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Discussion Starter #1 (Edited)
Hey guys I’m back and decided to make a fresh post now that I have a proper vag tool.

2001 Passat 1.8l AWM

knock sensor is reading low voltage.

I’m on measuring block 26 and sure enough knock sensor is reading low voltage.

Cyl 1: .23v
Cyl 2: .23v
Cyl 3: .35v
Cyl 4: .35v

When I rev the engine cyl 1 and 2 stay the same or not much change at all in voltage.

cyl 3 and 4 increase according to throttle position moving anywhere from .35v to 10+ volts.

Anyone got any ideas where to start with this?

Thanks
 

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refresh my memory did you check connector "bonnet" at (sensor) to connector at ECM for wire continuity between sensor and ecm ? apologize in advance for asking if redundant.....
 

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Discussion Starter #5
No problem. I’ve checked all wiring for continuity and shorts from Ks bank 1 to pins on ECM and I’ve checked all wiring for ks bank 2 as well. No shorts or continuity at all which meant wiring harness is good.

I’ve replaced the knock sensor on bank 1 with a brand new sensor. I’ve even pulled a used from from a junkyard and tried that.

Last place I left off was trying to determine how I can pull Immo codes to swap an ECM but I figured now that I have a proper vag tool maybe we can narrow down to what the actual issue is here.
 

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Discussion Starter #7
Yes that is correct no shorts in wiring and 3 pins on each connector are showing continuity as they are supposed to
 

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Discussion Starter #9
I might try checking continuity again but this time moving the harness. Maybe there is a partial break in wiring and it’s intermittent?
 

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was thinking about this on way home....checked pinout numbers last night (shop manual) and OF course forgot to bring numbers with me, I am sure yours are correct......I thought well maybe the ECM ,but if that was the case (and I am not sure of its programmed logic) but if it was bad it (ECM) it probably would not recognize a low voltage/fault and throw a code.... make sense to you? As to measuring, see if to can rig up a like a small lamp 5 watts and test said wires in a series circuit to see if light bulb does indeed light up ,it is possible that you have continuity showing on your meter but wire is unable to carry the current that is drawn by the sensor..... definately a puzzler,hang in there
 

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Discussion Starter #11
I don’t think the ECM is bad since it’s throwing the code and it’s communicating with vag tool and showing voltages.

I’ll see what I can find but I may have to stop at a hardware store. Shouldn’t be too difficult.
 

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Discussion Starter #14
If the picture isnt clear I have the circuit run like this.

12v battery positive > wiring harness > 5w bulb > 12v battery negative

I figured that would be the best way to test. If the harness is bad the bulb wouldn’t light up or might be dim.
 

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Discussion Starter #15
So ended up replacing the knock sensor again. Made sure to clean up the engine surface again just to be sure. Still same problem. Only getting .23v on cyl 1/2.

I unbolt the sensor from the engine and I’m still getting .23v

Bolt it back on and I get a small response around .23 - .49v

Am I just not torquing the sensor enough?

I’ve been going off 20nm / 14.75 ft/lbs for torque. I’ve been using a smaller torque stick that is measures in/lbs and torquing the bolt to 177 in/lbs
 

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ugh..... that was quick.......positive (12 volt) to bonnet (knock sensor plug) thru the harness to brown wire (pinned out to ECM connector) to bulb, thru bulb to black wire to ground, makes perfect sense and confirmed on all three of sensors wires.... wow ,great job ! but still no answers.......long ride home for me and digest, hang in there.........
 

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Is there any chance the wires are long enough to swap the connectors between the two knock sensors? That would positively determine if it's ECM or sensor.
 

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Discussion Starter #20
Not sure what you mean by that. You mean swap the sensors around? That’s not an option sense the connectors are slotted differently. I do have a spare bank 2 sensor and I could also unplug sensor 2 to see if sensor 1 responds differently. The only way to swap sensors would be to make jumpers and and cross the wiring at the connectors.
 
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