Harness Wire Identification
Caterpillar identifies different wires with eleven different solid colors. Table 1 lists the color codes of the wiring.
| Color Codes for Wiring | |
| Code | Color |
| BK | Black |
| BR | Brown |
| BU | Blue |
| GN | Green |
| GY | Gray |
| OR | Orange |
| PK | Pink |
| PU | Purple |
| RD | Red |
| WH | White |
| YL | Yellow |
In addition to the color, the entire length of each wire is stamped with a specific circuit number that is repeated on every 25 mm (1 inch) of the wire. The actual wires are identified on the schematic.
For example, a code of J011-RD on the schematic identifies a red wire that is stamped with the circuit number J011. This particular wire is the engine harness wire for the primary signal of the transformer in the number one cylinder. For all Caterpillar engine harnesses with electronic ignition systems, the code of J011-RD identifies the wire for the primary signal of the transformer in the number one cylinder.
The schematic also identifies the size of the wire. The size or gauge of the wire is called the American Wire Gauge (AWG). Unless the schematic specifies a different size, you may assume that the wire is 16 AWG.
Terminal Boxes
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| Illustration 1 | g00898814 |
There are two terminal boxes on the engine. (1) Terminal box for the master Electronic Control Module (ECM) (2) Terminal box for the slave ECM | |
Terminal Box for the Master ECM
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| Illustration 2 | g00985916 |
The connectors on the terminal box for the master ECM connect the master ECM to various engine controls, sensors, actuators, etc. (3) Emergency stop button (4) Service tool connector J23 for the Caterpillar Electronic Technician (ET) (5) Connector J16 for the actuators and for the fuel metering valve (6) Connector J15 is not used. (7) Connector J14 for the start command (8) Connector J13 for the gas shutoff valve (9) Connector J12 for the analog sensors (10) Connector J11 for the detonation sensors on the left side of the engine (11) Connector J10 for the speed/timing sensor, oxygen buffer, electrohydraulic actuator, and the compressor bypass valves (12) Wiring harness (13) Connector J19 for the wiring harness (14) Ignition harness for the left side of the engine (15) Connector J5 for the Integrated Temperature Sensing Module (ITSM) (16) Connector J8 for the wiring harness to the slave ECM (17) Connector J9 for use by the customer | |
Note: A 168-2028 Wiring Harness must be connected to the P19 connector in order for the engine to operate.
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| Illustration 3 | g00986278 |
Components inside the terminal box for the master ECM (18) Master ECM (19) Ground strap (20) Master ECM connector P1 (21) Master ECM connector P2 (22) P50 connector for calibration of the speed/timing sensor (23) 6 amp circuit breaker for the keyswitch circuit (24) 16 amp circuit breaker for the engine | |
Terminal Box for the Slave ECM
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| Illustration 4 | g00986142 |
Connectors on the terminal box for the slave ECM (25) Ignition harness for the right side of the engine (26) Connector J20 for the wiring harness to the master ECM (27) Connector J21 for the detonation sensors on the right side of the engine | |
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| Illustration 5 | g00986151 |
Components inside the terminal box for the slave ECM (28) Ground strap (29) Connector P4 for the slave ECM (30) Slave ECM (31) Connector P3 for the slave ECM | |