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Chris (aka-Moose)
Chris (aka-Moose), Technician
Category: Car
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Experience:  16 years of experience
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The nature of it... Im not in front of the car diagnosing it

Customer Reply

Customer: replied 9 years ago.
1999 Lexus ES300. Codes P0171, lean bank 1, P0325 Knock 1 and P0330 Knock 2. No overdrive. Poor acceleration. VSC light on. Switched A/F sensor. Used donor knock sensor bank 2. No change.Replaced ECM, no change. Have been told there is a wiring harness problem. Research indicates knock sensors causing problem but not sure of how to fix. Require definitive answer from someone that has dealt with this problem. Thanks
Expert:  Auto Tech Guy replied 9 years ago.

Dbeck,

Definitive answer? Anything on a website like this is always "best guess," thats the nature of it... I'm not in front of the car diagnosing it... I dont know what else could be happening with it. It would be negligent of me to say "oh yeah its this!" at best I could say "its probably this!" That being said.

No overdrive or VSC= Normal, when you have a CEL they shut off

I think that it may be a good possibilty that there is a harness issue IF you replaced the ecu and knock sensor of a *known* good one.

Going forward with that knowledge its time to start performing some tests:

http://www.keepandshare.com/doc/view.php?id=370874&da=y

Causes of knock sensor failure->

 Open or short in knock sensor 1 circuit

 Knock sensor 1 (looseness)

ECM

Testing knock sensor:

Using an ohmmeter, check that there is no continuity between the terminal and body. If there is continuity, replace the sensor.

Next:

Time to check at the ecm if the knock senosor signal is even getting to the ecm:

Both are in connector e11 and are in PINS 27 and 28 (refer to above below)

http://www.keepandshare.com/doc/view.php?id=370912&da=y

It should be a pulse generated signal and would be best to have an occilliscope read the signal, if you have a good enough voltmeter it may have the function.

-If your test leads are long enough test for resistance over the wire, inside the engine comartment to the ecu terminal

*hint* back probe the ecm terminal with a needle or long bobby pin

I believe your going to find a break in the harness and will need to replace/repair it BUT CHECK IT FIRST. It is shielded wire, so dont put standard wire back in place of it if you do.

 

Good luck, I hope this helps. Good day.

 

-Auto Tech Guy