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tdi power
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Discussion Starter #1
how does the knock sensor's wire connect to the ecu? does the wire go straight to the ecu from the sensor or does it go to something else first?
 

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AKA RSP
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There is a multiplug on the left side of the engine as you look at it near the top rad hose outlet. The knock sensor wires look like speaker wire in that they are clear and you can see the wire.

Richard
 

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tdi power
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Discussion Starter #6
could i then just run a wire straight from the sensor to the ecu to see if there is a problem with the wire's and if i do does it matter which one i connect to which wire?
 

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technically yes BUT i dont know what else is also connected to the multiplug on a GTS (or GTR for that matter) as to correctly test you would need the knock sensors only connected to the ECU inputs (pin 23 & 24 from memory).
 

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tdi power
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Discussion Starter #8
i will leave the multiplug connected just run another wire from the sensors to see if this helps.
 

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how are you gonna do that? theres only one wire that connects to each knock sensor, you gonna cut the wire at the sensor end or something?

What are you actually trying to achieve? do you believe you have a faulty sensor or something?
 

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AKA RSP
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If there was a break in the original wiring it would have a fault code logged in the ECU as it will not be seeing a signal! I expect running a new wire would do nothing. The sensors can go faulty without causing a fault code as they still send out a feed to the ecu.

Richard
 

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Yes, the upper of the two clear wires at the multiplug goes to 23, the lower to 24. I have just run a wire shoved into the plug round and in through the passenger door to the ecu to check continuity through these wires. By the way it is much easier to stick a pin in the back of the plug to check resistance/voltages than to remove plug from ecu. Also you can check at ecu with ignition on/ engine running if needed in this way.
 

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Don`t mean to hijack but it sounds as if you may be checking something similar to me. I`m trying to work out why I`m getting 0.5 volts at pins 23 and 24 rather than the 4 volts it states in the workshop manual, as I would expect one or the other of the knock sensors to go wrong rather than both so was suspecting a power supply issue but if the sensors only have one wire, how do they get power? They must have at least one more wire for power supply if they earth into the block or more likely two power and earth.
 

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AKA RSP
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The sensor earths out to the block and the sensor changes the resistance of the wire to the ECU.

What problems are you having to think its knock sensor(s)?

Richard
 

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tdi power
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Discussion Starter #15
mine is all sorted now thanks to rich and his team.
 

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The sensor earths out to the block and the sensor changes the resistance of the wire to the ECU.

What problems are you having to think its knock sensor(s)?

Richard
Cool, thanks, one wire it is. Been reading up on all this piezo electronic stuff, clever how they work.
Seems like its the usual problem from reading this board, 200 miles from full tank, stalling when coming off throttle on occasion, hesitation when you accelerate a bit, suspected lambda sensor, but this checked out O.K. after finally downloading a workshop manual that works on my pc, so I did the rest of the checks it suggests which are easy, throttle position, temp sensor, afm, knock sensors, everything was exactly as the manual says except knock sensors, which both read a way low voltage from ecu, so first was check wire from ecu to sensor and was fine. now I don`t know what to do as I`d rather not take the inlet manifold off to get at them. lambda sensor would have been easier to reach.:thumbsdown:
 

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What does the workshop manual say to do? what do you experience?
 

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r33 manual, section EN7 in contents "Fault diagnosis by self diagnosis system", pages EN 312 -> EN 315.
Fault number 7, detonation sensor system (fault code 34) page EN 322.

section C input signal to ecu inspection.
It says measure the voltage between pin 23 and earth and pin 24 and earth. You should read 4v when ignition on, 4v when cranking, and 4v when engine running. Now I admit I havent checked it when cranking as this means pulling plugs out AGAIN, fuel pump fuse out, etc. cant be arsed. but for both ignition on and for engine running I am reading about half a volt from both pin 23 and 24. The manual says replace sensor but I`m surprised that both have gone. thats why I suspected a dodgy wire or dry solder somewhere. but the sensors are on a separate wire from each other. I have checked both wires by joining a wire temporarily at the multi plug near the front of the engine and running it back round through the passenger door and got good continuity from the ecu through the loom to the plug and all the way round back through the door so the wires are good. This leaves the ecu or the sensors or the short bit of wire from the plug to the sensor. Personally I`m thinkink the sensors have gone. I am getting code 55 from ecu (no fault) but I have read that the ecu will give a fault if the sensors give wildly different readings from each other but they both give the same (wrong) reading. I think the ecu believes their reading and thinks there is a problem with the running so retards ignition/increases fueling.
 

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Ok fine just wasnt aware of the 'correct' procedure, there is another way to test your knock sensors too if your really keen (like I was). Its a bit of a pain to explain quickly but basically you need to connect your knock sensors to an amplifiers input (like an old tape players mic in or similar) then tap the head or block with a screwdriver. You should hear everything nice and clear. I have example recordings if your interested to hear what it should sound like :)
 
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