Check Engine - Knock Sensor :(

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Check Engine - Knock Sensor :(

Post by Sonac » 21/04/19 21:38

So for the past couple days my engine has been running lean. I only drove it twice like this out of necessity and I went super easy and never hit boost, monitored the coolant temp etc. No issues.

Turns out it was just the o2 sensor wire that was shot. I replaced it and the car is running smooth on 14.7 according to my wideband. Cold start is low 13's and warm idle is 14.7-15.0 so bang on really.

Only problem is while the car was running lean the check engine light came on, I read the code as 52 which is knock sensor. Makes sense since I was lean. Now I can't get the engine code to go away.

I followed the guide on this website which said remove the EFI fuse for more than 10 seconds. I left it out for a good 30 seconds. But as soon as I start the engine and rev over 2.5k rpm the check engine light comes back. Always at 2.5k rpm.

I'm really confused as to what is causing this as my AFR is perfect now.

I'm leaving the EFI fuse out over night. I hope in the morning its fixed. If anyone has experience with this please let me know! Thanks



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Re: Check Engine - Knock Sensor :(

Post by jimi » 21/04/19 22:14

Perhaps your knock sensor is faulty, it's not unknown for knock to kill the sensor. There's a chance that running with a faulty O2 sensor, caused enough knock to kill the knock sensor ?
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Re: Check Engine - Knock Sensor :(

Post by Sonac » 21/04/19 22:38

After reading the stories on here about the knock sensor it seems you are probably right about it being broken, other people also stated that knock can kill these sensors. They are really expensive new though. Found a second hand one in working condition cheap though from a breaker. I'll probably grab that.

Seems a bit stupid that a knock sensors breaks after if detects knock though. Thats like designing a check engine light to break after it comes on once. Only a check engine bulb doesn't cost over £100.

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Re: Check Engine - Knock Sensor :(

Post by MR2DI4 » 21/04/19 22:51

These cars are now so old anything can fail. Heat and time along with vibration just degrade things. The piezo electric element is pretty fragile and its not really designed to work for a long period if your engine is experiencing knock. I would say that the sensors now pretty much fail straight away if they suddenly experience a condition bad enough required to throw an engine check light due to knock.I mean if you start hitting anything with a hammer made of crystal its going to break sooner or later.

Wouldn't waste my time with a used one, there are plenty on E-Bay that are new.

The main thing is to fix the problem with the fueling first, then chances are you will never have to worry about it again.

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Re: Check Engine - Knock Sensor :(

Post by Sonac » 22/04/19 15:25

MR2DI4 wrote:
21/04/19 22:51
These cars are now so old anything can fail. Heat and time along with vibration just degrade things. The piezo electric element is pretty fragile and its not really designed to work for a long period if your engine is experiencing knock. I would say that the sensors now pretty much fail straight away if they suddenly experience a condition bad enough required to throw an engine check light due to knock.I mean if you start hitting anything with a hammer made of crystal its going to break sooner or later.

Wouldn't waste my time with a used one, there are plenty on E-Bay that are new.

The main thing is to fix the problem with the fueling first, then chances are you will never have to worry about it again.
Yeah the fueling issue is already fixed. Its no longer running lean. I said in my original post it was just a bad wire from the o2 sensor which I have replaced. Runs really well now (other than being in limp mode). I did end up buying a sensor used since it was £25 rather than over £120 new and I don't trust those £20 Chinese ones to work. Its listed as used buy in fully working order so If I install it and the check engine light comes back then i'll just get my refund.

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Re: Check Engine - Knock Sensor :(

Post by jimi » 22/04/19 17:28

:th: Keep us updated on your progress
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Re: Check Engine - Knock Sensor :(

Post by BALDYMONSTER » 09/09/19 19:00

I’m having the same nightmare with my engine management light coming on due to fault code 52. Knock sensor signal.

I tried an eBay special at £27 but that just caused the light to come on straight away as opposed to after 30 mins driving with the original.

Bought a second hand genuine Toyota knock sensor and tried that, management light on straight away again!

So I put the original sensor back on and I’m getting the management light on as soon as I go near 2000 rpm.

Engine is tight as a drum, compression fine on all cylinders, no smoke on start up, or idle, or under acceleration or on the overrun.

The car doesn’t use a drop of oil either.

Always run on V-Power and oil and filter every 3000 miles.

Any ideas on what to try next? Or what to look for?

Or should I drop my scants and go to Toyota and get dry bummed for a new Toyota sensor?

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Re: Check Engine - Knock Sensor :(

Post by Sonac » 11/09/19 11:10

Are you sure you aren't getting knock? Do you have an AFR gauge installed? My car didn't sound like it was knocking at all even though it was due to the dodgy o2 sensor. My AFR showed I was running lean though.

These sensors are super fragile and blow really easy under knock condition. I heard another story when I was frantically googling when I had my issue. Pretty much same as yours. They guy just kept getting bad sensors. He eventually lucked out and got a good one.

Else the only thing I can think of is some kind of wiring issue between the knock sensor and the ECU.

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Re: Check Engine - Knock Sensor :(

Post by BALDYMONSTER » 11/09/19 14:31

I know mate, I’ve just removed the ECU and had a good look to see if anything is blown but all looks ok.

Wires are all tightly in place in the multiblocks, next thing is to run a new wire and if that doesn’t sort it then it’s a brand new Toyota knock sensor.

I’ve had a second hand Toyota one and a cheap eBay number but both made the management light come on and stay on from start.

If the car is left for an hour odds it will run fine with no management light on for about 20-30 mins.

Probably a wiring issue as I had to reroute all the wiring and insulate it after the infamous specialists conversion. Lol.

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Re: Check Engine - Knock Sensor :(

Post by jimGTS » 12/09/19 13:09

Sonac wrote:
21/04/19 22:38

Seems a bit stupid that a knock sensors breaks after if detects knock though. Thats like designing a check engine light to break after it comes on once. Only a check engine bulb doesn't cost over £100.

the sensor has constantly been detecting knock clearly and its eventually blown from a large knock event. by blowing its now protecting your engine from any sort of load/boost/revs.
with a blown sensor the ECU is locking you into limp mode until you replace it (and blow it again if you dont fix the original reason for it blowing, ie bad fuel, too much boost, bad ignition creating knock/det).

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