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Old 11-11-2019, 02:40 PM   #1
Colonel Ives
Scooby Newbie
 
Member#: 211558
Join Date: May 2009
Location: Seattle
Vehicle:
2002 WRX sedan

Default Knock sensor wiring - 2010 Impreza

2010 NA Impreza

I left the knock sensor plugged in and removed the intake manifold. In the process I ripped the pins out of the connector that connects to the knock sensor. So, both sides of the connector were still attached to the knock sensor, and the manifold harness had two wires with bare pins hanging out.

I was able to jam the pins back into their housing and reconstruct the harness-side connector, but now the car drives really sluggish. It's not throwing any codes related to the knock sensor. I suspect I have it backwards. I don't want to just go and swap the wires and see what happens without having a better idea of what might be going on.

Questions:

Can anyone tell me which wire is supposed to be on which side? A clear photo of an intact knock sensor and its connection to the intake manifold harness would be amazing. I have the FSM and it does say which color goes on which side, but I don't know whether the diagram is supposed to show the connector viewed from one side or the other, so it's useless to me.

If I put the wires in the wrong way and started the car, would that fry the sensor?

Could the sluggish performance be related to the knock sensor, even if the engine isn't throwing any knock sensor-related codes?
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Old 11-11-2019, 04:18 PM   #2
Gamil
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Member#: 220375
Join Date: Aug 2009
Chapter/Region: TXIC
Location: Clear Lake, TX
Vehicle:
2011 Outback Sport
Blue

Default

Sluggish performance could absolutely be due to the knock sensor. When the sensor doesn't work or if it's detecting knock, the ECU goes into limp mode with severely retarded timing.

I don't have a picture for you, but the two wires should be
1. Red Blue
2. blue White

Looking at the connector head on (the part that plugs into the sensor pigtail), with the tab on top, 1 is on the right, 2 is on the left. Enjoy my ascii art of what's in the FSM
Code:
       ___
 _____|   |______
|__2____|___1___|
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Old 11-14-2019, 06:43 PM   #3
Colonel Ives
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Member#: 211558
Join Date: May 2009
Location: Seattle
Vehicle:
2002 WRX sedan

Default

Well, dang. I confirmed that the wires are not swapped. It looked like one was not in all the way, so I pushed it in even more firmly, reconnected the sensor, confirmed the wires hadn't backed out, and put it all back together. Still drives like crap.

Maybe I damaged the knock sensor itself when I ripped the two plugs apart?

I should also mention that it was also throwing a P0028 the other day. Internet searches suggested that the VVL diagnosis oil pressure switches could have been damaged when I had the heads reworked -- the cleaning machine can screw them up. Resistance across each was 16 and 30 ohms. I went ahead and replaced both of them and cleared the codes and that problem went away. New sensors had 1.4 and 4 ohms.
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