GM 19418932
Catalytic Converter

To replace the Catalytic Converter on the left part of the 2500-series, first, do not forget to raise and hold the vehicle. Unfasten 2 rear oil pan skid plate bolts, remove 2 front oil pan skid plate bolts, and remove the skid plate if present. Next, remove the Muffler. Remove the left front connector position assurance (CPA) retainer and loosen the left front heated Oxygen Sensor (HO2S) electrical plug from the engine wiring harness. Remove the left rear cpa retainer, disconnecting the left rear ho2s. After that, take out the Catalytic Converter nuts to Exhaust Manifold and disengage the Catalytic Converter from the Exhaust Manifold studs. Pull the hanger of the Catalytic Converter from its hanger slot. Here if replacing the Catalytic Converter remove driver and ho2s's by breaking their seal in the exhaust. During installation, in case of old sensors, the threads must be coated with an anti-seize compound gm p/n 12377953 or equivalent. Mount the ho2s's to the Catalytic Converter assembly tightening the sensors to 42 n.m (31 lb ft). Mount the new exhaust seal, as necessary, slide the Catalytic Converter hanger into the hanger bracket, and mount the Catalytic Converter to the studs of the Exhaust Manifold. Tighten nuts to 50 n.m (37 lb ft). Connect left rear ho2s electrical connector, install left rear cpa retainer. At this point, make the connection between the left front ho2s electric connector and install the left front cpa retainer. Reinstall the Muffler, position the skid plate of oil pan, and attach the 2 rear oil pan skid plate bolts tightly followed by installing the 2 front oil pan skid plate bolts if necessary, by tightly tightening them to 28 n.m (21 lb ft). Finally, lower the vehicle.

The process of replacing the right-side Catalytic Converter on the 2500 series starts with hoisting the vehicle into a proper position for access. First loosen the 2 rear oil pan skid plate bolts then remove the 2 front oil pad skid plate bolts before taking off the skid plate if your vehicle has this component. The next step involves taking out both the Muffler and the transmission crossmember. Remove the right front connector position assurance (CPA) retainer and disconnect the right front heated Oxygen Sensor (HO2S) electrical connector that connects to the engine wiring harness electrical connector. Separate the right rear cpa retainer before unconnecting the engine wiring harness electrical connector from the right rear ho2s electrical connector. Before separating the Catalytic Converter from Exhaust Manifold studs cut its engine harness clip electrical connector clip and remove Catalytic Converter to Exhaust Manifold nuts. Pull the Catalytic Converter hanger out of its position in the hanger bracket. Before installing a new Catalytic Converter remove any needed exhaust seal and extract both ho2s sensors (2 and 3). Before installing the Catalytic Converter with any previous sensors apply gm p/n 12377953 anti-seize compound or equivalent product to the threads. Put the ho2s's (2 and 3) on the Catalytic Converter assembly where you should torque each sensor to 42 n.m (31 lb ft). Insert the new exhaust seal before you guide the Catalytic Converter hanger into its bracket and then install the Catalytic Converter onto Exhaust Manifold studs. Tighten Exhaust Manifold nuts holding the Catalytic Converter in position at 50 n.m (37 lb ft). Reinstall the right rear ho2s electrical connector clip to the engine harness clip then join the engine wiring harness electrical connector with the right rear ho2s electrical connector and slot in the right rear cpa retainer. The right front ho2s electrical connector requires connection to the engine wiring harness electrical connector while you install the right front cpa retainer. Complete the installation by putting the Muffler back in place while also repositioning the transmission crossmember and oil pan skid plate and tighten the two rear pan bolts until they are snug before securing the two front pan bolts if the vehicle has them. Torque these front bolts to 28 n.m (21 lb ft).

Raise and support the vehicle.

For 1500 series, remove the catalytic converter to muffler nuts; for 2500/3500 series, remove the muffler to catalytic converter nuts.

Raise and support the vehicle.

Remove the oil pan skid plate bolts and skid plate if equipped, followed by the transmission crossmember.

Remove the catalytic converter to exhaust manifold nuts and separate the catalytic converter from the exhaust manifold studs.

Install new exhaust manifold seals (2 and 3).