C-10, C-12, C-15 and C-16 Industrial Engines – Engine Wiring Information

The wiring schematics are revised periodically. The wiring schematics will change with updates to the harness wire. For the most current information, always check the revision number of the schematic. Use the schematic with the latest revision number.

Harness Wire Identification

Caterpillar identifies all wires with eleven solid colors. The circuit number is stamped on the wire at a 25 mm (1 inch) spacing. Table 1 lists the wire colors and the color codes.

Table 1
Color Codes for the Harness Wire    
Color Code     Color     Color Code     Color    
BK     Black     GN     Green    
BR     Brown     BU     Blue    
RD     Red     PU     Purple    
OR     Orange     GY     Gray    
YL     Yellow     WH     White    
        PK     Pink    

For example, a wire identification of A701-GY on the schematic would signify a gray wire with the circuit number A701. A701-GY identifies the power circuit for the No. 1 Injector solenoid.

Another wire identification on the schematic is the size of the wire. The size of the wire will follow the wire color. Wire size or gauge is referred to as AWG (Americal Wire Gauge). AWG is a description of the diameter of the wire.

For example, a code of 150-OR-14 on the schematic would indicate that the orange wire in circuit 150 is a 14 AWG wire.

If the gauge of the wire is not listed, the wire is 16 AWG.

Conversion of AWG Numbers to Metric Measurements

Table 2 shows the various AWG numbers that are used for the wires. The metric equivalent for the diameter of each AWG number are also shown.

Table 2
Metric Equivalents for AWG Numbers    
AWG Number     Diameter (mm)     AWG Number     Diameter (mm)    
20     0.8     14     1.6    
18     1.0     12     2.0    
16     1.3     4     3.2    

Welding on a Machine that is Equipped with an Electronic Engine Control System

Proper welding procedures are necessary in order to avoid damage to the engine’s electronic control module, sensors, and associated components. The component that requires welding should be removed. When welding on a machine that is equipped with an electronic engine control system 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.

  1. Stop the engine. Turn the keyswitch to the OFF position.
  1. Disconnect the negative battery cable from the battery. If a battery disconnect switch is installed, open the switch.

    Illustration 1 g01100101

    The welding current will not cause damage to any of the associated components.

  1. 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.
  1. Protect the wiring harness from welding debris and from spatter.
  1. Weld the materials by using standard welding methods.