How to locte and test O2 sensor

matteb63

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Can anyone help me locate the O2 sensors on my E240 saloon 1999..Is there a way to test them when I take them out?
Thanks
 

turbopete

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2010 '60' Ford Mondeo 2.0TDCi Zetec (sorry)
They are in the down pipes one each side of the small top CAT

http://www.detali.ru/cat/oem_mb2.as...GM=717.463&CT=F&cat=66G&SID=49&SGR=210&SGN=02

I do not think that they can be tested out of the car,but I am not sure on this,, a faulty MAF will put the engine lamp on with this engine

ive never heard of a lambda sensor being tested out of the car. some diagnostic machines have a tester for it. it needs to be running though as the check is for the switching of the sensor. cant remember how it works now. not seen one tested since i had my mondeo 7 years ago!
 

Number_Cruncher

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As has been written, it's best to test a lambda sensor in-situ.

If it's a heated sensor, ideally, you want to check the current which flows through the heater circuit - the high resolution clamp ammeter which Malcolm had found would be absolutely ideal for that task.

The sensing circuit is typically checked for switching, which only begins to happen when the lambda sensor becomes warm enough for the chemical reactions which produce the signal to begin. Once the engine is well up to temperature, you should see switching between about 0.2 and 0.8 volts at about one cycle per second at idle, speeding up if the engine is revved.

What is the original problem? Why are you looking at the lambda sensor?

Sometimes, codes set for lambda sensors in the ECU's memory are not there because the lambda sensor itself is failing, but, becvause there are other faults not picked up by the ECU which are throwing the fuelling out of spec.

Phrased another way, don't buy a new sensor and struggle fitting it until you're absolutely sure that you need to - they aren't a cheap or a trivial part to remove.
 

Alex Crow

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must echo what number cruncher is saying, particularly that testing sensors because an O2 sensor fault code has been logged is not necessarily a good start point. failing air mass sensors for example are far more likely to trigger O2 sensor fault codes than air mass sensor codes - even if the O2 sensors are fine. also, do note that if the O2 sensors show the 'wrong' values this does not mean they are not working correctly. it could be that the mixture is weak because of an air leak or low fuel pressure and they are actually reading correctly.

also, if you are faced with fault codes suggesting 2x failed O2 sensors, you must kow instinctively how unlikely a co-incidence this is! air mass sensor failure is far more common and likely.
 

television

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As Alex above and completely agree
 

LYNALL

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My u581 tester shows lambda outputs, maybe worth buying tester before disturbing expensive sensors?



Lynall
 

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Alex Crow

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that would be a handy way to go lynall, and seeing the %trim on the screen too would help further - eg if lambda was reading low on both sides but trim was +25% this suggests an air mass fault.
 
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matteb63

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can you tell me how many wires and what the colours are..I want to pick up a unerversal o2 sensor before pulling the original one out...Or is that a bad idea?
 

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