GM 19418958
Catalytic Converter

Begin by raising the 1500 series vehicle through proper support before the Catalytic Converter replacement process can begin. Start work by removing the bolts from the oil pan skid plate and skid plate (if present) then disconnect the transmission crossmember. First disconnect the right front heated Oxygen Sensor (HO2S) electrical connector then remove the right front connector position assurance (CPA) retainer. Unplug the electrical connector of right rear ho2s before removing its cpa retainer. Repeat this process on the left rear ho2s. Vehicles with 4l60-e/4l70-e automatic transmissions need the left front ho2s electrical connector removed and its corresponding cpa retainer detached. Vehicles which have regular production options (RPOs) lc9/lmg/ly5/l76/ly2 require removal of Muffler to Catalytic Converter nuts. Rpo l92 calls for Muffler to Catalytic Converter nuts to be taken out. Lift out the ho2s and Catalytic Converter to Exhaust Manifold nuts before pulling the Catalytic Converter assembly free from exhaust manifolds and exhaust Muffler. When needing to replace the Catalytic Converter assembly you must remove both exhaust seals and the ho2s from the assembly. The installation includes application of gm p/n 12377953 anti-seize compound to ho2s threads before mounting to the Catalytic Converter assembly and torqueing at 42 n.m (31 lb ft). After installing new exhaust seals on the manifolds and Muffler, fasten the Catalytic Converter assembly to its positions while tightening nuts to 50 n.m (37 lb ft). When installing the ho2s on vehicles with rpo l92 begin by tightening the Catalytic Converter to Muffler nuts to 45 n.m (33 lb ft). Rpos lc9/lmg/ly5/l76/ly2 require installation of Catalytic Converter to Muffler nuts with a torque of 45 n.m (33 lb ft). The installation process includes reconnecting electrical connectors for the ho2s followed by retainer installation. After finishing, position the oil pan skid plate then fasten the bolts to 28 n.m (21 lb ft) and carefully lower the vehicle.

The initial step to replace the left side Catalytic Converter in a 2500 series vehicle involves elevating and stabilizing the vehicle. Remove the skid plate following the order of unscrewing rear oil pan skid plate bolts and taking off 2 front oil pan skid plate bolts if your vehicle has this equipment component. Remove the Muffler. The procedure starts with removal of the left front connector position assurance (CPA) retainer followed by separation between the left front heated Oxygen Sensor (HO2S) electrical connector and engine wiring harness before removing the left rear cpa retainer. Use a screwdriver to remove the left rear ho2s electrical connector which connects to the engine wiring harness and then unscrew the Catalytic Converter to Exhaust Manifold nuts to separate the Catalytic Converter from the Exhaust Manifold studs. Catalytic Converter hanger should be extracted out of its position within the hanger bracket. Plan to replace the Catalytic Converter. Remove both the exhaust seal and utility Oxygen Sensor components first. Before installing a new Catalytic Converter assembly, apply anti-seize compound gm p/n 12377953 or similar equivalent to the threads of the old sensors. Secure the ho2s sensors on the Catalytic Converter assembly with a torque of 42 n.m (31 lb ft). Position the hanger bracket inside the new exhaust seal before inserting the Catalytic Converter hanger through the hole. Attach the converter to the Exhaust Manifold studs while applying 50 n.m (37 lb ft) torque to the mounting nuts. The left rear ho2s electrical connector needs to be wired to the engine harness while the left rear cpa retainer needs to be installed before wiring the left front ho2s electrical connector to the engine harness for left front cpa retainer installation. Complete the installation by positioning the oil pan skid plate followed by tightening the 2 rear bolts to a secure fit then install the 2 front bolts only when equipped to a torque of 28 n.m (21 lb ft). Finally lower the vehicle.

Remove the exhaust seal and the HO2S's.

Remove the right rear CPA retainer and disconnect the engine wiring harness electrical connector from the right rear HO2S electrical connector.

Install the heated oxygen (HO2S) sensors.

Remove the transmission crossmember.