Lude Generation

Hi all, I currently have the CEL engine code 23 which referes to a knock sensor problem. Can anyone advise on the correct replacement knock sensor as I've spent most of today trying to find out with no conclusion? The engine type number is in the format H22A-4000xxx. Any help much appreciated! Best regards, Batsy

Any h22 knock sensor will work. However....
On a Type S it's above the atts unit. It's an atts off job just to get to it. A good 10 hours labour just to change.

Could you not take the inlet manifold off instead to get at it?

Vtecmec wrote:Could you not take the inlet manifold off instead to get at it?

Tight but yes. Probably easier.

You don't have to do either and id advise against them as both will be a major headache and you'll probably break something, i managed to replace mine without removing the ATTS or inlet manifold, but if you are doing it on your own the procedure requires really skinny arms and some acrobatics/contortionist skills I spent days researching this and after a while i found a single post that mentions its possible and gave a vague idea of how to do it, over the course of a few days and some trial and error i figured it out.

You'll need a deep 24mm socket on a 3/8ths drive ratchet and long extension and u-joint, I didn't document this when i did it as its a pig to do but ill try to explain...

First make a bit of room by removing the airbox and induction hose.

Next you need to disconnect the knock sensor, from the driver side of the bay there is a gap under the inlet mani just below the egr valve, squeeze your hand in there and you should be able to reach in and disconnect the sensor. Its drokking tight and your forearm will be in pain but its totally possible.

Next you need to disconnect the vacuum box under the inlet mani and remove it, this part is done blind once you are familiar with where all of the hoses, connectors and bolts are.

Undo the bolts that hold the harness in place under the inlet mani, this will allow you to pull it down a bit, with this out of the way you can slide a deep socket with a u-joint and extension in from behind the inlet mani. The tricky part is lining the socket up with the sensor, you have to lie over the engine bay with your right hand on the end of the ratchet guiding it in, then at the same time slide your left hand in under the inlet mani in the same way you disconnected the sensor, while you push at the ratchet end with your right hand you can guide the socket onto the sensor with the left hand, this requires a lot of jiggling with both hands but it will go on. Now its on there you can undo it, try not to drop it on the way out...

Now put the new sensor in using the above technique, this is even trickier as its really difficult to line the new sensor up and start screwing it in, make sure you torque it to spec and the rest is just the reverse of the above. Almost as difficult as changing the sensor is reinstalling the vacuum box blind

Oh what fun the Type S is

That took longer to write than expected, oh well at least its out there, hope it helps someone.

That's certainly easier than the other options.

if its such a ball ache to remove - i would advise some checking before hand to rule out that the sensor is in fact part of the problem.

EG, see code - assume sensor, get distracted about how hard it is to remove, lose sight of original issue.

If i had this code - id check continuity at the ECU end first, and also check what circumstances the error is thrown, in case its indicating a real symptom (rather than just sensor failure). The official manual might shed light on the true meaning of the code?

I might be imagining it, but i think you can listen in to the sensor output as they are effectively tuned microphones designed to pick up on certain vibrations/frequencies?

Eitherway - glad i'm not having to replace mine (Atts or otherwise)

Hi all, it's been a while! Just wanted to resurrect this ancient thread to say thanks @Max for the inspiration to replace my Type S knock sensor without removing the intake mani or ATTS - and to anyone else stumbling on this issue, it’s 100% possible! I used a different method and found it okay to do, just requiring a lot of patience and a steady hand.

Most importantly though, step zero - check there isn’t a wiring problem. Geeky stuff ahead...

Yes, @Scott560 you're right, the KS is just a piezo microphone like you’d find in an electro-acoustic guitar! You can backprobe it from the ECU end (pinouts in the helms) by plugging it into an unbalanced instrument input.

You’ll need to find a laptop, buss-powered USB audio interface (get an old Scarlett Solo from eBay), a 1/4” jack cable and some test leads with croc clips and a pin. Just connect a lead to the tip and another to the ring of the jack cable, the other end of one lead to chassis ground and the other via the pin into the back of the ECU connector (pinouts are in the helms). Plug the other end into the audio interface’s instrument input.

(I had a heart stopping moment where I thought I’d connected my ECU to a +48V phantom powered mic input. Don’t do that.)

Note that there's no need to turn on the ignition as the sensor is passive, so maybe disconnect the battery first.

Fire up your laptop and audio workstation of choice (I use Reaper, it’s weird but fab) and record yourself drumming on the block. You should see a waveform and be able to listen back and hear the knocking. If there's nothing there then there's a wiring problem, good luck with that. If you like, now’s the time to get a cheapo eBay KS and compare the two.

(I found that the sensor on the car was functional, but had much weaker low frequency response than the eBay one. Upon removal my sensor fell apart - so take note that although there might be a signal present, it can still be bad. There’s folks on YouTube using a multimeter in hold mode to demonstrate a signal but that doesn’t prove the sensor is good.)

So, given that you’ve proven that there’s not an open or short on the line, you’re going to replace that sensor. I used the eBay one as I wasn’t confident the sensor was the root cause, but it turned out to solve it! I will see how it lasts, but I’d be happy to do this process again if the eBay sensor fails - might go with OEM if that happens, though they’re hard to find and cost ~£200.

Just take a moment to play Operation or one of those grabby claw fairground games to prepare yourself for the frustration…

1. Get hold of one of those endoscope camera kits off Amazon for like £25 - they’re amazing. I have no idea how you managed to do this by feel alone, this makes it massively easier to know what’s going on under there once you get used to orienting the thing.

2. Using the camera, find the bolts to remove the IAB tank and gubbins and various bolts on either side to loosen the plastic loom cover (I have no heater core or pipework, so that might need to come out too, IDK.)

3. Get in there with the camera and some extra long nose pliers to remove the KS connector (I was terrified it’d break but it came off surprisingly easily)

4. …then remove the sensor with a 24mm deep socket and extension. Fiddly again but doable.

5. Replace sensor using some blu-tac in your socket to stop it falling out on insertion, torque it to the spec on the KS troubleshooting page in the helms.

6. Get the damned connector back on, this is the worst part but it can be done with extreme patience! I tired taping the camera to the pliers which felt really neat but ultimately didn’t help. You just have to find some way to get the camera in a useful spot with one hand while using the pliers with the other. It WILL go on!

Now we’re done! Plug the gubbins back in, start it up, run up to temp and hold the engine between 3 & 4k while performing your luck ritual of choice.

Yikes that was long, guess it makes up for no posts for the last decade or so

Glad to see my tinkering finally helped someone