Help please took my Mondeo 2005 2.5 ghia x for a MOT and when I got the car back the engine management light was on.

When a diagnostic check was done it said both Lamda sensors were faulty,Garage checked the connections sprayed them with wd40 and bingo problem gone.

Unfortunatly 10 miles down the road the engine management light has come on again.Now been told both Lamdas are faulty and will cost £400 to replace.

The car had done just 70.000 miles any advice please

Thankyou in anticipation

Oh God... WD40 strikes again.

You don't ever squirt WD40 on electrical stuff - not ever. It's a penetrant, and given that it is not a sentient being therefore does not know rust from solder, it also penetrates solder and destroys circuits. It also isn't a lubricant. If you attempt to lubricate anything with it, it'll work for a brief period, before the residue becomes nothing more than a muck magnet. Any responsible garage should know all of this.

[edit] Oh and for the record, in case it isn't clear enough - I have a seething hatred for WD40 and the way it is marketed as a "wonder tool to fix anything" - it's not. It breaks stuff. It's OK for getting rusted bolts off, and that's about all it should ever be used for. If it were up to me, I'd ban the !Removed! stuff.

I disagree.... I find its very good at stopping household squeaks ;)

As for the use of it on the Lambda, its pretty much doomed. The best thing you can do now is replace it sadly...

Does it really ruin circuits? I lost count how many times we sprayed WD-40 on our old telly every time a drink was spilt down the back of it and it always worked a treat lol

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Yes, it really does. It's also highly flammable so it's a wonder you didn't burn your house down spraying it on live circuits (or circuits which were live soon after spraying).

But most of the flammable ingredients will evaporate quickly. Its even designed to be sprayed on circuits to remove moisture (when unplugged).

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Just found this so this is probably why my house didn't burn down.

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How did they test the senser or they just sayin throw 2 sensors at it because it shows a fault code

They used a plug in diagnostic handheld machine.I am a little concerned after some of the replies ie using wd40 !

Just because it throws up a fault I wouldn go replacing them at that price they must be egits if they think spraying wd40 goin fix it needs be properly tested

The only thing highly flammable about wd40 from an aerosol is the propellant, wd40 does burn but spraying a little on something hot just causes white smoke! I have sprayed it many times onto red hot parts! To add to that, wd40 is rubbish as a penetrating spray for removing bolts, seems to be a popular misconception that it's main use is for that!! Maybe the fact that WD stands for water displacement has a hint at its use.. However...

Strange that 2 lambda sensors become faulty just like that! Time to get another opinion and don't pay £400 for 2 sensors!!

if they physicly removed the sensors and sprayed the tips with wd40, then they need their heads tested

if they just sprayed the wiring plugs without removing the sensors, then no harm will have been done.

find it odd for two sensors to fail suddenly, especially as its just passed its mot, which it wont have done with bad sensors.

i believe there is a fuse for the heater circuits on the 02 sensors, so worth checking that first.

beyond that, would never condemn the sensors just because of fault codes, have them tested properly,

there are a number of codes that can be flagged for the 02 sensors, for eg, a lot of them could indicate a problem elsewhere in the system that are causing the 02 sensors to struggle to cope...such as fuel pressure too low, injectors leaking and a whole lot more.

having fuel trims checked, and viewing a graph of sensor switching takes little time and can tell you a lot if you know someone you can trust with the right equipment...i wouldnt go with the garage youve been using for this.