EVAP and o2 heater circuit? Advice please!

[muffdan]

Hi Guys,

Been a silent member for the last 2 years and got a LOT of good advise and info from this site. It's awesome. I'm hoping you can give me some insight into my present problem which no-one else has seemed to come across and posted about yet.

I think I have a problem with my EVAP, not quite sure what it is, or what it does, other than create/maintain fuel vacuum?

My pre-cats went on me a week ago. While I was taking it to the garage, I also developed a slight rattle (sounds like pinking). MrT botched the repair  s:shock: :shock: s:shock:  by cross-threading one of the o2 sensors in the new manifold making it leak/useless at higher revs (wouldn't do more than 90mph in 5th)! I took this as a sign and bought myself a header off Che, fitting it myself with 2 new universal o2 sensors (from  w www.gendan.co.uk w ). Everything seemed fine, except the engine check light was on, and the rattle was still there when accelerating. I decided it keep driving as power was more or less fine (I have a uni-chip and thought it might need remapping to fully restore the power) and after some testing with a multimeter, discovered that the o2 heaters had a far lower resistance to the two I took off. However, the rattle has now developed at 4k and above, and the power is crippled. I decided to stop driving it, and get an ODBII reader. Now the reader has picked up 4 error codes, 2 I can understand and was kind of expecting, and 2 I don't:

P0443 - Evaporative Emission Control System Purge Control Valve Circuit Malfunction.
P0135 - O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)
P0141 - O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)
P0155 - O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)

I only replaced the two o2 sensors in the manifold, so I don't know why I'm getting a problem with Bank 1 Sensor 2, after the main CAT. Also, P0443 is a mystery to me, after a little research, I figured out generally what it is, and after looking at another thread here, I discovered that it could rattle if it's faulty?

I'm hoping that this could be what's responsible for my rattle and power drop? I'm also hoping that this just happened to go wrong the day before I got my pre-cats replaced, and my engine is actually fine!

Could anyone give me some info on what the EVAP is, where it is, and how I can fix it? Is it expensive?   s:wink: :wink: s:wink:  

And could anyone give me some advice on what to do about my o2 sensor errors? I know they're working fine, they just have a lower resistance in the heater circuit to the toyota ones, but I don't want to drive around with my CEL on, not knowing when something else goes wrong. Also, any ideas why the post-cat sensor would be reading a circuit error two? I put the multimeter on that sensor's heater too, and it read as expected. I only replaced my o2 sensors btw because MrT destroyed the thread on one of them and I thought it better to replace them both rather than just the one.

Sorry for the length post, just wanted to be thorough with the info I gave.

[GSB]

Never mind the evap unit. it sounds to me like your engine is already toast...

[muffdan]

I fear it might be, but having already paid for an engine rebuild because of pre-cat failure 14 months ago, I am very reluctant to continue my relationship with my car if I have to do it again   s:( s:(  

I'm hoping that this is an unrelated problem as the car ran well for 200 miles after (albeit with the CEL on since the Che's header and new o2 sensors). Might (probably) be clutching at straws here though.

Other than the slight rattle when the power was down, the engine seemed to run fine, I ruled out the rattle being pinking by using Optimax with an octane booster too! Made no difference. I was expecting to get a more 'serious' error code, something engine related but the EVAP is a stand alone component isn't it? If it's faulty, it might not be starving the engine of fuel maybe?

[Anonymous]

Never mind the evap unit. it sounds to me like your engine is already toast...

I agree with GSB here, your loss of power is probably caused by your main cat being blocked and the wrong o2 sensors may be what is causing your CEL's.

[muffdan]

Thanks guys, but you're really nailing me into depression here  s:D s:D   Here's a little more info though.

If I clear the error codes, the power returns which leads me to dismiss an exhaust blockage. I'd hope that MrT would have checked for that when they replaced the pre-cats.

Don't you think that these error codes are a little odd to be related to a damaged engine? The o2 sensor errors are in the heater circuits, which are errors with the actual sensors, not with what the sensors are reading, and as far as I can tell a P0443 is specific to the EVAP unit which is part of the fuel line and wouldn't be affected by a problem with the engine would it?

What I'd like to know is, is it possible that a damaged EVAP unit could rattle and could a P0443 cause the ECU to enter limp mode?

I just want to make sure I have a better understanding and idead of what the problem is before I take it to MrT to fix as MrT's philosophy is to randomly replace things vaguely related parts until the problem goes away. Very expensive.

[edward.carter]

If clearing the codes makes it run at normal power then definately sounds like its going into safe mode, however as for the reason, 'fraid I cannot be of more help

[kanujunkie]

firstly, what spec is your 2?
(jspec, european, UK etc etc. If UK spec, what about the 3rd o2 sensor)

secondly, after looking at the BGB, do you know if the PCV valve is working? for some reason that i'm not sure about it seams that a dodgy PCV will cause emission to play up. The BGB shows to disconnect the valve electrically and link it up to the battery to check out the valves operation, following that the only things you can do is change the 02 sensors and take it to Mr.T to put on there tester

[muffdan]

Hi,

Thanks for the info! It's an 00 UK spec. I changed the two o2 sensors in the manifold, and left the third alone. I did unplug it to measure the heater's electrical resistance to compare to the two new ones I fitted, and it was measuring about the same as the two toyota ones I replaced. The only reason I replaced the o2 sensors was because the thread on one had been destroyed by the MrT mechanic. As far as I'm aware the originals were working fine.

I have no idea about the PCV valve, and unfortunaltly I don't know what or where it is either! I don't know if it's relevant, but I unscrewed my petrol cap earlier and got no hiss. I always fill up, and I've done about 170 miles on the tank so far, so I expected to get a good hiss.

I've checked oil and it hasn't significantly used any, neither has the fuel ecconomy been bad. Fingers crossed this is something simple (simpler than an engine strip/rebuild anyway).

[kanujunkie]

the hiss bit is very relevant as your not pressurising the tank. The PCV valve is at the top of the engine bay and just to the left of the oil cap. It sits on a spiggot that clips into the air inlet manifold and has one pipe that crosses over the engine bay to the charcoal cannister and one the goes forward behind the engine to the throttle body

[markiii]

no, that is NOT the PCV that is the VSV 2 totally seperate systems

[kanujunkie]

no, that is NOT the PCV that is the VSV 2 totally seperate systems

sorry my mistake on terms  s:roll: :roll: s:roll:  , Marks right but i still mean the same valve

[muffdan]

cool, appreciate the info guys  s:) s:)  so it's the VSV that I want to tinker with, and that's the one to the left of the oil cap? I'll whip it off tomorrow morning and hit it with a battery and multimeter  s:) s:)  I'm guessing it (or a wiring break) is definitly at fault here as there's no tank pressure. Do you think this could explain the rattling?

I'm hoping that there is just the one fault, it's harder to believe that more than one thing's gone wrong at the same time.

As for my o2 sensors, I got the universal ones other people here have used from gendan, and they definitly seem to do their o2 reading job. I can't remember the figures off the top of my head, but the heaters register a resistance of about 0.2kohms compared to the 1.8kohms of my old ones. I'm guessing this considerable drop is below the ECU's fault threshold, triggering the CEL. Has anyone else had similar problems using universal o2 sensors? Although still doesn't explain the third sensor's heater circuit error  s:( s:(

[kanujunkie]

i've never heard of issues with the gendan ones so chances are your fine with them

[spit]

Yes they work fine. Stock resistance is just 14 Ohm, but I don't think the ECU is cute enough to register any fault other than an open circuit.

I had a brief and intermittent problem with a CEL after cobbling a resistor fix. Turned out it was down to poor soldering on my part  s:oops: :oops: s:oops:  

As for your 3rd O2 malfunction light, that is a mystery, but its not unknown for the heater circuit to break down under temperature and throw a CEL only to "repair" itself by the time you get the meter to it  s:roll: :roll: s:roll:  Usually a sign that its on the way out.

That said, for you to get all three codes together suggests to me that the wobble is somewhere else. It may in fact be something that clears with an ECU reset (not just a clearing of the code). I had an unreadable (J-Spec) CEL a few weeks back that appeared a few minutes into every journey, but since a reset - nothing! Alberto has also had some odd CELs indicating a single bank fault, even though his two banks are fed from a single signal source now  s:shock: :shock: s:shock:

So what am i saying? Not sure really.....but given what you're getting it might just be an ECU blip, or as you say a single fault that's registering as several.

Keep us posted.

[muffdan]

Hi Guys,

Sorry for the late follow up on this, broke my leg playing football and everything kinda got put on hold a little while.

I got my car to toyota this week and they said the fuse for the EVAP sensor had blown. They've replaced that and that's fixed all my problems! It's also fixed the bogus heat sensor circuit messages. I could swear I checked all the fuses in both boxes and they were all fine, they also said there was oil in it, which probably shorted something so maybe this fuse is actually with the EVAP, I don't know, or maybe I'm just an idiot and missed it   s:oops: :oops: s:oops:

[Anonymous]

Really glad you've sorted your problem mate, It's funny how it turns out to be something so simple and easy to fix, i hate it when people say your engine is knackered straight away.

Are all the 02 codes cleared now?

[Anonymous]

Mental. A simple fuse   s:oops: :oops: s:oops:  

Glad your sorted and your leg is ok?

[muffdan]

Yep, all o2 sensors reading fine, and the leg's not too bad now either! My engine is definitly louder now(since pre-cat failure), sounds more like a diesil sometimes at low revs but no CEL light, it's not using fluids and MrT seem to think it's ok so fingers crossed!

Now I can book my car in at SP to get my turbo!   s:D s:D

[spit]

Chuffed for you matey. Its a reality check for all of us to rule out the "simple" stuff before jumping in with any "toast" speculations!

I'm still confused about your O2 heater resistance readings, which you said were up in the kil-ohms. That was across the two (stock) black wires, yes? O2 heater resistance varies with temperature but I've never seen anything so high - 15ohm is a more likely figure.

Just a PS - O2 sensors don't like to have their resistance tested across the other two wires (signal and ground), although its safe to check the voltage on these with engine running...this is what signals the ECU as to whether they are reading lean or rich of stoich.

Academic though, cos you're CEL-free and pootling again. Nice one!

TTET? Even better!  s:wink: :wink: s:wink:

[muffdan]

I believe I measured across the two black wires, but it was quite a while ago and can't remember for sure..

For sure it's worth investigating the simple stuff, as it's not always a catastophy. I would never have thought a fuse could have caused all the symptoms I had!

My Silerstone Performance shopping list comprises of a TTE Turbo, the SP12 wheels, uprated clutch and TTE springs, TTE exhaust and some body pieces. Then a trip to Millway to get my Unichip remapped for the turbo.

I love my '2   s:D s:D

[spit]

Don't forget to have a look here if you're considering an uprated clutch  s:wink: :wink: s:wink:

[peppyuk]

I could swear I checked all the fuses in both boxes and they were all fine

Isn't there 3 fuse boxes?

[muffdan]

Is there? That could be why I missed it then!  s:oops: :oops: s:oops:

[mrivett]

Does anyone know which fuse or which one of the fuse boxes the EVAP fuse is in? I've searched the forum and the handbook to no avail.  I've got the P0443 error after changing my O2 sensors.  s:-( :-( s:-(

[dcod]

I think its in here

 l viewtopic.php?f=11&t=16484&hilit=P0443 l