What are the rules for replacing catalytic
In a closed loop emissions operation, pump
air is injected downstream between reduction and oxidation catalysts
when the engine is warm.
Three-way catalytic converters contain both
catalysts in a single housing, with an air inlet between the two converters.
Original equipment converters on new cars
and light trucks are currently covered by an eight year/80,000 mile
emissions warranty. Motorists can return to the new car dealer for free
replacement as long as the converter is covered.
The customer can choose to have an independent
repair garage replace the converter at his own expense if it is still
under warranty. Once the vehicle is out of warranty, he pays to have
it fixed no matter where he takes it.
The converter should go at least 100,000
miles on most late model vehicles. Trouble is rare unless the converter
has been lead fouled (by using leaded gasoline), damaged by overheating
(often due to unburned fuel in the exhaust from a misfiring spark plug
or leaky exhaust valve), or removed.
Removing the converter and replacing it with
a straight pipe is not permissible. The new Clean Air Acts make anyone
(including the motorist himself) liable for a $2,500 fine if they remove,
disconnect or render inoperative any emission control device.
If the vehicle has flunked an emissions test
and the cause is determined to be a bad converter, or if the converter
is clogged, damaged, lead-fouled, rusted out, physically damaged or
missing, it is okay to replace it. Federal law prohibits aftermarket
garages from replacing converters as long as they're under the five/50
emissions warranty, unless any of the previously-mentioned reasons exist
The shop must first document the reasons,
along with the vehicle's odometer reading, and have the customer sign
it before the converter is replaced. The shop must keep the old converter
for 15 days and the paperwork for six months. The replacement converter
must be the same type as the original (two-way, three-way or three-way
plus oxygen), be EPA-certified, and be installed in the same location
as the original.
Aftermarket replacement converters meeting
EPA requirements must have a minimum lifespan of 25,000 miles, and include
a five year/50,000 mile warranty covering exterior shell and welded
pipes against defects in materials and workmanship.
Used converters are no longer allowed unless
the supplier can certify the converter is still capable of cleaning
up 50% of the unburned hydrocarbon (HC) and carbon monoxide (CO) emissions
within two minutes of start-up, and 75% of the HC and CO emissions within
All approved replacement converters are required
to carry a permanent label that identifies the type of converter (N
for new, U for used), a code number issued to the manufacturer by the
EPA, an application part number, and a manufacturing date.