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Boxer54
Boxer54, ASE Certified Technician
Category: Lexus
Satisfied Customers: 1681
Experience:  Over 15 years experience in automotive field - ASE master technician and L1 advanced certification
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Get check engine kight...Knock sensor 1..full gas tank, rare below 1/4

Resolved Question:

Get check engine kight. Code is "Knock sensor 1, bank 1". The strange part is
that it happens frequently with full gas tank, rare below 1/4. So, is it really
the knock sensor, or something simple? Yes, gas cap is good.
Submitted: 3 years ago.
Category: Lexus
Expert:  Boxer54 replied 3 years ago.
Thank you for trusting Just Answer with your Lexus question. There are several codes which refer to the knock sensor and each could be tackled in a different manner. What is the code number you have for this?

Edited by Boxer54 on 9/16/2010 at 9:24 PM EST
Customer: replied 3 years ago.

My reader just says the Knock sensor, always 1, bank 1. and does say

"circuit malfunction" My reader does not give actual number code.

I do know when light is on, car will not go into OD. I do have an older

reader that gives number code. Could use that when it happens

again.

Expert:  Boxer54 replied 3 years ago.
Really, I will need to know the code number to best help you with this. If you have not cleared the code, you can probably still retrieve it. Also, if need be, in most states, you can go to your local chain auto parts store such as Autozone and have the codes read for free.
Customer: replied 3 years ago.

I had to pull over and erase as it happen as I pulled onto the freeway. Didn't want to

run at high RPM that long. Will have to wait till next time. I do have an Autozone

close, and can also put the reader that has the codes and code book in the vehicle.

 

Sigh. WAS a mechanic when things were simple. ;)

Expert:  Boxer54 replied 3 years ago.
You can log in and add to this post at any time.
Customer: replied 3 years ago.
Will do.
Customer: replied 3 years ago.

OK. To speed up the process, I just filled the gas tank. Got light right away.

Got two codes this time. PO325 and P1130.

Expert:  Boxer54 replied 3 years ago.
Refueling has no affect on these codes, so it was coincidental. For now, as per the service manual, we are going to ignore the p1130 code and go straight after the p0325 code. This is the code for the bank 1 knock sensor. This is the sensor on the right bank. There is a 4 pin dark gray connector right at the back of the rear cylinder head. The wires run under the intake manifold and these are the wires for the knock sensors. Heres how to go about diagnosing this. It will require you to either make some jumper wires to go in between the 2 parts of this connector, or remove the pins from one side of this connector and swap the pins closest top the lock tab. Using either method, the goal is to connect pin 1 on one side to pin 2 on the other and pin 2 to pin 1. What this will do, is , after clearing the codes, and retesting, tell us if the computer is reading normally, or if there really is a prob;em under the intake manifold. With the wires swapped, if we get the same code, we need to dig a little deeper into this concern. If we get a P0330, this means that the computer is reading correctly and we have either a wiring issue under the manifold or a problem with the knock sensor. If this is the result, the intake manifold will need to be removed to proceed. Once removed, it will probably be really easy to see the problem. Almost every time we see this code, we find that a small critter has crawled and or nested under the intake manifold and has chewed on the wiring. So, the wiring will need to be repaired.
Customer: replied 3 years ago.

I agree with your answer. But, am thinking I might as well just replace knock sensors

and the wiring harness since they are conveniently placed under intake anyway. Do

wonder why the light has not yet come on under 1/4 tank though... Any particular

strange things with pulling intake, given I am/was a mechanic? (OK, it was on

Fords ;) )

Expert:  Boxer54 replied 3 years ago.

Replacing the knock sensors are a pretty good idea considering the work involved. I wouldn't advise replacing the harness, but repairing it, as the replacement part cost is really going to be too high. The only kicker to the intake manifold removal is the plenum has a couple of brackets on the back by the firewall and getting to the bolts to remove them is pretty tricky. Also, there is a ground wire right on the back between the plenum and the firewall. Other than that its pretty straightforward.

Boxer54, ASE Certified Technician
Category: Lexus
Satisfied Customers: 1681
Experience: Over 15 years experience in automotive field - ASE master technician and L1 advanced certification
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