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How to Change the Catalytic Converter on a 2004 Chevy TrailBlazer

The 2004 Chevy Trailblazer base model came with a 4.2-liter inline six-cylinder engine and a four-speed automatic transmission. Your catalytic converter is located between the exhaust manifold and the muffler. A faulty catalytic converter can result in poor performance and higher emissions levels that will cause you to fail an emissions test. Replacing your catalytic converter is a straightforward task, but the transmission mount has to be removed because of the length of the catalytic converter assembly.

Instructions

Removal

1

Park the vehicle on a level surface and set the parking brake. Lift the front of the vehicle into the air with a floor jack and place jack stands under the front frame rails. Lower the vehicle until it rests securely on the jack stands. Allow the engine and exhaust to cool completely before continuing.

2

Position yourself under the vehicle so that you can clearly view the catalytic converter and its connection to the exhaust manifold. Locate the front oxygen sensor that is positioned just after the first flange and disconnect the pigtail from the wiring harness. Follow the catalytic converter piping after the converter to find the rear oxygen sensor. Disconnect the rear oxygen sensor pigtail from the wiring harness.

3

Place the oxygen sensor socket over the front oxygen sensor so that the pig tail extends through the slotted portion of the socket. Rotate the sensor counterclockwise with a ratchet to remove the sensor from the exhaust. Apply heat with a propane torch around the base of the sensor, if it is difficult to remove. Repeat for the rear oxygen sensor and label each one accordingly; they are not interchangeable and must be installed in the same position.

4

Place one jack stand at the rear and one under the front of the converter assembly, and elevate them until they make contact with the converter assembly. Remove the nuts securing the converter assembly to the exhaust manifold with a ratchet and socket. Remove the nuts securing the converter assembly to the rear muffler pipe.

5

Place a floor jack under the transmission and place a small block of wood on the jack arm. Raise the jack until the wood makes contact with the case of the transmission, but do not apply any upward force. Examine the transmission support that runs between the two frame rails to find the two center access holes. Remove the bolts securing the transmission mount to the transmission support with a socket and ratchet.

6

Remove the bolts securing the transmission support to the frame rails. Lower the transmission support from the vehicle and set it aside. Remove the bolts securing the transmission mount to the base of the transmission. Remove the catalytic converter and transmission mount from under the vehicle.

7

Pry the rubber hangers from the old catalytic converter assembly with a pry bar and set them aside. Set the transmission mount aside, with the rubber hangers attached.

Installation

8

Examine the rubber hangers for any damage or wear and replace as necessary. Install the transmission mount, with the rubber hanger bracket attached, to the transmission. Install the mounting bolts and tighten to 48 foot-pounds with a torque wrench.

9

Set the catalytic converter assembly onto the jack stands so that the flanges at both ends meet up with the exhaust manifold and muffler assembly. Lift the catalytic converter assembly as necessary and install the rubber hangers at the transmission mount to the metal hangers on the converter assembly.

10

Lift the transmission support into place between the frame rails and install the retaining bolts. Install the transmission mount to transmission support nuts through the access holes and tighten to 35 foot-pounds.

11

Install a new gasket at the front and rear of the converter assembly. Slide the converter assembly rear flange over the studs for the muffler pipe. Install the rear mounting nuts hand tight. Install the front converter flange to the exhaust manifold and install the mounting nuts hand tight. Tighten the mounting nuts for both flanges one turn at a time until they are tightened to 33 foot-pounds.

12

Remove the jack stands from under the converter assembly. Clean the oxygen sensor threads with a wire brush and apply copper anti-seize to the threads. Install the both oxygen sensors to the converter assembly until hand tight. Tighten both sensors to 30 foot-pounds with a torque wrench and oxygen sensor socket. Plug the oxygen sensor pigtails to their respective wire harness connectors.

13

Lift the front of the vehicle off the jack stands and remove the jack stands from under the vehicle. Lower the vehicle to the ground and remove the floor jack.

Posted by Unknown at 10:00 AM

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Labels: 2004, a, catalytic, change, chevy, converter, how, on, the, to, trailblazer