Sports Cat problem ?

[2700gavin]

I have a Galant sport 2.0L with a cobra SS exhaust, I have also a sports CAT fitted. Occasionally the Engine Management light comes one , the alarm failure is "P0240 Catalyst System Efficiency below threshold bank 1". When I had the cat fitted I was warned that this alarm may occur but have not come across them on Galant VR4's but occurs all the time on Scoobies. The exhaust manufacturer guarantees the exhaust will pass emissions but also /help said that you can sometimes get piggy back sensors to fool the lambda sensor on the exhaust. Is this true if so does anybody know where to get one from or do I just put up with the orange light on ? http://www.clubvr4.com/forum/images/smilies/help.gif.
PS think the website is great and am going to become full member shortly.

[Kieran]

Yeah, the sports are to OBD2 standard, meaning there's an 02 sensor each side of the Cat. One checks the efficiency of the other - As you say, it's a pretty common thing. The reason it doesn't happen on VR4s is because they only have on o2 sensor and are therefore not OBD2 compliant.

Can you confirm the Diag code? Are you sure it's not P0420? I can't see a 240 in my books here.

Assuming it is P0420 then yes, it's no doubt because you've got a sports cat on there that's not removing enough crap. Best suggestion is to see how it's fixed on scoobies. If it's something like a piggyback that clamps the o2 signal, then that might work on your car. If it's something like an ECU reprogram then it's unlikely that you can cure it.

[Paul C]

if you remove the second sensor and leave it connected.would this fool the ecu that the exhaust gas is clean enough.

[Turbo_Steve]

Actually, I would imagine that the easiest fix is to common the two lamda inputs at the ECU end, so it only reads one sensor. It's only a volt meter after all, and they should be sharing the same grounding plane.

[bradc]

I like paul's idea :) It'd only be capable of sensing the dirty air in England....actually that mightn't be such a good idea after all :D

[Kieran]

Actually, I would imagine that the easiest fix is to common the two lamda inputs at the ECU end, so it only reads one sensor. It's only a volt meter after all, and they should be sharing the same grounding plane.

Now that sounds like a plan!

[Paul C]

Does it need to see a true exhaust reading before the cat and a reduction after. So if you common the dirty side it wont see a low enough figure, but if you common the clean side will it run like a bag or crap at idle.

[2700gavin]

I think I'll try removing the sensor and will report back how it goes.

[miller]

All we ever did on GTO's was tape the two sensor wires together and push them up into the floor pan out of the way.

Did this on mine and never had the cat light on once.

Though then again as i must realise these cars are newer and should have better systems/pan /pan

Mike