EGT Sensor and CEL
 

Hello,

My 01 WRX bugeye is due for an MOT in the next couple of weeks, and when I had the car serviced last month, the garage reported that my car was blowing from the up pipe. Last week I had the up pipe replaced with a decat one, but unfortunately the garage could not remove the EGT (exhaust Gas Temperature) sensor without damaging it. Apparently the end was melted off anyway...

So now I have a de cat up pipe with a bung in the EGT sensor hole and my EGT sensor is floating around my engine bay. I was told that leaving it connected would prevent the CEL from coming on, but that didn't work!

I now have an illuminated CEL and the car acts like its freezing cold every time I start her up. How essential is the EGT sensor? I have read on the web that I can replace it with a 2k2 Resistor and this will switch off the CEL. Has anyone done this? Can someone explain the reason why the car needs an EGT sensor anyway? I can understand oxygen/lamda sensors and so on but why is exhaust gas temperature so important? And if it is so important, would that mean its better to replace it with a working sensor than with a resistor?

Any answers to these question swill be greatly appreciated! :D

The EGT sensor on the WRX was fitted to protect the up-pipe cat.
If (for whatever reason) high EGTs happened then the cat could melt or break up. If the cat breaks up then it would lunch the turbo.

With your decat up-pipe there is no real need for the EGT sensor, although some would fit a different type on big power builds.

Remove the EGT sensor at the plug on drivers side suspension turret and plug the resistor into the socket. Cover up socket to stop water getting in.

This should prevent a CEL causing an MOT failure.


Nick

Could a CEL cause an MOT failure? :eek:

AFAIK it's not a "fail" as such as mine recently passed it's MOT with an illuminated CEL. I told the garage that it was the missing EGT sensor and the resistor fix playing up (which was the truth) :D

Either CEL fix as Butty mentioned or buy a new EGT sensor :D

Shaun

Well I went to maplins today and handed over my hard earned 15p for a 2k2 resistor.

When I was at school, I'm sure that the colour code for 2k2 is red red red. The Resistor that I've got isn't red red red. The guy tested it in the shop and it came out at 2200 ohms (but I'm not sure if I trust him...).

Anyway, I jammed the resistor into the socket by the drivers side suspension strut and it didn't fix the problem.

Methinks I'll be testing it with my own multimeter this evening... it could also be that in my haste to fit the resistor I didn't get good contact with the pins in the socket. I examined my old EGT sensor and I can see where it is damaged. So I decided to cut the connector off. I can now solder the resistor to the connector and at least have it looking semi respectable (as long as I can prove that the resistor is really a 2.2k ohm resistor).

Watch this space...

It will take around 5 ignition resets to see the resistor as far
as i can remember before the CEL goes out, it wont work straight away 1st time.

Is that five warm up/cool down cycles, or 5 ignition on/offs? :)

yeah should take a few starts to get it off, mine took a few more than 5 and it came back once, just make sure its wedged in good.
just start and stop the car a few times, no need to drive dont think.
I have 9 left after doing mine, cud only get a pack of 10. so if you need one let me know.
The ecu reads it as about 680 odd degrees with the one i have in.

I measured it on my multimeter and checked the colour codes on the interweb and I'm fairly sure its a 2k2 resistor. I didn't like the idea of leaving the connector open to the elements even with a bit of tape so I decided to solder the resistor to the connector from the original EGT sensor. I cut the wires on the EGT sensor and then stripped them ready to solder. Spend ages trying to solder the *******, but the wires are made of some kind of sprung steel and the only solder I could find was flipping lead free crap. In the end, I got some crimp on spade connectors... cut the spades off and crimped the resistor onto the ends of the wires using a vice. With a bit of shrink wrap over the resistor and the connectors, I tested the resistance again to make sure.

I plugged the connector back in, and started the car. Still a CEL. Stopped the engine and restarted it and no CEL! :luxhello: :lol1: :p

I've been having problems with my resistor mod this week. Car was remapped at the weekend and it discovered that my sensor (uppipe) was faulty, so on monday went to dealer, got bolt in uppipe to blank off and a resistor was soldered in, ecu reset all good. today, CEL comes back on :mad:

I'm thinking I may have used the wrong resistor, got mine from maplins, the body of it is light blue if that helps,

or the resistor may have blown if so how can you tell - checked it earlier and it looks ok, tried starting and stopping the car 5/6 times didn't work, tried disconnecting the battery for 10 mins also didn't work ...

any tips?? this light is driving me nuts!!

I've given up and I drive with the EGT CEL on all the time........ The ECU is supposed to monitor the EGT and expect a variable signal, Sometimes the ECU sees the static signal generated by the resistor as a fault and throws the CEL :)

I might swap the resistor again when the weather gets better and I won't get wet LOL

Shaun

just been to garage and they have cleared the CEL. Lets see how long this lasts for ....

question - is it possible to put the resistor in the wrong way round?

i'll be doing this shortly as well as putting a STI uppipe on my '02 WRX (current uppipe is blowing badly).

Does anyone know exactly which resistor is needed? I know its 2.2k Ohm, but they have different watt ratings. Or does this not matter?

cheers :)

you need 1/4 watt

Or greater.

Its very hard to get resistors that do less than 1/4 of a watt, and that would be the only situation in which they would 'blow'. If a resistor 'blew' then it would go big style and would probably turn black and charred. I personally have never seen a 'blown' resistor. They are effectively just a coil of wire designed to conduct electricity but convert some of it to heat.

You cannot get a resistor the wrong way around as they have no polarity.

It is more likely that the resistor has poor contact with the connector in front of the front suspension which is why I crimped mine onto the wires connected to the existing EGT connector rather than just plugging it into the socket. The socket is obviously designed to take the flat blades on the EGT sensor and NOT the bare wires of the resistor. I bet that the issue is with an intermittent connection rather than anything wrong with the resistor itself.

thanks Marjay, so far since the garage reset on Friday so good. The code that came up was something like unknown error .. 39**** or something similar. Now that the ECU has thrown this code/error and has been reset, does that mean that it wont throw the light again for the same reason, unless the resistor connection does break or blow etc?

on my way to work this morning I was thinking of coming on here and posting so far so good, a weeks motoring CEL free, then, as if my car know I was thinking about it PING and on it came aaaahhhhhhhhhhh time for the black tape I think