Hi all,

My 03 model Fiesta (1.25LX) recently started showing the engine warning light on the dashboard. I took it in to the local Ford dealer who reckoned it needed a new catalyst and pre-cat hego sensor.

The last MOT (last month, before the warning light came on) was fine except the Natural idle test showed the CO percentage right on the wire - 0.30%vol.

I'm minded to try changing just the sensor, to see if that makes any difference, especially as I can pick one up on the web for much less than the dealer quoted me.

I've therefore two questions for the forum:

i) Is this a sensible thing to do?

ii) How easy is it to fit a new sensor - is it something that I can do myself with an afternoon to spare?

Any and all advice gratefully received! :)

Hi all,

My 03 model Fiesta (1.25LX) recently started showing the engine warning light on the dashboard. I took it in to the local Ford dealer who reckoned it needed a new catalyst and pre-cat hego sensor.

The last MOT (last month, before the warning light came on) was fine except the Natural idle test showed the CO percentage right on the wire - 0.30%vol.

I'm minded to try changing just the sensor, to see if that makes any difference, especially as I can pick one up on the web for much less than the dealer quoted me.

I've therefore two questions for the forum:

i) Is this a sensible thing to do?

ii) How easy is it to fit a new sensor - is it something that I can do myself with an afternoon to spare?

Any and all advice gratefully received! :)

Those sensors can sieze in place and need a bit of heat (blow-torch) to free it off. I would be tempted to use "FORTE" brand petrol system cleaner, at £8.50p + VaT, for a bottle which treats 100 litres of fuel. It will clean the whole system-- injectors, oxygen analyser probe etc., and restore good emissions. I used the diesel version for 8 years, and am now on the version for most petrol engines. There is also a version for the early ZETEC-S engines, to address the sticky-valve problem they have. (pre-Mk 6, they had hydraulic tappets.)

The product is trade-only, and I buy mine from my local Ford dealer, where it is used at services.