Ok really need help here, this is the most in depth i have ever gone and need people that really understand cat converters, exhaust gases and o2 sensors.

My garage tell me that i need a new catalytic converter on the left side Bank 1 (uk car).

i keep getting p0420 catalyst below efficency threshold bank 1

i also got a p0102 code today mass or volume air flow circuit low input

 

nobody?

any techs around?

 

Give them a chance Darren!

 

sorry, im being impatient i know, just a little stressed, appologies.

 

See your other thread re O2s. SHRT will be Short. FT=fuel trim. B=bank. S=sensor (guess).

You may struggle to see what's happening if you can't record & graph but have a go.

P0102 - see other thread but it's not MAF. Read the codes PDF from JTIS!

 

Ive just figured out the fuel trim thing thanks jagv8, does fuel trim relate to a o2 sensor? My data tells me that short term fuel trim bank 1 sensor 2 is not availible but do we have seperate fuel trim sensors?

also regarding the p0102 i pulled this from the jtis


P0102 EMS
OBD II
MAF Sensor circuit low voltage Ignition ON 10 seconds 2 A ECM Default:
– Default air mass used
– Adaptive fuel metering
inhibited
– Catalyst warm up ignition
retard inhibited
– Canister purge inhibited
– Maximum engine speed
reduced
PI1
-044
Blocked air cleaner
Air intake leak between MAF Sensor and
throttle
MAF Sensor to ECM sensing circuit:
high resistance, open circuit, intermittent
short circuit to ground
MAF Sensor supply circuit:
open circuit, short circuit to ground
MAF Sensor failure

 

Sorry!!! It is MAF. grr. Dunno what I was doing.

Fuelling could be anywhere if it's iffy MAF.

 

There will be STFT each bank (also LTFT, which can diagnose e.g. air leaks).

By "will be" I mean: the car has. Up to your tool to reveal them!

Fuelling is aimed to be nearly right but it can only tell by going rich then lean then rich all the time. Uses upstreams to tell. Cats should then sort out the slight richness. Which is why the downstreams should not cycle much. If they do, the cat is no good.

The reason it has to cycle is that the O2s do not really measure as one would like (later kind on my car do). They just read lean or rich, not by how much (whereas the later ones do).

 

Jagv8 im trying my best to keep up with your knowladge but i am struggling so forgive me.

how do i get my tool to reveal them? and by this do you mean where they are?

also how do i tell if my cat is bad by my readings?
If you look at my pictures you can see that all four o2 sensors are working and two of them are higher than the other two ( upstream and downstream of course)
so to me it looks like everything is ok, but you seem to know what you are talking about so please in laymans terms help me to diagnose whether i need a new cat or just to replace the o2 sensors or fuel trim sensors?

p.s when i took these pictures car was at idle but fully warm after a bit of a thrash.

 

The numbers should keep changing (high & low as it goes between rich & lean) and you want graphs which I doubt that tool can do. I wouldn't try it with it myself.

Hot cats are say 600C so cool within seconds to where they hardly do anything.

 

The numbers were changing all the time up down
But I can't do a graph.

Would a little hole in the exhaust affect the O2 sensors and or cat converter?

 

Also why would short term fuel trim Bank 1 sensor 2 not be available?

 

There isn't really one for either sensor 2.

The PCM is trying to fuel. It only knows roughly what is needed and has to learn the car's own differences due to wear, fuel variability etc.

It relies on a vital set of sensors including ECT, IAT, MAF, and so on. With the O2 sensor 1s. Those pesky things on your car don't do what any software guy would want so it has to swing the fuelling from wrong to wrong (rich to lean).

It looks at the sensor 1s to do that.

The sensor 2s are used to check the cats, mainly. (They also fine trim the sensor 1s on some cars, including the later jags and maybe the earlier ones as well but it's irrelevant here.)

You should have O2 readings for the 2s (downstreams) but they're not fuel trims. It would be sensible for them to be named HO2Sxxx or the like to show they're for the O2s but not fuel trims. That's how they're named on other OBD tools I've used.

Bear in mind you've got an incredibly sophisticated computerised control system you're diagnosing with a less clever but still amazing tool and it'll have some rough edges including maybe lying about that funny sensor 2 fuel trim.

 

darron, simple diagnostic test: Do you hear the cats rattle upon a dead cold start up? If yes, then failed converter on the side that rattles. Yes, an exhaust leak forward of the cats will set off codes, especially "Restricted Performance". More to come....

 

Cat deffo not rattling, had it on a ramp today at a exhaust shop. There was a small crack in the 1st silencer ( middle section of car) do that was pasted hopefully it will hold.

But the crack was after all the O2 sensors.

 

The crack after the cats are not the issue. Check the EGR and its pipe to the pass. exhaust manifold and all vaccume lines, etc.?

 

Are u still having issues?

 

Have you tried measuring pre and post cat temperatures when the engine has been run for a while?
Using an infra red non-contact thermometer should show the same pre to post cat difference for both cats. i.e. the post cat temperature should be up to 100°C hotter than the pre cat (temperature gradient) and they both should have about the same gradient.
Should be a simple point and read test that will tell you if your cat is shot within minutes.

Edit: I have the Mongoose and V131 software. I'll check if there are any catalyst test functions in the IDS software, amybe this will be of some help to you?