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UK Car Repair/Opel Astra 1995



I have Astra F with C18XEL engine. There is trouble code for the knocking sensor and as I started to investigate, I noticed the wire from the sensor isn't plugged in to anything?? I have searched literally everywhere, countless hours with no success. What on earth should I do with it? There is nothing that helps on repair manuals or internet.

I consider wiring it myself directly to ECU or something...if I only knew where the wires are supposed to go :)

ANSWER: you have the wire FROM the sensor, and cant find the loom to plug it into?

Look behind the engine in the gap between bulkhead/engine with a torch, the wire might be dangling back there, or tucked near the intake/underneath the intake duct/manifold.

If you cant find the sensor itself, its on the back (intake side) of the engine, down on one side of the crankshaft.

I did the headgasket on one of these engines and never saw the knock sensor or its wiring. Its going to be right in the depths, on the back, in the corner. Horrible engine to work on, rough castings - wear gloves. possible location

this page and site should help

this site probably will help

You should be able to handle it. Ecu wiring is probably on that third site too.

---------- FOLLOW-UP ----------


Thank you for your response! I know the location of the sensor itself, the correct part of the wiring harness to plug it in is lost!

I have already removed the whole intake manifold to gain better access between firewall and engine with no success. I think I have followed every single wire in there! And even there is not that much wiring in such an old car, it has been a real pain in the know if you did work with one of these :) doesn't have the necessary pictures available, already checked from there several times. Why is that those exploded view- and component location pictures are so damn top-secret? One of the links you gave me had the wire I'm looking for in it, but didn't show enough :(

Sorry for late reply my email is a mess.

One check - if this isn't the original engine, the knock wire might have been ripped off in the swap process, then had the loom tape wrapped over the exposed pieces.. its more common than I'd like.
One last uninvasive method.

'Chop the ecu loom up and fix it' :o)

Pinouts on the ecu and the pinout of the sensor, probably has grounded body, input, and signal out. 3 'wire' sensor really. early ones were single wire..

pin 1-2 knock sensor ---> pin 1-20 ECU  

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Christian Boyce


Extensive knowledge of cars designed between 1900 and 2000. I have an interest in keeping these early cars on the road - I love the classics and want to keep them around. I'M BACK!. A LOT of reasonably classic cars are going TO SCRAP with no good reason. I want to stop that. If it's cool and you're having trouble with it, just ask. Also I'm looking for a job. I can do bodywork too. Not welding yet. Everything else and more though.


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