jonesy79

hi all my check engine light has come on again first it was knock sensor then lambda sensor but this 1 puzzles me it came on and off yesterday for few seconds and again this morning now it stays on i have plugged black and green plugs in again but it doesnt flash like b4 to give me the code also it is now idling at around 1.5k then back down to below 1k can any1 help me make any sense of this please thx lee

Glowplug

iTrader: (8)

Try resetting the ECU. Then see what you have.

jonesy79

lol soz how do i reset ecu also dont know if this makes a difference the cars a import

Glowplug

iTrader: (8)

You can follow these instructions, or disconnect the battery for an hour (or over night).

Import doesn't make a difference at the moment, but more details of the car would help, year and any mods etc.

jonesy79

its a 1994 import totally standard

Splitpin

Disconnecting the battery for a period longer than a few minutes will reset the ECU but doing it this way is a counterproductive, bad idea. Using the black plug + green plug + drive routine as per JGM's website runs an active error check on all the car's systems. If it doesn't complete correctly, it is because there is a current problem that must be fixed.

If your check engine light went on, then went off again, it's because there was an error state that then cleared up by itself. If it has come back on, and stayed on, that's because there's an error state that is there right now. As above, if you can't reset the ECU via the black plug + green plug procedure - and get an error code instead of the on/off/on/off equal flash "OK" code, it's because something's broken - whether an item of equipment connected to the ECU, or the wiring loom between the two components.

Short answer is that if your check engine light is on constantly, and you can't reset the ECU via the proper procedure, you need to fix something.

Glowplug

iTrader: (8)

Counterproductive, yes. But the OP states that the CEL is not flashing as expected during diagnostics, (assume no steady on/off and no code) so my thinking was 'a clean slate' by dropping the battery and the 'if' there is a fault it would flash up on the first drive.

No offence Splitpin, just explaining myself.

Splitpin

I know bud, none taken. Underlying point remains that if the standard reset procedure won't complete, there are only two explanations. Either there's a problem, or the user hasn't left it go on long enough to time out (and show a problem).

Either way, persevering with the reset procedure is the best way to learn what's up. There's a timeout built into it - on the later classics it's 300 seconds if I remember right. If it hasn't okayed by the timeout, it automatically tells you what sensors aren't in spec. One way or the other, in other words, it will/must give either an okay or an error.

jonesy79

hi done the ecu reset and engine light still on and wont give any codes when black and green plugs connected also wont start in mornings takes a few turns of the key runs lumpy for few seconds and cuts out if any revs are given but ok after minute or so also engine fans are on constantly even after car has been standing overnight any advice more than welcome thx

kevin wrx

iTrader: (1)

u are remembering to disconect black and green wires after looking for fault codes.

kevin wrx

iTrader: (1)

check all the earth straps to the battery incase its a dodgy earth,as had a problem and it was down to a faulty earth if u are near essex i would go through fault code procedure with you.

kevin wrx

iTrader: (1)

faulty fan switch causing fans to come on a dodgy battery causing voltage drop and causing fan to kick in but all these are assumptions and not by all means correct.

jonesy79

thx kevin will have a look at that in morning any thoughts on why it wont start first time after been standing overnight it runs just as well as b4 when temp comes up a little dnt know why it wont flash the codes as it did a few moths ago and i had to change knock sensor then it told me codes again few weeks later when i had to change lambda sensor but this time it doesnt flash when plugs are connected just stays on

Splitpin

How did you do that? Via disconnecting the battery or doing it the proper way - via the black and green plugs, and then going for a drive? Need to know things like this in order to know what you have and haven't done.

That's hardly surprising. Connecting the black and green plugs starts the reset sequence. If all you want to do is check for stored errors, you connect the black plugs only. Try that and tell us what happens.

kevin wrx

iTrader: (1)

ther is another way of fault code check and that is just connect the black wires and turn ignition till the check engin light comes on but dont start the car then check the fault codes,thatsthe way i check em and there is nothing wrong diong it the other way either.

Glowplug

iTrader: (8)

Poor cold starting caused by Coolant Tempreture Sensor on the way out. Could also be the cause of the fans running and the constant CEL too.[/COLOR][/I][/B]

Splitpin

What exactly is the "other way" you are referring to Kevin?

There is only one method of checking stored fault codes (without using an external diagnostic computer), and that's via the black plugs on their own.

As above, connecting green + black together initiates the ECU reset sequence.

Splitpin

Most probably. If the OP can learn how to read the memory properly, it'll probably become abundantly clear. .

kevin wrx

iTrader: (1)

sorry mate thats what i mean just use the black plugs it sounded like he was connecting green and black together to check for codes.thats one thing i like about coming on here is the help u give mate as in my book anything from u is normally 100 per cent

jonesy79

hi all well i must fess up i have been trying to read faults wrong well anyway i have found fault 21 which i belive to be engine coolant temp sensor as you have mentioned now i belive this to be located below air inlet pipe on the block is this correct and how much of a job is it to do thx again you are all very helpfull

Splitpin

That's more like it.

Yes, there are two coolant temp sensors on your model year of car - one feeds the needle in the instrument pack, and the other the ECU (which is the "bigger" one of the two).

They're located next to each other, in the front edge of the coolant distributor main which runs across the top of the engine underneath the inlet manifold. Look behind the alternator and you'll see them sticking out. Clearly you'll need to (part-)drain the cooling system to change it - or prepare to get very wet!

jonesy79

well thank you i shall tackle this problem on the weekend and give full service at the same time thnks again very helpful