Hello, My 02 Focus ST170 has failed the MOT on the emissions. The engine management light has been on for a while and does not seem to affect running it at all. The light will go off sometimes and then comes on again. The garage code read and said its on eof the 2 lambda sensors or the cat. I ve replaced the pre cat sensor and the light has come back on again. Is there anyway of telling whether it will be the other sensor or the cat? The post cat sensor is something like £80 and i ve already £60 on the pre cat one. Any help much appreciated.
Sam

 

Hi Mate,
Have a look at this site. http://www.fordst170.co.uk/
It’s quite common for the LAMBDA sensors to go. You need get a BlueFin error code reader on it to find out which one. TOTD uxbridge have one or take to a ford specialist "Advanced Auto technik in Slough" who can check it woth OE ford software and clear the error code after you have replace the other sensor.
I replaced both sensors and then 3 months later replaced the CAT. Never seen the engine management light since.

http://www.fordspecialists.co.uk/page2.html

thanks,
Manoj

 

i have a cat for the st in mint working condition you could borrow to put it thru its test

 

What was the fault code? Its a bit silly willy nilly changing bits until you know what is actually at fault.

If its running over rich for a while then that has probably fooked the cat too.

 

deffo the lambda, there weak and crappy

 

Thanks for the replies, I spoke to local ford dealer and they wouldn t guarantee to tell me which lambda sensor it was from diagnostics and wanted £65 as well. I ve replaced the front lambda (pre cat) had it re tested still failed and light came back on again after about 200 miles. So Im now left with either replacing the other sensor or the cat. I read somewhere that the post cat sensor is the same except for the plastic lug on it. I now have a spare pre sensor, any chance this can be used as a post cat sensor?

RSBENJ1 That is a very generous offer, how much do you think postage would be and when could you send it? thanks again. Also does it have the lambda sensors in still?

 

It's very likely to be the same sensor, other than the usual connector, ford will change this to try and justify why it's much more expensive!!
Try and check the switching speed, if this is low on the post cat, it will/can give problems, I've replaced sensors on cars that have passed on emissions, but shit mpg, replaced the sensor mpg shot up big time, as was only the slow switching speed the problem.
tabetha

 

Bollocks that ford can't tell you which sensor it is, you will have a fault code present, that will tell you which sensor is at fault, and what is actually wrong with the sensor. They just want more money out of you.

I am in Devon mate on saturday for 4 nights, I have got a fault code reader that can read the faults off for you. If its any help to you, pop along with the car and I'll do it for you no bother. Might be a bit of a trek for you though, its up to you!

Rich.

 

Rich170, thats very kind I may well take you up on that. I ve order a bosch post cat sensor now which should be here tomorrow so fingers crossed its that.
When I phoned Ford and they said they couldn t say for certain I thought that was a load of bull because thats the whole point of a diagnostics system.
From trawling all the posts changing both the lambdas isn t a terrible idea anyway for running and fuel, well this is how Im justifying the £120 in my mind!

 

Sounds mad that, I'm sure the lambda I bought from ford for my st170 was about £30.

I'll be at ladram bay holiday park on saturday for 4 nights, just let me know if you want to pop on over!

 

Sounds like rear lambda sensor. If its buggered you ecu will be all over the shop too.
Macca

 

In what way would the ecu be all over the shop mate?
The sensors were £70 and £90 from ford or both around £60 from local motor factors.

 

i dont really know but should not be no more than £20 i dont think