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Knock sensor help code 52


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Re wired my knock sensor have full continuity have put in a brand new knock sensor and still get code 52 , resetting the ecu now (jam ecu) to see if that clears the code but if not what then , ecu fucked ?

Edited by Dean_mc88
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Right so turn my car over all sound , rev over 2k and the engine management light comes on code 52 knock sensor ,

drive it and it feels sluggish under full throttle however 10% throttle revs brilliantly all the way round.

If I plant my foot in 2nd gear onwards after 5k revs the car jerks and misfires and loses power I've checked continuity and put in a brand new knock sensor all perfect now any suggestions

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  • 1 year later...

Also, AFRs are around 10 or lower, so rich... I presume the ecu thinks there is knock so making it run rich, but see no reason for there to actually be knock. Running the same map it's had for over a year and nothing changed apart from a head skim which I've been running since for a while.

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I've fixed alot of these and from my experience the causes are:


(in order of likelihood)



1- Break in wire or damaged wire causing no connectivity or abnormal resistance readings from end to end



2- (Related to the repair of above) Incorrectly joined shielding around the signal wire.


Either earth shield connected at the knock sensor end (it shouldn't be)


Or the earth shield not rejoined from break point (usually by injectors) and the wire picking up inductive electrical noise (alternator etc)



3 - Knock sensor plug wire end terminal not clamping the knock sensor terminal correctly causing a poor connection


De-pin, clean and tighten



4 - The knock sensor is faulty and needs replacing.


I've only seen this half a dozen times in the last 10 years.



Re AFR's and running like a bag of dicks - yep I'm certain the ecu pulls a chunk of timing out when it falsely detects knock (this is generally what happens with aftermarket ecu's) and possibly throws some more fuel in to slow the flame front although im guessing on the last part.



For the poster above, skimming the head will raise the compression and dependant on how close to peak timing your original tune was it may cause some knock? Bit hard to gauge without knowing what ecu your using and the state of tune etc. You could try to knock a few degrees of timing out of the whole map and see what happens?



Hope this helps


Edited by Stu
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I've fixed alot of these and from my experience the causes are:

(in order of likelihood)

1- Break in wire or damaged wire causing no connectivity or abnormal resistance readings from end to end

2- (Related to the repair of above) Incorrectly joined shielding around the signal wire.

Either earth shield connected at the knock sensor end (it shouldn't be)

Or the earth shield not rejoined from break point (usually by injectors) and the wire picking up inductive electrical noise (alternator etc)

3 - Knock sensor plug wire end terminal not clamping the knock sensor terminal correctly causing a poor connection

De-pin, clean and tighten

4 - The knock sensor is faulty and needs replacing.

I've only seen this half a dozen times in the last 10 years.

Re AFR's and running like a bag of dicks - yep I'm certain the ecu pulls a chunk of timing out when it falsely detects knock (this is generally what happens with aftermarket ecu's) and possibly throws some more fuel in to slow the flame front although im guessing on the last part.

For the poster above, skimming the head will raise the compression and dependant on how close to peak timing your original tune was it may cause some knock? Bit hard to gauge without knowing what ecu your using and the state of tune etc. You could try to knock a few degrees of timing out of the whole map and see what happens?

Hope this helps

Thanks for the detailed reply! I'm confident that the head skim wouldn't causes enough difference in compression to cause a problem. I could be wrong, but I have ran the car for a while since putting it all back together without any issues. I have a feeling it's more than likely going to be a broken wire after disturbing it.

I'll check it all out and report back :)!

Cheers mate.

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i had this problem for ages checked wires and all sorts bought a new sensor still didnt work then borrowed an ecu didnt help borrowed a sensor and turns out the new sensor i bought wasnt an oem one it was just shite. so picked up a new oem one and problem solved since


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Oh, another thing to remember is the knock sensors do actually work so consider things like the octane of the fuel your running, the boost level, base timing and the possible air intake temps. All of those have considerable effect on inducing knock


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All fuel, boost, timing etc are the same. I've checked the continuity and it's fine all the way from the plug to the Ecu. I tried unscrewing it and clamped it to the inlet so that it had a vibration, to check if it was actually detecting a knock but it's exactly the same. Soooo I'm hoping it's the sensor, which I'm going to change tomorrow.

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