BASE AS 1779778 - Caterpillar

Proper welding procedures are necessary in order to avoid damage to the engine's electronic control module, to sensors, and to associated components. Remove the component that requires welding. When welding on a engine that is equipped with an Electronic Control Module (ECM) and removal of the component is not possible, the following procedure must be followed. This procedure provides the minimum amount of risk to the electronic components.
Do not ground the welder to electrical components such as the ECM or sensors. Improper grounding can cause damage to the drive train bearings, hydraulic components, electrical components, and other components.Clamp the ground cable from the welder to the component that will be welded. Place the clamp as close as possible to the weld. This will help reduce the possibility of damage.
Stop the engine. Remove the electrical power from the ECM.
Disconnect the negative battery cable from the battery. If a battery disconnect switch is installed, open the switch.
Illustration 1 g01143634
Service welding guide (typical diagram)
Connect the welding ground cable as close as possible to the area that will be welded. Components which may be damaged by welding include bearings, hydraulic components, and electrical/electronic components.
Protect the wiring harness from welding debris and from spatter.
Weld the materials by using standard welding methods.