$49.95 head pipe catalytic converter replacement on 2001 4.0 - Fixed my P0432 code
My 2001 4.0L TJ was throwing out the P0432 code- Catalyst System Low Efficiency Bank 2. Thanks to the incredibly wicked awesome $4.95 Torque Pro OBDII Android app and a wireless bluetooth OBDII code scanner, I discovered that the pre and post O2 sensors were returning basically identical voltages, indicating that the catalytic converter had no effect on the exhaust passing through it.
Since both O2 sensors passed testing, I was confident the problem had to be the catalytic converter. Rather than spend $300+ on a replacement head pipe, I thought I'd risk $49.95 and try to "cut and paste" in a universal cat. I used a "Thunderbolt Universal Catalytic Converter 2" OBD II Compliant..." I found on ebay (the link takes you to the seller's store). It was the shortest one I found and reasonably priced.
To assure that the head pipe would line up with the exhaust header after welding in the new cat, I used a jig. I made two steel plates with holes drilled on 3.5" centers, bolted them to each flange and then joined the plates with a third section. So when I cut out the bad kitty, the flange hasn't moved from it's original position.
The photo below shows the bad cat removed and the flange "floating" in it's original position.
The new and the old converters.
After determining how to align the new converter to the head pipe, I shortened it at each end so that it was about 1/2" longer than the old section I cut out (sorry, no photo.) I then made cuts into the ends with a band saw to create tabs, and bent them inward with pliers to fit the top and bottom diameters of the head pipe. Bending in the tabs reduced the overall length of the new cat, which is why I added the extra 1/2" in length. The result was just enough overlap of old pipe to accommodate the welds.
Top and bottom fit after sliding the new converter into place.
Welded in and ready to install.
The flanges lined up perfectly to the exhaust manifold, the P0432 code didn't return and I passed the emissions test the following day!
When I bought the Jeep in 2011, the P0432 was part of the reason the previous owner was selling it. A dealer had told him that all 3 cats needed to be replaced at a cost of over $2,400.00. It's such a shame.
Thanks... the only concern that comes up is flow... is there a difference? HMMMMM....
I think the body diameter of the converters are the same size, and they just taper down to the different O.D's. Because you will be cutting all the pipe off and a bit into the tapered sections, the result will be an opening larger than the outlet diameter and your head pipe diameter, no matter what the O.D. was of the cat you purchased.
After writing this, I'm now remember thinking the 2" O.D. might have been a better choice because of how large the outlet was after trimming the cat. I think there would have been a little less work tapering the trimmed cat down to the 2.25" O.D. head pipe, because the trimmed outlet size would have been smaller and closer to the head pipe diameter.
Makes sense... I was thinkin along that line... just considering a flow factor. I am wondering if the the only difference in flow rate is the ID of the inlet and outlet. If that is the case, there would be no harm in getting the 2" OD and working from there.
~Todd~ 2004 X 4.0 5 speed---SOLD
4" Lift, 4.56's, 33" Duratracs on M/T Classics
RR SYE, Tatton CV, MML, BL, TT, Dynomax Exhaust
Hella Lighting: Driving, Fogs and H4 E-Codes NOPE! ... and NEVER will be...