Knock Sensor Redux

[lexis lexus]

Hi all,

94 es300 w/ 111k. Throwing codes for both knock sensors. Went to yanker yard and pulled out 2 from a '92, wiring and connectors crumbled in my hands when I got the intake manifold off. Jeez, must be like a pottery kiln in there when the engine's hot.

George's suggestion in mind, I went home and mounted one to the front driver's side bolt/nut holding down the intake manifold, wired it up to the connector behind #5. Still threw the codes. Tested all wiring, including from connector to computer, and all good. Tested ks per fsm, (but I don't have an oscilloscope....

So, either 1) George's idea about externally mounting a knock sensor is faulty somehow, 2) both knock sensors I got from the 92 are bad, 3) knock sensors I got are not compatable w/ the 94, 4) mounting the ks where I did is not adequate, or 5) some other s-.

Thoughts?

Lexis

[George_Jetson]

Is there any possiblity that you could get a borrow a oscilliscope? Since the knock sensor is pizo-electric, it will put out a signal even with no wire connected to it. I have not personnelly tried the external mount thing, (read it on another forum), but it sounded good to me. did you use a fairly heavy bracket to mount the sensors?

Do you have any friends that drive a lexus/toyota of similar year? If so, (and you do not have a scope), try measuring the output with a DVM on the AC volt scale. See what a good sensor reads. I am rather tied up now, but if you can wait a few days I can measure the output on my car. The AC volts scale will not tell you exactly what the reading is (a scope would tell you exactly), but it would give you a good relitive reading that should be more than adequete.

For my 2 cents, I would assume that the knock sensors are more than likely close enought between the years, they should work.

[lexis lexus]

Is there any possiblity that you could get a borrow a oscilliscope? Since the knock sensor is pizo-electric, it will put out a signal even with no wire connected to it. I have not personnelly tried the external mount thing, (read it on another forum), but it sounded good to me. did you use a fairly heavy bracket to mount the sensors?

Do you have any friends that drive a lexus/toyota of similar year? If so, (and you do not have a scope), try measuring the output with a DVM on the AC volt scale. See what a good sensor reads. I am rather tied up now, but if you can wait a few days I can measure the output on my car. The AC volts scale will not tell you exactly what the reading is (a scope would tell you exactly), but it would give you a good relitive reading that should be more than adequete.

For my 2 cents, I would assume that the knock sensors are more than likely close enought between the years, they should work.

I mounted it w/ a 1 x 3 x 1/8 inch piece of angle bracket steel, nice solid mounting, even found a bolt to secure the sensor on. I agree the sensors are prolly all the same, seems like it looking at pix on ebay.

I don't have a clue where to get an osc scope. I wonder if iphone has an app (lol).

Why AC volts? Will try this next. I tried DC volts and got a very mini reading maybe (0.1 v dc), no measurable ampers...

Think I'm going back to the yard, where they have a 95 and work on it.

LL

[George_Jetson]

Sounds like you have a decent mounting bracket. You want AC volts because of the nature of the signal that is coming off the sensors. It looks like a high speed sine wave ( not the correct term, but the closest that I could think of). Ac volt meters are designed to read this type of voltage. DC is for a steady state voltage, and is fairly useless for this particular measurement.

[fpny]

I was wondering, what kind of problems or damages (if any) one would do to the engine if you driving around with the CEL and the P0330 knock sensor code on. As far as I can gather, the P0330 code indicated that there is a problem with the sensor (the ECU cannot read the sensor output), but the engine is not really knocking. Since the computer cannot read the sensor, so it defaults to a save mode operation. If you continue to drive under this condition, does it really do anything to the engine?

[lexis lexus]

I was wondering, what kind of problems or damages (if any) one would do to the engine if you driving around with the CEL and the P0330 knock sensor code on. As far as I can gather, the P0330 code indicated that there is a problem with the sensor (the ECU cannot read the sensor output), but the engine is not really knocking. Since the computer cannot read the sensor, so it defaults to a save mode operation. If you continue to drive under this condition, does it really do anything to the engine?

I doubt too much major damage, but from my search in the archives, someone mentioned that there are 2 default modes, light and heavy so to speak, with the heavy knocking out overdrive and retarding timing significantly, dropping mpg and potentially damaging valves due to early detonation (to keep temp down...to stop the non existant knock). I haven't heard one knock, despite 87 octane, but the computer just defaults to a mode which says (illogically) "there is no signal, so just in case there's knocking but we can't sense it, we'll just default to a mode that will be 'safe' in the event of knocking..." Not too clever given that most of the time the loss of signal is due to wiring, and never due to too much knocking!

I went back to the upullit today and got two more K sensors, this time from a matching '94 es300 so there shouldn't be any question about compatability. Will mount one tomorrow and see. Learned a lot about getting in there....

To be continued....

[fpny]

As far as mpg is concerned, I took the car on a long road trip last weekend and drove over 500 miles on the car with the CEL and the P0330 code on. When I filled up the car at the gas station, I got 418 miles on a tank of gas and I put in 14.318 gallon of gas. It came out to be over 29 mpg on this tank of gas. Beside feeling lack of power from acceleration from slow speed once in a while, the engine did not run any different than what it used to be before I had the CEL on. I wished I can find the CE1 connection on the wiring harness and connected both inputs to the ECU from the good sensor. Did anyone know where the EC1 connector located on the engine. I can't seem to find it from the wiring diagram that's on the 97 ES300 service manual.