Plus1RX

Hi everyone. I've been very active on other marque forums and frequently consult this one, but haven't needed to post. I guess we've been lucky with our '04 Rx330 so far. (124K miles)

We now have the infamous P0328 code plus the VSC warning light. I've cleared it several times, disconnected the battery and greased the gas cap but it only stays off for a short while.

I've done quite a bit of searching here and am zeroing in on two possible reported explanations:

1) The mysterious connection between the brake light switch and error lights that some swear is responsible for many codes, or
2) There actually is an error from the knock sensor - possibly due to coolant leaking on the wiring harness.

I'm afraid number 2 is winning because we do seem to be losing coolant slowly and using a borescope camera I can see a good deal of orange "stuff" in the valley under the intake manifold.

That said, I'd love to find out that a new brake light switch would cure whatever this is. I'm reluctant to go with aftermarket based on input here so this swap would cost about $100 in exorbitant Lexus part pricing. Maybe cheaper if there's a trusted online source for OE parts - is there? And if anyone can confirm that a 4Runner switch is the same that would be good also.

Regardless, I'd appreciate any thoughts on whether it's worth the time and $ to replace the switch before jumping into serious disassembly.

Thanks in advance for your help.

Ron

Plus1RX

Answering my own question in case it might be helpful to others down the road. Turns out I did not need to replace the brake switch, nor resort to expensive or time consuming intake manifold R&R (yet.)

Helped with input found in another thread, I was able to find and cut the wires going to the faulty knock sensor and divert them to a new sensor mounted on the engine in a location that is accessible. $25 in parts and it worked like a charm. I can post more info and photos if anyone is interested.

We'll someday need to fix the minor coolant leak under the intake manifold and will restore the proper sensor arrangement at that time. But it's a slight seepage and not worth a $1,500 repair tab (or 5-6 hours of my own time) to go after just now.

Ron

jeffro22

Hey Ron, =we have a 2004 rx330 that is throwing knock sensor codes. I would love to see how you cut the wires and remounted the sensor

thanks

chiliman

Ron,
I also have an "04 rx330 throwing off a P0328 code & would love to see photos of how you repositioned the knock sensor.
BTW - did you also have check engine & VSC lights on & did your knock sensor fix turn those lights off?
thanks
Chiliman

Plus1RX

Let me put some photos together and also look up the link(s) that helped me with this. Will post once I get it together. In the meantime:

Jeffro - you said codes. Does that mean you have both knock sensor codes? P0328 and P0330, or just one?

Chillman - yes, either knock sensor code will turn on the CEL - and from what I've read, whenever there is a CEL light, for some reason it also lights up the VSC lamp. This also puts the ECU in "limp mode" - which as you've probably noticed makes the car drive like a slug. And yes; once I was able to get a good connection to the replacement sensor, they went out.

Ron

matts6887

if it were me i would not bypass the sensor because if u do bypass it and there really is a issue with one of the sensors then u may not know it.

chiliman

just today found that negative battery cable was loose. After tightening ( I had to buy a $2 thimble like “shim”at AutoZone) all check engine lights went out & diagnostics now do not throw off any codes! This simple fix may help others.

Plus1RX

That is indeed good advice, and I'm not advising anyone to try this without knowing what they're getting into - more about that in a subsequent post. But to be clear, in this case I didn't bypass it, I just switched over to a new replacement sensor mounted on the engine "sort of" close to the original - which can't be accessed without major tear down of the intake manifold. I suppose there's a slight risk this location won't detect knocking as well as the original location does, but I think the odds are good that if one bank of cylinders has a knock then the other will as well - and there's a good original sensor still in there. Also, unless you get some very contaminated fuel, knocking is not a real big risk in these engines unless something else goes wrong (e.g. ECU spark timing, crank position sensor, valve timing adjuster, etc.) and in that case, there will be other codes thrown I would think.

Finally, not to beat this much further, there are several threads on this topic and many people who pulled everything apart (as I'll do at some point) confirm their issue was coolant seepage-caused corruption of the sensor connector. Once I got access to the wiring harness I was able to check resistance and both my "good" OEM front bank sensor as well as the new replacement read 0.2 Ohms, while the wires going to my "bad" sensor showed 15 times that. FYI - here's a bore scope photo of the built up crystallized coolant "mountain" in the valley between the banks (where the knock sensors and connectors are mounted.) At first I thought a large family of mice had built a nest in there. Now I just need to keep my fingers crossed that the other connector buried in there somewhere stays uncontaminated. Not sure where I'd mount another replacement.

chiliman

OK, the CEL popped back on about 15 minutes after battery cable was securely fastened - reran diagnostics & still Knock Sensor - P0328. So Back to square 1.

chiliman

Ron,
Yes, car is sluggish & highway gas mileage has dropped from 23 to 19 mpg. Do you think replacing both knock sensors will solve sluggish engine problem?
Thanks,
Chiliman

Plus1RX

Yes I was wondering about that. Each time the battery is disconnected and reconnected, the ECU runs a new test cycle on power up to check all inputs. During that time there is typically no CEL. Once all the monitors are reset, any errors that remain will throw a code and turn on the CEL.

In answer to your 2nd question, yes, everything should return to normal once the ECU is no longer getting a fault signal from the sensor, causing it to severely limit revs, retard the timing and do other annoying things.

DennisMik

The knock sensor is there to detect if the engine is not running properly (i.e. knocking). The P0328 may be a valid problem, not just a bad knock sensor. It may be difficult to determine which is true. Do you ever hear the engine pinging?

chiliman

No pinging. No overheating. I’ve owned this Rx330 since ‘07. 160k miles. Have had multiple diagnostic tests & only thing that pops is P0328. Just got back from 3000 mile road trip & all was fine. No CEL & no acceleration problem. Now CEL, VSC, bad acceleration & mpg down ~20%. If it were oxygen sensor- wouldn’t a code show it?

DennisMik

I would expect an O2 sensor to throw a code, but there are no guarantees. It would be rather rare to not get a code. A bad upstream O2 sensor will cause poor gas milage but if you have the knock sensor code, that will cause the ignition timing to be retarded, which will reduce gas mileage also.

Since it seems that the engine is running OK, then you may have a bad knock sensor. You can check the ohms of a knock sensor, but I don't know what the ohms reading should be.

Plus1RX

Both my "good" sensor and my newly purchased replacement read 0.2 Ohms. The one that was throwing the error code read 3.0 Ohms. If you want to remove the glovebox and disconnect the connectors at the ECU the measurements can be taken there. I took mine from the connector on the engine once I was able to access it.

I promised more info on my sensor replacement project and just about have that put together. I hope to be able to post later today.

Ron