ECU Code 6/Engine quickly going through fuel...

So some preliminary research into this little ECT (Engine Coolant Temp) Sensor has told me that this paticular sensor has a lot to do with how the engine runs overall since the ECU uses its readings to make minor fuel/air adjustments on the fly...This is at least what my research has turned up. So is all this correct?

Also the reason why i titled it like I did is simple, I've got this code and I've gone through half a tank of gas in like double time and the car has yet to leave my garage since i completed the EFI conversion....

Also good to note...SOMETIMES (keyword) when I've warmed up the engine to normal idle temp, shut it off for whatever reason and restart, it starts fine but sometimes, like i said, the idle starts jumping up about 500 RPM's at a time from 1000 to 2000 and when this is occurring if you hit the gas pedal the engine starts to die but if you let go before it dies it idles back up to 2000 and the engine is louder then usual at 2000...

Is all this related to this one little sensor???

It could all be related. Won't know until you fix your known problems. The code six is causing your poor fuel mileage.

Well my fuel pump died today so yea...

Lucky you, its a super easy fix, but you alredy knew that from doing the fi swap I'm sure.

Haha Yea I did already know that, I actually replaced my old carb pump for a new one like 10 months ago but started the EFI conversion not long after i replaced it.

However I've still got a code six and i've replaced the ECT sensor for a new one...perhaps i crossed a couple wires when I rebuilt the connectors for the ECT sensor and TW(?) switch...So obviously im going to double check that..but does anyone have any other suggestions while Im checking the wire colors...

There are other two factors in the basic equation to calculate fuel:

(MAP*RPM)/CLT

But you are lucky because you have your ECM telling you a problem with the CLT, but you can look for good electrical and vacuum connections to your MAP sensor & Tacho signal to the ECM as well.

Just more ideas, per your request :)

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Originally Posted by Buzo

There are other two factors in the basic equation to calculate fuel:

(MAP*RPM)/CLT

But you are lucky because you have your ECM telling you a problem with the CLT, but you can look for good electrical and vacuum connections to your MAP sensor & Tacho signal to the ECM as well.

Just more ideas, per your request :)

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I appreciate the ideas, so is it possible I have a bad MAP sensor? I dont know what you mean by "Tacho signal"...The only thing that comes to mind is the RPM signal?....

I checked the tw switch wiring and it was right according to diagram. so the other switch out of process of elimination from the only two plugs and four wires i was working with at the time I repined the plugs, the ECT must be wired correctly...

So why the code 6?

Also I checked on the MAP sensor and found that for some reason...It came into the box from the manifold and teed off, the input plugged into the side, the top of the tee plugged into the MAP and the other just ends with an open end...This didnt seem right and I assumed it would cause a vacuum leak and cause improper readings to the MAP sensor so i took off the tee and plugged the MAP straight in...but now im wondering why my car now idles at 2100 RPM's...can I just dial the idle back down? Or is that really how its meant to be?...

There's supposed to be a plug at the end of the short vacuum line coming from the t. Its there to help stabilize the vacuum pulse. It shouldn't matter too much if you don't have the t, I don't after deleting the black box, my idle is a steady 800 rpms. You could try adjusting your idle. Is it high both when cold and after it warms up? If its just when cold you could also try adjusting the fast idle valve on the back of the tb.

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Originally Posted by pickupman6

There's supposed to be a plug at the end of the short vacuum line coming from the t. Its there to help stabilize the vacuum pulse. It shouldn't matter too much if you don't have the t, I don't after deleting the black box, my idle is a steady 800 rpms. You could try adjusting your idle. Is it high both when cold and after it warms up? If its just when cold you could also try adjusting the fast idle valve on the back of the tb.

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Well....thats the thing...I dont have the coolant lines connected to the valve because one of the stems broke off during the conversion and I never made a pepsi can gasket to cover the holes and basically delete it...So could this NOW be the problem?

EDIT: Also I knew it shouldnt matter because i've seen people's setups with deleted black boxes. They all have the MAP directly connected.

Yeah mines still runnin rich and i have the egr blocked off and that's the only code i get.Efi is a lot harder to figure out than carb.Got a new air filter cumin on monday so maybe that will help,also gonna try to bump timing.

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Originally Posted by Susanoo

Well....thats the thing...I dont have the coolant lines connected to the valve because one of the stems broke off during the conversion and I never made a pepsi can gasket to cover the holes and basically delete it...So could this NOW be the problem?

EDIT: Also I knew it shouldnt matter because i've seen people's setups with deleted black boxes. They all have the MAP directly connected.

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Bing that's your problem. It thinks the engine is cold so the valve stays open and creates a vacuum leak, causing the rpms to be high. Still won't solve your poor mpg's though.

Yea I blocked the holes off with a pepsi can gasket and bolted it back on, It ran way better and with the MAP sensor connected directly now, the whole engine runs extremely better and the exhaust no longer sounds like a machine gun.

So back to the ECT(Code 6) error...where do I go from here? I replaced the sensor...the only other thing i can do is test continuity...

That's about all that's left to do besides testing the ect to be sure its good. And if both check out good it could be an issue with the ecu. What color was the plug on the ect sensor you changed? Just making sure you changed the right one because most parts stores will give you the fan switch instead. The green plug is for the fan control. I'm sure you know this, just throwing it out there.

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Originally Posted by pickupman6

That's about all that's left to do besides testing the ect to be sure its good. And if both check out good it could be an issue with the ecu. What color was the plug on the ect sensor you changed? Just making sure you changed the right one because most parts stores will give you the fan switch instead. The green plug is for the fan control. I'm sure you know this, just throwing it out there.

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Well actually I debated that when i changed it because I thought the ECT was the big one and it was actually the little one. I dont remember which is which but I think ECT is green? My fans work so it must be correct..

I'll have to do the continuity test later today. Even with the MAP sensor getting a good reading now, the engine runs twice better and I can tell from the exhaust smell that its using much less gas then before. I just want to fix this ECT issue before taking it through emission testing :P

Ok I remember this much the ect is the one closest to the block, I just checked and its the green one. The manual says to check voltage between ylw/grn(+) and body ground, there should be about 5 volts. If there's not trace the y/g wire bac to the ecu (c6). Next be sure there is 5v between y/g(+) and grn/wht. If thers not trace the g/w wire back to the ecu(c12).

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Originally Posted by pickupman6

Ok I remember this much the ect is the one closest to the block, I just checked and its the green one. The manual says to check voltage between ylw/grn(+) and body ground, there should be about 5 volts. If there's not trace the y/g wire bac to the ecu (c6). Next be sure there is 5v between y/g(+) and grn/wht. If thers not trace the g/w wire back to the ecu(c12).

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Indeed, it's the exact same on mine. I'll check for this voltage and get back to you....

So i checked on that voltage and with + on the yellow/green i got a little over 3 volts for both readings, - to body ground and to the green/white. This was while the car was running.

Hmm well it says approximately 5v so maybe that's ok, idk. I will try to check mine out tomorrow but my guess is that's a little low. Have you tested the ect?

Well no, i bought a new one so i assumed it was good :/ i know the testing procedure for it but it may be a couple days before i get back on that. Could the ecu be bad or "weak"?

Its possible. Sorry I never got the chance to check mine, been working 16 hour days. I will try tomorrow.

Oh yeah I'm thinking you need to unplug it to get the 5v, the ect is a thermo resistor, which changes the voltage as the car warms up. At least that's how I figure it to work but I will try to check mine tomorrow.

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Originally Posted by pickupman6

Oh yeah I'm thinking you need to unplug it to get the 5v, the ect is a thermo resistor, which changes the voltage as the car warms up. At least that's how I figure it to work but I will try to check mine tomorrow.

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Yea thats how i figure it would work...different voltages meaning different temps. However, I did unplug it to check the voltage :P I went to PaP today but there were no manual cars so I didnt grab an ECU. I dont know if theres a difference between ECU's with a manual or automatic tranny. I have a spare one I pulled from an automatic...

I know that people who have switch from auto to manual trans have used they're auto ecu but don't know if it works the other way,manual to auto.

Aww dang, I forgot to check mine out today.

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Originally Posted by pickupman6

Aww dang, I forgot to check mine out today.

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I hope you can do that soon man, I actually took the car to a place since I failed local emission testing. CO was really high, if you wanna know but HC was only 15 points off. They tested all the sensors related to emissions and said they were ok, but that the O2 sensor was responding a little slowly. So that could also be part of the extra fuel usage, a faulty O2, but then again I still dont have the other manifold on.

So...I guess i'll try the other ECU and see if anything changes. Oh and im still gonna check that ECT sensor myself just to be sure...in the end I somehow pissed the mechanic off...somehow I asked "too many questions" and therefore told me "not to bring my toy back" so...yea I'm not sure im gonna trust his testing results too much...

Well I went by the shop to get my hatch and bring it home today and grabbed my dvom. I unplugged the ect and tested the car side of the plug with key on engine off and it said 4.999-5v. It was dark so I couldn't check it with it plugged up and running. I will do that tomorrow.

dont be concerned with the 5 volts at the ect plug, its the voltage getting back to the ecu thats the important bit.
the tw sensor is a negative temperature co-efficient thermister.
which in plain english means the resistance of the sensor drops as the temp rises.
check the resistance of the tw sensor with the engine cold and as it warms up to normal operating temp.
it will start prob somewhere from 500 ohms or more and will be down to 50 or less when its up to temp if its fine.
the ecu sends the 5v to the sensor and measures the voltage that returns to the ecu, which will rise as the engine warms up, if the sensor is open circuit , there is no return voltage to the ecu, and it will stay in the cold start / warm up maps, which happen to be quite rich in the fuel mixtures and would explain the poor mpg.
if there is no resistance across the tw sensor, replace it, if the resistance is very high( ie still a few hundred ohms when its warm ), replace it.
if it checks out, check the continuity of the return wire between the plug and the ecu plug. dont forget to unplug the sensor before you measure it and disconnect the batt and ecu before checking for continuity between the plug and ecu. no continuity or high resistance, replace the wire.

Kinda already said that the voltage will change depemding on the engine temp, but thanks for confirming it.

Thanks, Hauntd ca3, for your detailed information. I've unplugged the car from power for the last 5-6 hours in hope that it'll clear the ECU to make sure this code isnt just still stored from after replacing the sensor. I've still yet to test the sensor, but I do wish to be more clear...the voltage I read and reported was the voltage at run/idle.

I'll try to get around to testing the sensor and wire. I just hate tracking down wires from one part of the car to another :P

So...I left the positive cable unplugged for about 16 hours and I still have code 6, so after I come back from some errands I plan on mapping out that circuit and checking the wires.

First I would unplug the ect and make sure you have 5v with he on engine off. If you do than next I would test the new ect. Just because its new doesn't mean its good.

Btw it only takes 30 seconds to reset the ecu

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Originally Posted by pickupman6

First I would unplug the ect and make sure you have 5v with he on engine off. If you do than next I would test the new ect. Just because its new doesn't mean its good.

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Im assuming you mean the key on, but the engine off...I get 1.65. With the engine running I read about 2.4...Im getting a lot of interference from the plug wires and its about time for replacement...maybe this is complicating matters? I've never seen such a thing happen before and I figure its odd so I thought I'd throw it out there too. Im gonna look back over the testing procedure and recheck the numbers, then test the ect. However with such low voltages and the fact that these numbers have dropped since I last tested it, I'm thinking its not the sensor but either the ECU or the wires to and from.

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Originally Posted by pickupman6

Btw it only takes 30 seconds to reset the ecu

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Thats what I thought but I guess code 6 pops up fast with voltages as low as they are...

If its reading that low unplugged , I would say its a bad ecu.

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Originally Posted by pickupman6

If its reading that low unplugged , I would say its a bad ecu.

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Well I replaced the ECU and im now getting 3.6 volts, engine running....

UPDATE: I decided to also check that everything was wired point to point correctly...apparently I wired the two sensors incorrectly...

On the ECT I have the green and white (sensor ground 2) on the white and green from the sensor to the left of the ECT. I forgot what that sensor is called and what it does. However, since I found this im gonna rewire it and see if anything changes.

So I went back and finally swapped those wires around and now im getting code 10, IAT sensor. wtf? It never gave me anything but code 6. Soo...I could trace all this around all day. But someone out there has to be able to give me a good explanation as to what could have happened...I cant possibly have wired everything wrong and for it to give me just code 06...

So does that mean you no longer are getting the code 6?

When I checked yesterday, it was only spitting out code 10. However I also notice that my radiator fans dont cut off since I swapped those wires. What could I possibly have done?

Update: I did some testing for the wires going to the IAT sensor. On the + side I get over 7 volts and for the - side I can read 3.3-3.6 volts...Gonna look up some testing info to see what this could translate to but any info could help...