they aftermarket? It seems from what I've read that if the parts aren't the original brand used, it might not work as it should. I don't mean to be insulting, but is it possible that the wire got reversed when replacing it for the two sensors? Both of these possibilities I read about on Lexus forums. Again, I'm not an expert, but it might be worth looking into.
Best of luck!
- Tim
 

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Discussion Starter #3
Hi, not insulting at all.

Wires were not reversed, but in this case it wouldn't matter. A fix some people do is they splice the wires at the ECM.. for example if sensor for bank 2 is throwing the code they cut its wire near ECM connector and splice into the bank 1 sensor so the bank 1 sensor is the only one sending a signal.

I did go with aftermarket sensors but I'm reluctant to suspect them at this point. Reason why is the code did not show up for over 50 miles after the knock sensor replacement was complete. I think that means I did SOMETHING that solved the problem. And then eventually the fix was no good anymore or something like that.

Or at the very minimum the sensors and new wire were good for 50 miles but then went bad but that doesn't really mke sense to me that they would die that fast. Maybe there actually is knock?
 

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Hi, not insulting at all.

Wires were not reversed, but in this case it wouldn't matter. A fix some people do is they splice the wires at the ECM.. for example if sensor for bank 2 is throwing the code they cut its wire near ECM connector and splice into the bank 1 sensor so the bank 1 sensor is the only one sending a signal.

I did go with aftermarket sensors but I'm reluctant to suspect them at this point. Reason why is the code did not show up for over 50 miles after the knock sensor replacement was complete. I think that means I did SOMETHING that solved the problem. And then eventually the fix was no good anymore or something like that.

Or at the very minimum the sensors and new wire were good for 50 miles but then went bad but that doesn't really mke sense to me that they would die that fast. Maybe there actually is knock?
Yeah, that's a good point. It wouldn't make much sense for the sensor to fail so quickly. I would head over to the Lexus forums if I were you. I found a couple threads there covering the topic. I didn't find a definite case plus solution, but you might be able to get some ideas. On another site I found some troubleshooting for the ECM. Maybe an online service manual is available for download? These are just some avenues I would consider pursuiting.
- Tim
 

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Do you have a service manual for this vehicle? You can test the knock sensors fairly easily using the procedure in the manual. I also have owned quite a few Lexus Vehicles. They are such a joy to work on aren’t they!?! (Sarcasm). Anyways it’s either your sensor is bad or your wiring going to it is bad. You can ohm test the wire from the computer to the sensor. Or just buy the wiring harness and sensor and call it a day. Get an OEM one though I think they are only $100 and you won’t have to do the 4 plus hour job again.

Good luck!
 
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