Z3M Failed MOT!

[Medskipper]

Hi all,

surprised to have my Z3M fail it’s MOT this week!

I am told by the tester that it needs a new Lambda sensor or as some would say O2 sensor.

when I asked which one (as there are two) they said can’t tell you until we put it on the
computer to test it!

question 1. How can the mot tester know it’s the O2 sensor if he hasn’t diagnosed it on his computer?
Q2. what sort of cost does it involve as they tell me both should be replaced?
Q3. How difficult is the job?

p.s. S50 engine and year 2000

many thanks

 

[GazHyde]

11781406981 looks to be the part number for both.

lllparts.co.uk shows OEM around £220 per sensor (may get cheaper from local dealer), eBay take your pic from £130 per sensor.

RealOEM.com - Online BMW Parts Catalog

BMW parts Z3 E36 Z3 M Catalyst/lambda probe

www.realoem.com

 

[Medskipper]

11781406981 looks to be the part number for both.

lllparts.co.uk shows OEM around £220 per sensor (may get cheaper from local dealer), eBay take your pic from £130 per sensor.

RealOEM.com - Online BMW Parts Catalog

BMW parts Z3 E36 Z3 M Catalyst/lambda probe

www.realoem.com

View attachment 230453

Interesting! Looking up Lambda Sensors on AUTODOC for my Z3M the prices are only around £30. Each! They have my vin number so should be showing the correct sensor?

https://www.autodoc.co.uk/car-parts/lambda-sensor-10148/bmw/z3/z3-e36/7750-m-3-2?fromSearch=1

what am I missing?

 

[GazHyde]

what am I missing?

With Autodoc about 2 weeks delivery. Seriously though I'm sure you can buy cheap ones, can't tell you how good that brand is though!

 

[Nodzed]

I think the consensus on here over the last few years had been when it comes to sensors, buy cheap buy twice.

 

[Medskipper]

I think the consensus on here over the last few years had been when it comes to sensors, buy cheap buy twice.

yes I understand that sentiment completely, however AUTODOC will supply Bosch sensors for around £60. I assume these should be good quality?

 

[Scooblitz]

Bmw Dealer was £234 for a Lambda for my MOT in March on my 2.8i.

 

[Stevo7682]

A lot of the cheaper sensors are not plug and play and need to be wired in .
I'm guessing that he is leaning towards the lambda because of the emissions results.
Stephen.

 

[colb]

Ideal thing to do before firing the parts cannon is to scan the car and look at live data from the O2 sensors to see if they are performing.
Pre Cat sensors should be showing up in graph form in live data as a rising and falling wave form as the voltages range up and down. Post Cat sensors if all is well with what they are seeing are preety static when viewed. The tester probably found high exhaust readings and presumed the cause was faulty O2 Sensors. There are however other possibilities for high readings, air leaks in the vaccum system will be picked up in the exhaust and lead the ECU to think the engine is running lean and demand more fuel at the injectors to richen the mixture up. If it is an air leak the ECU will demand up to 20% more fuel to be injected, it will do this then realise thats not fixing it and set the EML on your dashboard to draw attention to the fault. Another possible cause would be a failed or failing Maf sensor that is misreporting the amount of air passing through it. Also worth looking at live data from the fuel trims to see if they high, a sure sign of something amiss with the vaccum system, O2 Sensors or Maf. Some in depth diagnostics required before firing the parts cannon is the best course of action.

 

[Medskipper]

Ideal thing to do before firing the parts cannon is to scan the car and look at live data from the O2 sensors to see if they are performing.
Pre Cat sensors should be showing up in graph form in live data as a rising and falling wave form as the voltages range up and down. Post Cat sensors if all is well with what they are seeing are preety static when viewed. The tester probably found high exhaust readings and presumed the cause was faulty O2 Sensors. There are however other possibilities for high readings, air leaks in the vaccum system will be picked up in the exhaust and lead the ECU to think the engine is running lean and demand more fuel at the injectors to richen the mixture up. If it is an air leak the ECU will demand up to 20% more fuel to be injected, it will do this then realise thats not fixing it and set the EML on your dashboard to draw attention to the fault. Another possible cause would be a failed or failing Maf sensor that is misreporting the amount of air passing through it. Also worth looking at live data from the fuel trims to see if they high, a sure sign of something amiss with the vaccum system, O2 Sensors or Maf. Some in depth diagnostics required before firing the parts cannon is the best course of action.

excellent, many thanks for a well thought out reply!
I will indeed check all out.

 

[t-tony]

excellent, many thanks for a well thought out reply!
I will indeed check all out.

Post a copy of your MOT emission fail certificate and then we will have a better picture of why it failed in the first place.

Tony.