Suzuki Grand Vitara MOT fail emissions

[blueg33]

My son has a 2004 Grand Vitara with the 2.0 petrol engine.

It has just failed its MOT on emissions but we are not sure why.

It has 2 lambda sensors one upstream and one downstream of the CAT, and according to the OBD reader they are both showing the correct readings. The EML light is not on and there are no error codes.

I would have thought that if the cat was faulty then the downstream sensor would be showing the wrong readings?

The thing we haven’t done yet is put an oscilloscope across the lambdas ti check the rate of change of voltage is correct, but I would have expected the OBD to spot that or the ECU to light the EML.

Thoughts?

[stevieturbo]

blueg33 said:

My son has a 2004 Grand Vitara with the 2.0 petrol engine.

It has just failed its MOT on emissions but we are not sure why.

It has 2 lambda sensors one upstream and one downstream of the CAT, and according to the OBD reader they are both showing the correct readings. The EML light is not on and there are no error codes.

I would have thought that if the cat was faulty then the downstream sensor would be showing the wrong readings?

The thing we haven’t done yet is put an oscilloscope across the lambdas ti check the rate of change of voltage is correct, but I would have expected the OBD to spot that or the ECU to light the EML.

Thoughts?

Well if you failed the test, they would have given you a results sheet of that emissions tests which would give details why. So post the full emissions test results.

And your OBD reader has nothing to do with it

[blueg33]

They thought it was a sensor fault hence the OBD check

[Scrump]

What were the emissions tests results?

[blueg33]

Have asked junior to send them to me.

[blueg33]

Not sure it was emissions on checking certificate

The fail is stated as

Exhaust Lambda reading after 2nd fast idle outside specified limits (8.2.1.2 (c))

[TwinKam]

OK ...'Lambda reading outside limits' does not mean that there's anything wrong with the 'lambda' sensors... what is wrong is calling them that, it's confusing, call them oxygen sensors and remove that confusion.
The 'Lambda reading' is an artificial man made quotient that = 1.0 if the balance of all the measurable gases at the tailpipe is correct. That's why we need to see the test results, it will highlight which gas is out of kilter.
Notice that I said 'at the tailpipe'... this is where they are sampled, not at the engine end of the exhaust. A very common cause of 'lambda reading outside limits' is a simple exhaust leak, which pulls in air (Oxygen) throwing the balance of the gases out at the tailpipe despite them being perfect upstream. Yes, it's possible to fail an MoT emissions test because your exhaust is too 'clean'!

[E-bmw]

At the risk of repeating all of the good advice above without the results we have no idea what to tell you, except that there is currently a number of reasons for the failure.

[blueg33]

E-bmw said:

At the risk of repeating all of the good advice above without the results we have no idea what to tell you, except that there is currently a number of reasons for the failure.

I get it. We have a problem, the MOT centre didn't give junior the emissions print out and there is no detail on the MOT failure document

[E-bmw]

blueg33 said:

E-bmw said:

At the risk of repeating all of the good advice above without the results we have no idea what to tell you, except that there is currently a number of reasons for the failure.

I get it. We have a problem, the MOT centre didn't give junior the emissions print out and there is no detail on the MOT failure document

In that case you need to go back to them & get one.

If they can't provide the one they failed it with they will need to do another emissions test to produce one, without it you are pretty much going to throw several £100's at the car in the hope of fixing something that (as above) could be a simple air leak in the exhaust.

[blueg33]

E-bmw said:

blueg33 said:

E-bmw said:

At the risk of repeating all of the good advice above without the results we have no idea what to tell you, except that there is currently a number of reasons for the failure.

I get it. We have a problem, the MOT centre didn't give junior the emissions print out and there is no detail on the MOT failure document

In that case you need to go back to them & get one.

If they can't provide the one they failed it with they will need to do another emissions test to produce one, without it you are pretty much going to throw several £100's at the car in the hope of fixing something that (as above) could be a simple air leak in the exhaust.

Agreed. I have told junior to get the printout, or go to another garage and get the exhaust gasses retested

[E-bmw]

blueg33 said:

E-bmw said:

blueg33 said:

E-bmw said:

At the risk of repeating all of the good advice above without the results we have no idea what to tell you, except that there is currently a number of reasons for the failure.

I get it. We have a problem, the MOT centre didn't give junior the emissions print out and there is no detail on the MOT failure document

In that case you need to go back to them & get one.

If they can't provide the one they failed it with they will need to do another emissions test to produce one, without it you are pretty much going to throw several £100's at the car in the hope of fixing something that (as above) could be a simple air leak in the exhaust.

Agreed. I have told junior to get the printout, or go to another garage and get the exhaust gasses retested

No, go back there, AFAIK if there is an emissions failure they have to give you the print-out, so should do it for free or give you the one from the test.

[stevieturbo]

blueg33 said:

Not sure it was emissions on checking certificate

The fail is stated as

Exhaust Lambda reading after 2nd fast idle outside specified limits (8.2.1.2 (c))

that is emissions, and we're still waiting on those results.

[blueg33]

stevieturbo said:

blueg33 said:

Not sure it was emissions on checking certificate

The fail is stated as

Exhaust Lambda reading after 2nd fast idle outside specified limits (8.2.1.2 (c))

that is emissions, and we're still waiting on those results.

See comment above

[stevieturbo]

It's bizarre that any legitimate MOT tester would fail you, and then not give you the information from the test, that is essential to evaluate the fail, and for whoever is intending to work at it.

If they cannot provide full emissions test results, I'd be reporting them to the DVSA.

[blueg33]

Finally have the test results:




The garage told junior that they thought it was a sensor fault, thats why he checked the sesors

[stevieturbo]

shouts more of an air leak in the exhaust.

[TwinKam]

Absolutely, as suggested earlier because it's very common, more common than failed sensors. It doesn't throw any codes or affect the running because it's all happening downstream of anything important or sensed... apart from the MoT examiners probe.
Go all over the exhaust with a length of tube stuck in your ear, and you'll find the leak easy enough. Oh the engine needs to be running...

[E-bmw]

As above, the readings are fine apart from the oxygen in exhaust gas reading, it will 99% be an air leak.

[blueg33]

Thanks all. I have suggested he gets under the car with a bit of hosepipe to his ear.