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Old 11-29-2011, 05:43 PM
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drivinfaster drivinfaster is offline
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Location: in the sticks you piney
Join Date: Nov 2007
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i did emission testing, ase master tech with L1 and X1 catagories, so regardless of the vehicle, all cats can be tested for o2 retention and hc/co reduction prior to replacement to verify they are malfunctioning. a competant shop will be able to do these tests properly.

not sure of the mileage, but if past the 80k mark you most likely do need cats. i've had a few cases where the code popped up and the shop where i worked was simply throwing cats at the car (apparently this was fine when at a dealership under 'warranty'....) but then when a 'cash' repair came back with the exact same code after a cat was thrown at it is when i was called in to take a look.

it had new o2 sensors as well, but the culprit wasn't the cat, or the sensors, but rather the wiring from one of the rear o2 sensors rubbing against the chassis. if the cat had been properly checked with a gas analyser it would have been verified that the cat was bad. as it stood, i could not verify the previous cat condition, so to not throw the other tech under the bus (much) i stated that the harness must have been jarred loose and rubbed through the insulation causing the fault to manifest.

the cats listed in the link, however, are not 'universal'. those would be a direct replacement as it has the manifold as part of the assembly. a 'universal' unit would only have a few inches of inlet and outlet pipe to it, requiring cutting and welding to fit. it also would increase the potential for the unit to be put in backwards. (yes, they are directional, dual bed 3 way convertors, as are most all cats now).

you could check the freeze frame data for the code to see if it is consistent each time the fault pops up, but i think that most likely you will be needing to replace the cat. and, although i do not own an e39, it's quite possible the other bank will not be very far behind. (again, flying blind here without history and mileage, just my own experience in repairs)

hope this helps.

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