5-6 months ago, we did a long trip to the Maze District in Canyonlands from SoCal in our 2001 Discovery 2 (200K miles). During the drive, the Check Engine Light came on and it was the Catalytic Converter Efficiency Code. I had the code reset about a month ago and after 400 miles it still hasn't completed the catalytic converter monitoring evaluation nor has the check engine light came on. Upon further inspection, I noticed the drivers side Y-pipe exhaust pipe has a crack near the exhaust manifold, (See pic) which I suspect cracked during the drive. You can clearly hear the exhaust leak when accelerating and occasionally smell exhaust fumes inside the car as well.

Could this crack be the cause for the system not being able to complete the monitoring of the Cats? I need the monitoring to be complete so that the Discovery 2 will pass SMOG in California. I found a local shop that can weld repair the cracked down pipe.

 

common failure point and anything upstream of the cats is going to wreak havoc on the ability to pass emissions

 

Definitely could be the cause. Mine cracked way worse there earlier this year, and yeah, welding it back up fixed a host of issues ranging from 02 codes to overall noise when driving. The sound of the disco went from sort of a 1970's chevy pickup to just a soft low V8 drone. Amazing what chaos a little crack can cause.

 

Same mine went this year as well, the disco runs better and a couple of random code have vanished

 

Thanks all for the feedback and confirms my hunch.

Another question regarding the Y-Pipes - as they are 20 yrs old now, am I better off just replacing the Y-Pipes and Cats with CARB compliant Cats (Appears DEC Catalytic Converters are CARB compliant, but pricy at $1500+), or try n weld-up the crack(s)? I was quoted $150-$200 to weld-repair the cracks, but if they will just continue to crack again, maybe better to just replace the pipes/CATs?? Welding of course will change the local metal properties of the pipes, but if experience has been the welds will hold, I'd rather go that course.

 

I got a new Magaflow downpipe and cat set for around $500... Deals are out there... even on CARB setups. Check with RV stores... That's where I found one at a decent price. See the model number in my signature... (not CA compliant.)

 

weld it up first and see if that's enough to get your passed. then go for weld-in carb compliant magnflow or generic. It'll definitely be cheaper than a whole new y pipe.

 

Have it welded. Bad design fault, cats hang below frame and if you high-center rover during off-roading...it rest on the cats and cracks the y-pipe flanges.