I have recently had to replace my upstream O2 sensors in my 2002 model ( 12/2001) XJ8. I was puzzled as to why I got the 1646 and 1647 DTC's without the EML coming on.

The penny didn't drop until I switched the ignition on and there was no EML lit, I've had the car for a year???

I split the instrument cluster to see what the problem was, only to find that LED 11, the EML LED had been snipped out to prevent it showing a fault.

What I said about the person who did this doesn't bear repeating'

I am handy with a soldering Iron, but not sure about what LED to replace it with??

My electronics knowledge and dealings with them ended when I retired, so help in identifying the correct LED would be a great help.

I would hope my local Maplins should have a suitable stock. Would I be correct to assume that they are 12v LEDs?

Thanks

Bill W

 

On the subject of LED's all the ones on the cluster appear to be white. If I shine a white LED torch on the back of the dials where the LED's shine, the image of say the EML shows as white. There are no coloured lenses of any description on either the LED's, nor where they shine through the panel face ?????? Any panel light illuminated by a bulb ie indicators, main beam, seatbelt, have coloured lenses. All lit by LED haven't any at all, are the LED's normally illuminated RED when lit??
Bill W.

 

There is no such thing as an 12-volt LED, LED's can be hooked up to all voltages providing you limit the current going through them to 20milli amps. The electronic circuit in which it operates is already set to the correct amperage so you just buy a LED.

Now for the color, although some LED's have white or transparent housings they can light up red or whatever color. If you want it red you buy a red LED.
In my BMW the check control light is lighting up either orange (no problems just a check before you start) or red (there is a problem). This is done with a bipolar LED, it can light up in different colors.

When putting it in be aware of the polarity, if you use a standard red LED and it doesn't light up before you start you have to put it in the other way around. It is better to check it before you build everything back together.

Hope this helps. If you got any more questions about the subject please ask.

 

Hi Nick,


I realised that the led was a diode and as such was able to be put only one way round. Is it possible to meter an LED to determine which the forward bias condition is?


Cheers
Bill W.

 

Hi Bill,

An LED is indeed a diode, you can see through the housing to determine the + and - terminal. On the outside it is the flat spot on the side that determines the minus.

This pic will help, no need to measure it this way.




Another way is to look at the 2 contacts, the longest is always the positive terminal.

 

Hi,
Finally got round to installing the EML LED. All went to plan. After putting the Instrument panel in and testing it, I have found that the EML comes on on ign on and stays on with . Fully expected as I have a faulty upstream . The problem I have is that it doesn't stay on, seeming to go out when the engine gets up to temperature. What is the Ign on colour of the EML and what is the engine on state if a fault is present? I know some are Orange with Ign on and go Red to indicate a fault.. Confused at the moment because my EML had been cut out to stop it coming on so I don't know if they are the same as the other LED's on the board or are bi-polar 2 colour? ie Orange/Red. Could someone check for me at all?? The car is a 2002MY XJ8 4.0 ltr L.W.B.


*****UPDATE*****
I had the faulty O2 sensor replaced yesterday. The EML comes on RED on ignition on and goes out with engine on, as expected. Once again it stays out if I do a run, get it warmed up, then stop and turn the engine off. On turning the ignition on again with a warm engine the EML led doesn't come on?? With my limited knowledge I would suspect a Bi-Polar LED in the EML slot? I checked a 1998 XJ8 and on Ignition on it lights up Orange saying "Check Engine" and goes out with engine on. I would like to get to the bottom of this if anyone has any suggestions????

Cheers

Bill