Fighting P0330 in a 2000 RX300
 

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 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?

Ground connections clean?

How cheap were those knock sensors? I broke the OEM sensor in my dad's s2000 so we decided to see if an aftermarket $7 one would do. It didn't, knock sensor code popped up. More than $100 later, it is fixed now.

What i'm thinking this might be is carbon build up on the pistons effectively raising the compression ratio above OE spec to the point where the ignition maps are too advanced. How about running a compression test?

Where did you get a knock sensor for $7? I spent $85 for one for my Forester.

It worked, though.

Can't believe I didn't think to check this. I just ran out and had a look with my multimeter, but all the ground straps were reading no resistance from one terminal to the other. Also checked between various points on the engine and body to the negative battery terminal, but found no problems.

There is that electrical corrosion gunk all around the positive battery terminal. I'm thinking of hitting that with baking soda+water, but please tell me if that's not a smart idea.

I got the Beck/Arnley sensors at $78 each.


I'll ask some people I know if any of them have a compression gauge. Last 4 tanks have been premium (but car can take 87) and we put Techron in the last tank and Seafoam in this tank. Again, also did the Seafoam Spray can at the throttle body but no effect. Some guy on the Lexus forum had the same issue and poured 4 cans of Gumout into 4 consecutive gas tanks and the light went out. I bought that stuff and we will do that going forward, but not driving it much because of all the problems so that could be a while.

Current Plan:
- Get access to a compression gauge
- Diagnose & fix the coolant leak in passenger compartment (probably heater core)
- Baking soda + water the positive battery terminal??

Thanks for help every1, please let me know if I'm missing anything.

Then smear post and connector with petroleum jelly before reassembly.

Might be a similar problem that I'm avoiding helping someone with on a 1999 Lexus ES300.

From what I've read, aftermarket knock sensors don't work. Solution is to buy OEM and probably eat the cost of those junk aftermarket parts.

I don't remember, it didn't work though so does it matter? :rolleyes:

I had trouble with a knock sensor because there was some corrosion on the block where the sensor mounted. After cleaning the block where the sensor mounted it started working correctly.

I want to make sure I never purchase parts from them!

Knock sensor codes come in two varieties
Knock when none expected
No knock when expected

Also, as the knock sensor generates its own voltage, very little current flows through the wiring and it's extremely susceptible to noise. Make sure the shielding is intact and grounded properly

Found water leak, it's where I thought it would be, tube going to heater core at the firewall. Waiting until engine cools then I'm going to have at it.

Fixed water leak. Rented a compression gauge from the auto parts store.

What all do I have to disconnect to make sure I don't damage the engine before I try testing it? Obviously the ignition coils will all be disconnected.

Compression looked good on all cylinders, highest was 165 lowest was 152. Going to take apart the upper part of the car again to get back at the knock sensors. Will test for corrosion on the block and shorts within the sensors themselves.

Also, unless anyone thinks it's a bad idea, while I still have the spark plugs out maybe I can spray some carb cleaner down in them to loosen some buildup if there is any, but I kinda doubt its bad at this point.

Compression sounds fine.

If you are going to loosen buildup, make sure you get it all out. You don't want it coming out when the engine is running.

Any tips on that? I've never done this before.

Air intake chamber is removed once again. I used my multimeter to perform 2 tests on each knock sensor, both passed both tests. However, I think I'll replace them both anyway with new OEM ones and just eat the cost.

Anyway, before I do it, is it safe to spray carb cleaner into the cylinders through the spark plug tubes? Also the valves are exposed right now... is it safe to hit them with that stuff, or will it cause problems when I start the engine in a week when it's all put back together?