French engineer Eugene Houdry was a racing enthusiast who became an American citizen during World War II. In the US, Houdry developed the first catalytic conversion processes, which produced high octane gasoline for the US and Allied air forces. In the 1950's, Houdry became concerned with the effect of car pollution on the human body in Los Angeles and invented the automobile catalytic converter, which went into service in 1975.
The modern 3-way catalytic converter reduces nitrogen oxides, hydrocarbons and poisonous carbon monoxide from your JK Wrangler's exhaust. The 3.8-L EGH (2007-2011) engine uses four cats and the 3.6-L Pentastar (2012-present) uses two cats. The Mopar 5-year, 10,000-mile warranty, starting in 2010, covers the engine, transmission and drive system only. Warranty protection for your emissions system is separate from your Mopar warranty: federally mandated emissions warranties cover your catalytic converters, engine control module (ECM) and On-board Diagnostic (OBD-2) for 8 years/80,000 miles.
This DIY will mainly cover the 2007 to 2011 cat system, as it is more likely out of warranty protection. The current Mopar part number for the cat assembly is 52059930AH, which replaces 52059930AG and 52059930AF.
Figure 1. 3.8L catalytic converter assembly.
For reference, in 2012, Mopar introduced the Pentastar engine, which incorporates integral exhaust manifolds as part of the engine block. The Pentastar uses only two cats, which are replaced as individual units and bolt directly to the block. The left cat is Mopar part 68085148AG, and the right cat is 68085119AC.
Figure 2. 3.6L Pentastar catalytic converters.
Important Note
To insure the parts are correct, always order parts by your specific Vehicle Identification Number (VIN).
Materials Needed
As shown in Figure 1, the catalytic converter is large and the down-pipe portion is 20" tall. You will need about 20" minimum clearance underneath the Jeep to tilt and work the cat assembly out from under it. If needed, raise the Wrangler on drive-on ramps or jack stands. The outboard part of the axle tubes are the factory support points, as shown in the example in Figure 3.
Figure 3. Jacking and jack stands.
Pro Tip
Do not go under a raised vehicle unless you are certain it is secure.
Step 2 – Disconnect the negative battery cable
For safety, disconnect the negative (black) battery cable from the battery.
Figure 4. Disconnect negative battery cable.
Step 3 – Remove any skid plates or crossmembers (as needed)
Figure 5. Skid plate and crossmember removal.
Step 4 – Remove exhaust manifold heat shields
Figure 6. Exhaust manifold heat shields.
Step 5 – Remove oxygen sensors
The two upstream cats are monitored by oxygen sensors, with one sensor above and below each upstream cat.
Figure 7. Oxygen sensors.
Step 6 – Remove upper flange bolts
Figure 8. Catalytic converter to exhaust manifold.
Pro Tip
Use only an electric heat gun on the exhaust bolts, as the open flame of a torch is very hazardous when working near a gasoline engine.
Step 7 – Loosen lower clamp and remove catalytic converter
Figure 9. Catalytic converter to exhaust pipe clamp.
Step 8 – Install new catalytic converter assembly
The modern 3-way catalytic converter reduces nitrogen oxides, hydrocarbons and poisonous carbon monoxide from your JK Wrangler's exhaust. The 3.8-L EGH (2007-2011) engine uses four cats and the 3.6-L Pentastar (2012-present) uses two cats. The Mopar 5-year, 10,000-mile warranty, starting in 2010, covers the engine, transmission and drive system only. Warranty protection for your emissions system is separate from your Mopar warranty: federally mandated emissions warranties cover your catalytic converters, engine control module (ECM) and On-board Diagnostic (OBD-2) for 8 years/80,000 miles.
This DIY will mainly cover the 2007 to 2011 cat system, as it is more likely out of warranty protection. The current Mopar part number for the cat assembly is 52059930AH, which replaces 52059930AG and 52059930AF.
Figure 1. 3.8L catalytic converter assembly.
For reference, in 2012, Mopar introduced the Pentastar engine, which incorporates integral exhaust manifolds as part of the engine block. The Pentastar uses only two cats, which are replaced as individual units and bolt directly to the block. The left cat is Mopar part 68085148AG, and the right cat is 68085119AC.
Figure 2. 3.6L Pentastar catalytic converters.
Important Note
To insure the parts are correct, always order parts by your specific Vehicle Identification Number (VIN).
Materials Needed
- Catalytic converter assembly
- Flange bolts and nuts
- Exhaust clamp
- Exhaust sealant
- 2 upstream oxygen sensors (if needed)
- 2 downstream oxygen sensors (if needed)
- 22mm (7/8") oxygen sensor wrench
- Socket wrench set
- PB Blaster
- Heat gun
- Mechanic's gloves
- 48" x 48" sheet of scrap cardboard.
As shown in Figure 1, the catalytic converter is large and the down-pipe portion is 20" tall. You will need about 20" minimum clearance underneath the Jeep to tilt and work the cat assembly out from under it. If needed, raise the Wrangler on drive-on ramps or jack stands. The outboard part of the axle tubes are the factory support points, as shown in the example in Figure 3.
Figure 3. Jacking and jack stands.
Pro Tip
Do not go under a raised vehicle unless you are certain it is secure.
Step 2 – Disconnect the negative battery cable
For safety, disconnect the negative (black) battery cable from the battery.
- Write down any radio or navigation security codes.
- Use a 10mm wrench to remove the negative battery cable.
- Ensure the negative cable cannot contact the negative or positive terminals.
Figure 4. Disconnect negative battery cable.
Step 3 – Remove any skid plates or crossmembers (as needed)
- Wranglers may have a variety of aftermarket skid plates over the engine and transmission areas. Remove yours as needed.
- The OEM crossmember should not be in your way, but it can be removed with a few bolts if you find it helpful to do so.
- An assistant may be helpful, as the pieces can be heavy.
Figure 5. Skid plate and crossmember removal.
Step 4 – Remove exhaust manifold heat shields
- Use the 10mm wrench to remove the lower nut and two upper bolts on the left-side heat shield.
- Remove the heat shield. It has two pieces, as shown.
- Repeat on the right-side heat shield.
Figure 6. Exhaust manifold heat shields.
Step 5 – Remove oxygen sensors
The two upstream cats are monitored by oxygen sensors, with one sensor above and below each upstream cat.
- Disconnect the electrical plugs on all four oxygen sensors.
- Use the 22mm (7/8") oxygen sensor wrench to remove each sensor.
Figure 7. Oxygen sensors.
Step 6 – Remove upper flange bolts
- Spray the flange bolts with PB Blaster and allow time to soak.
- Apply heat to the flange bolts with the electric heat gun.
- Have an assistant support the cat assembly from below, or prop it on something. Remember that the assembly weighs 24 pounds.
- Use the 15mm wrench to remove the upper flange bolts and lock nuts.
Figure 8. Catalytic converter to exhaust manifold.
Pro Tip
Use only an electric heat gun on the exhaust bolts, as the open flame of a torch is very hazardous when working near a gasoline engine.
Step 7 – Loosen lower clamp and remove catalytic converter
- Use the 15mm wrench to loosen the lower clamp to the exhaust pipe.
- Support the cat assembly and slide it out of the exhaust pipe.
- Unhook any exhaust hangers, lower the cat assembly, and remove it.
Figure 9. Catalytic converter to exhaust pipe clamp.
Step 8 – Install new catalytic converter assembly
- Position the new cat assembly on the sheet of cardboard, so it can be moved without scratching.
- Slide the cat under the Wrangler and fit it into the exhaust pipe. Use exhaust sealant and a new clamp, but don't tighten it.
- Have an assistant support the cat, install the upper flange bolts and lock nuts, then tighten them.
- Hook-up any exhaust hangers and tighten the lower exhaust pipe clamp.
- Install the new upstream and downstream oxygen sensors, then connect the electrical plugs.
- Reinstall any skid plates or crossmembers that were removed.
- Reinstall the exhaust manifold heat shields.
- Attach the negative battery cable.
- Run the engine and check for exhaust leaks.
