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How to Install a Catalytic Converter in a GMC Sonoma

Depending on what year and what motor you have in your GMC Sonoma will dictate the level of difficulty and the type of catalytic converter you need for replacement. Before the year 2000, the converter was connected to the exhaust system behind the front exhaust pipe in the popular 4.3 liter engine. In the year 2000, the catalytic converter became the front exhaust pipe which is much more challenging and difficult to remove and replace.

Instructions

How to Install a Catalytic Converter in a GMC Sonoma

1

Lift the GMC Sonoma all the up on the car lift. Load all the tools and the new converter into the tool cart/tray and wheel it over near you under the Sonoma, but out of your way. Put on the safety glasses.

2

Locate and remove the oxygen sensors. In the front Y-pipe converter application, there will be three oxygen sensors. In the older kind of Sonoma, there is only one oxygen sensor. Locate the plugs for the wire and unplug them using the flathead screwdriver to press in on the clip lock. Use the ratchet and oxygen sensor socket to remove the sensors. If need be, you may have to heat the pipe up a little with the torch to extract them. Allow them to cool down if you needed the torch.

3

Screw the oxygen sensor(s) into the new converter, but apply a light coat of anti-seize lubricant on the threads first. For the Y-pipe with three sensors, make sure to put the correct sensor into the correct port. Be caul not to overtighten to prevent stripping out the threads of the sensor(s).

4

Light the torch with the striker and heat up one nut on the manifold stud at a time (for the front Y-pipe converter). When the nut is cherry red, place the pneumatic gun, extension, swivel and socket onto it and remove the nut. If the converter is connected to the front pipe, cut the three nuts and bolts with the torch on both sides of the flange, then use the hammer and punch to knock the rest of the bolt out of the flange connection.

5

Cut the two or three nuts and bolts out of the rear flange connection on the converter using the torch. Cut the bolt on both sides of the flange and knock the rest of the bolt from the flange connection using the hammer and a punch. Be caul on the last bolt as the converter will separate from the exhaust system. Put on the gloves and remove the old converter.

6

Install the new catalytic converter starting with the inlet first (closest to the motor). Install the gasket(s) first and then thread on new manifold stud bolts for the Y-pipe converter or replace the nuts and bolts on the converter connected to the front pipe. Use a bolt head and washer on one side and a lock washer and nut on the other side of the flange.

7

Tighten the nuts on the manifold with the gun or tighten the nuts and bolts on the flange connection, using the gun on one side and holding the bolt steady with a hand wrench on the other.

8

Replace the gasket and hardware on the rear connection of the catalytic converter. Place the bolt head and flat washer on one side and the lock washer and nut on the other side of the flange connection. Tighten with the gun on the nut side and hold the bolt head with a hand wrench.

9

Plug the oxygen sensor wire(s) back into the plug(s).

10

Remove the tool cart and any other debris from under the Sonoma, lower the truck and start the engine up. Raise it back up and check for any possible exhaust leaks coming from the manifold, flange or oxygen sensor connections. Tighten as needed.