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Guest Message by DevFuse

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Knock sensor problems

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4 replies to this topic

#1 aldin20



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Posted 16 February 2013 - 02:27 AM

Hey everyone, ive been searching online everywhere but to no avail.

i have a Subaru heritage (liberty) 1999 3rd gen 2.5 litre. EJ251.


i have had the check engine light on since purchase and have been told by previous owner that the knock sensor needs replacing, so i got my mechanic to verify which turned out to be true, so i replaced the knock sensor and the check engine light disappeared and reappeared ten minutes later. So we checked the ecu and and deleted its code history, then we expected the light to finally go away but it didn't. Fast forward 2 weeks later and i'm driving and ten minutes into my drive it goes away for the whole 20 minute trip. i return to my car and start it again and the light has reappeared. We checked to see if there's any damaged cables, but there wasn't.


I love my suby and i want to customize it but i cant until i know that everything internally is tip top shape. Also there has been an oval shaped ring leak where i park the car. I also smelt gas leaking from the car and i cant tell from where. Last but not least, the car takes a few seconds approx 5-10 to start. I think its the fuel filter, the pump work but maybe its clogged a little. but if anyone could give me a solution to the problems id greatly appreciate it.


Thank you.


P.s the code the computer continuously spat out was PO333 Knock Sensor 2 circuit high input (bank 2)

Edited by aldin20, 16 February 2013 - 02:30 AM.

#2 Cougar


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Posted 16 February 2013 - 05:29 AM

Have you checked sensor wire to make sure that another wire hasn't bridged on to the connection? There are tests that could be done to make sure that hasn't taken place. It is kind of doubtful that has happened though. It really seems like there is too much signal getting to the ECU. You might try removing the sensor and try placing some teflon tape used for pipe threads to see if that makes the sensor less sensitive to the engine vibrations. Another thing that might help is adding a 100k ohm resistor in series with the lead but I would only do that as a last resort.

#3 aldin20



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Posted 16 February 2013 - 06:29 AM

My friend "the mechanic" had all the wiring checked. The little wire attached to the end of the plastic cap that connects to the knock sensor came off the plastic cap and we fixed that although everything's fine. I'm just so lost. It went away today and returned once I turned off the car. The engine ran smoother when the light went off. Regardless ill talk to him about your other two ideas but I'm not sure what hell say. It's always the little things that kill you :/

#4 rboyd



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Posted 16 February 2013 - 11:44 AM

smelling gas and check engine light at the same time.  I'm no mechanic but I would check everything related to fuel, from the filler cap through the tank, fuel lines, pump and filter (as you mentioned) to the injection system.  any of these could turn that light on and none of the repairs would be that major

#5 1 Lucky Texan

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Posted 16 February 2013 - 12:42 PM

seems like loss of pressure from a fuel leak would lead to the longer than normal start as the pump must fully pressurize the rails.. Find and fix the fuel leak and I bet starting will be more normal.


I also wonder if carbon buildup in the engine could be confusing the knock sensor with some occasional pinging. maybe try a SeaFoam treatment.

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