I am new to the Subaru world my 98 Terzo failed it MOT on
1 Carbon Monoxide excessive 2 nd fast ilde.
2 Exhaust emissions Lamba reading outside specified limits.

I have tested the 3 wire lamba sensor on the downpipe next to the turbo.
Black wire Ground Ok
Grey wire 12v (heater wire)?
Grey wire .228v at idle goes to .334v at around 4K RPM and back to .228v at idle the volts do not seem to cycle. I think they should cycle between (.2v and .9v) is this a duff sensor?

Is there another sensor fitted?

The garage told me that the cat is not fitted! should the other cat be able to cope with emissions,the car is fitted with a de cat downpipe or do I need to fit a new downpipe with a cat fitted to pass the MOT.

 

So you do have a centre cat?
Thats normally enough once its up to temp. The lambda sensor you used is the only one on your model.

 

thanks for the quick response I will check is it located at the front of the engine I am new to Subarus from VWs.

 

No, look from underneathe the car. The centre pipe is the one that joins onto the downpipe and then the backbox. Check it actually has a cat, you should be able to tell from the Subaru stamped heatshield.

 

Checked I have a long pipe fitted from the downpipe to the back box no heatshield no cat!

 

There's your problem.
Check ebay, as you don't really get the centre cats come up much on here. Out something in the wanted section with your location also, someone might loan you one.

 

OP you're also right about the O2 sensor though... A warm engine at steady idle should cause it to continually cycle between 0 and 0.9V! Yours does seem like it's knackered and won't help with the CO tests (as well as the absence of the cat of course).

 

We have Lambda sensors in stock for your model if it turns out you need one

 

The cat in the downpipe is the main one (or not if its been removed). Imports only had the one cat there - no cat in the centre section (just a resonator box). UK specs had the 2 cats - not sure if the centre cat is enough to pass an MOT (others who have tried it will be better informed than us Import drivers )

 

ZEN have their own catted centre and back box to swap out customer's full decat systems, for quickness (i.e. no need to remove the customer's downpipe as well).

I've used this service of theirs and their system has got my car through its last 2 MOTs!

So assuming all else is good with the motor's running, then just a centre cat should be okay to get you through...

 

Got a cat from a member on here when the pipe was delivered the cat was knocked out of the centre pipe (thanks for ripping me off) got another one off E Bay (local to me) fitted the pipe and cat and it Passed the MOT.

 

The member on here more than likely sent the centre pipe in good faith, Never a good idea to send a 2nd hand cat in the post almost certainly get damaged the cat is very brittle