Det sensor

I know this is a Bain of the gtir world but is the first time I've had this issue.

The new gtir project I have bought throws up code 34 - det sensor. I have serviced it including an ignition service.

Symptoms I have is the power is just not linear at all, it stumbles as it builds up boost, but after 5000rpm it flies. Is this a symptom?

The code 34 - is this showing a knock sensor FAULT? Or the ecu recording that is is detecting det? I'm presuming its more likely a fault sensor. My next question is can I temporarily by pass it.... I.e. unbolt it from the block and wrap it up I've heard? Add a resistor in the wiring?



For your info, the only mods are an old apexi afc, I have no idea how well setup - and the usual bits like exhaust and filter. The car runs ok, and drives ok but the delivery of power and the drive up through the gears as it wants to make boost it starts to hold back and as it breaches over 4/5k it the pulls great, almost like the boost is being switched on like a light switch,

Cheers guys.

First thing you want to do mate it's clear the code then drive the car again see if it reappears.

Yes that is a symptom.

You can bypass it. It wouldn't do your car no good.

I would advise is test the sensor with a multimeter you can back probe it at the connector and see what voltage you are getting


You should get 2.5 volts

Hope that helps mate

You get 5volts coming to the connector. When it's connected up to the sensor its 2.5v

Car was driven, code brought up and reset, then driven again and also code come up again and then reset again.

I know its hard to get to, easiest way to test. Or can I take it away from the block and wrap it in a rag to see if problem goes away?

Is absolute pain to get to. We'll depends if you have the y bracket there..  You wanna check your wiring harness is not broken. Or the sensor is not bolted down tight.  

Like i Said check the harness if 5 V is flowing through

No you can't put it around a rag. Because the back of the sensor is earthed to the block. Needs to detect pings from the engine which fluctuates.

If it does not detect any thing it will throw the fault up

Someone more senior can correct me if I'm wrong but as far as I know it's that

You need to remove it to ohms test it really
If 34 keeps reappearing it's more than likely the det sensor is knackered.
Remove it and test it and should be showing more than .556 mega ohms if less then you'll need a new one
As said it's not a good idea to do away with it as you'll have no safeguard if your engine dets which is a strong possibility if you have an antique afr unit

Im going to pull the AFC off tonight and revert it to stock.

My next question is, can i in anyway disconnect or unbolt that det sensor so I can do a test run on the car?

Oh sorry just read turbazz's comment, so wrapping up the sensor doesnt work?

I guess its test and replace with new if faulty then   

Just got a brand new knock sensor for £21 + vat from me work so for that sort of money i might aswell just bosch a new one on

No it won't work if you wrap it. Needs to pick up frequency off your engine. The back of the sensor needs to be earthed too. When you bolt it down it makes contact with the block

Put the ignition on not engine..
The harness you should get 5 V..
You don't your wiring is damaged.

Then if you connect the wiring to the sensor squash two wires in the clip.. And then measure the back voltage it should be 2.5 V..

I did this few weeks ago. It is very fiddly.
I got the voltage figures of a guide on the Internet.. When testing mine it was correct!

Does anyone know the torque setting of the det sensor? I know its got to be very precise....

test the new one with ohms meter before you fit it ross
don't know where you got it from but many of the cheap ones have a smaller reading and wont work
ideally it should read .558 or more

Mine is showing det code fault but it's running really nice. I have the y bracket on. Should I leave it till I get the engine out over Christmas or change it from underneath??

leave it if not bothering you Darren
replace it once you have ditched the Y bracket

That's just what I wanted to hear, even better when it comes from you. Bill came round for me to swap his over. Managed to get a socket on it but monkey arms Dave had done it up so tight I couldn't get it off, so looks to me like exhaust off and oil filter to create more working room and go from underneath.

Can anyone confirm whether or not the det sensor can make a difference at idle?

Bones wrote:That's just what I wanted to hear, even better when it comes from you. Bill came round for me to swap his over. Managed to get a socket on it but monkey arms Dave had done it up so tight I couldn't get it off, so looks to me like exhaust off and oil filter to create more working room and go from underneath.

take the startermotor out and you can get to it from there with that out the way, easier than doing it from underneath



ross...........det sensor wont cause idle issues

GTI-R US wrote:leave it if not bothering you Darren
replace it once you have ditched the Y bracket

Out of curiosity I have a code 34 but the car seems to run perfectly. Also on my last Gtir the sensor was physically cracked and the car still ran fine.

I have a good sensor to replace mine when I get round to it but I'm curious as to whether it still does its job even though its throwing a code, at what point does it become a problem and badly alter how the car drives? I don't have any particular fear of det as the ecu will likely be mapped rich.

MOT tester did remark that it was running rich on emissions though so unsure if that is the map or the faulty sensor causing that.

Have you cleared the code and its come back ????

Yes comes back immediately. Cleared it about 5 times so something is iffy but not noticeably affecting the car.

Could just be on its last legs and not quite putting enough volts or slighty iregular wich is throwing up the code but not causing an issue as of yet .... have you tried ohm testing it ???

Not yet, I've not had it off, and my unit is occupied by a mates clio at the moment so going to wait until after it's out to do it, have got 2 spares that I have ohm tested and are fine.

I was just curious as some people seem to have huge running issues with iffy sensors.

Yeah i always thought it cuts power ie safe mode or holding back at higher revs obviously detecting det or so called det ...

As I understand it retards timing if it detects det but should go into limp mode or light the check engine light if the sensor is completely duff.

It can't cut boost unless you are using the standard boost solenoid so on a modified car it would just richen the mixture and retard the timing, unless of course the aftermarket or modified ecu reacts differently.

Perhaps performance has been affected from the start and I just haven't realised, hard to know what a 350+hp gtir should be like when I have nothing to compare it to.

Yeah it does retard the timing ..... it should feel quite quick depends on how many you have owned of course ... but soon get use to the power anyhow ...