Freightliner Cascadia Trucks (CA125DC/CA125SLP) Service & Repair Manual

Electrical System and Main PDM Overview G02.01 Table of Contents System Overview Terms and Abbreviations .............................................................. 500 Electronic Power Distribution ........................................................... 501 Electrical Power Distribution ............................................................ 502 Powernet Distribution Box ............................................................. 503 Main Ground Junction Block (MGJB), Module 280 ........................................... 504 MEGA Fuse Junction Block (MFJB), Module 285 ............................................ 505 Powertrain PDM, Module 286 .......................................................... 506 Load Disconnect Switch, Module 293 .................................................... 507 Trailer PDM, Module 296 .............................................................. 508 PDM Diagram ...................................................................... 509 Components Component Locations ................................................................ 600 Component Details .................................................................. 601 Troubleshooting Possible Causes .................................................................... 700 Diagnostic Tools Required ............................................................. 701 Diagnosis .......................................................................... 702 PNDB Troubleshooting ................................................................ 703 SAM Cab and SAM Chassis Automatic Resetting Circuit Protection ............................. 704 Speciﬁcations SAM Chassis Fuses and Relays ........................................................ 800 SAM Cab Fuses and Relays ........................................................... 801 MFJB Fuses ....................................................................... 802 Powertrain PDM and Trailer PDM Fuses and Relays ......................................... 803 Primary PNDB Fuses and Functions ..................................................... 804 Cascadia Troubleshooting Manual, September 2012

Electrical System and Main PDM Overview G02.01 500 — Terms and Abbreviations Backbone—The main J1939 datalink wiring that lies between the two terminating resistors. It does not include the branch circuits to each ECU or to the diagnostic connector. CAN—Controller Area Network CAN ID—The identiﬁer for a speciﬁc message, which also contains the source address of the sending ECU communicating on the J1939 datalink. CGW—Central Gateway Communication Protocol—A set of rules governing communication between electronic devices. Datalink—A collection of wires, connecting system components, through which data is transmitted. Datalink Topology—The arrangement in which the nodes (ECUs) of a datalink are connected to each other. Diagnostic CAN—Datalink that runs from the diagnostic connector to the CGW. Diagnostic Connector—A 9-pin diagnostic connector is used for troubleshooting the electrical system. MFJB—MEGA ® Fuse Junction Block MGJB—Main Ground Junction Block SA—Source Address; indicates numeric assignment for a device that communicates on J1939. SAM—Signal Detect and Actuation Module SAM Cab—Signal Detect and Actuation Module Cab ("SAM Cabin"); this ECU controls mainly cab-related func- tionality. See G02.04 — SAM Cab for more information. SAM Chassis—Signal Detect and Actuation Module Chassis; this ECU controls mainly chassis-related function- ality. See G02.05 — SAM Chassis for more information. 501 — Electronic Power Distribution The multiplexed system contains the following power distribution components: • SAM Cab (relays and fuses), Module 32A • SAM Chassis (relays and fuses), Module 32K The SAM Cab and SAM Chassis are electronic control units (ECUs) that have power distribution components such as fuses and relays on them. Refer to G02.04 — SAM Cab and G02.05 — SAM Chassis for more information. The SAM Chassis and SAM Cab may use self-resetting circuit protection instead of fuses for some circuits. When the temperature of the SAM is above 170 F (77 C), it is in the tripped state. When it cools off, the circuit will again be energized. See 704 — SAM Cab and SAM Chassis Self-Resetting Circuit Protection. IMPORTANT: Do not change the self-resetting circuit breakers without using the special removal tool, located inside the cover of the SAM device. See Fig. 13. Failure to use the special tool could result in component damage. 502 — Electrical Power Distribution Standard electrical power distribution provides battery power to the electronics system, but it is not controlled by electronics. Cascadia Troubleshooting Manual, September 2012 G02.01/1

G02.01 Electrical System and Main PDM Overview The following modules are part of power distribution: • Main Ground Junction Block (MGJB), Module 280 • MEGA Fuse Junction Block (MFJB), Module 285 • Powertrain PDM, Module 286 • PNDB, Module 33P • Load Disconnect Switch, Module 293 • Trailer PDM, Module 296 503 — Powernet Distribution Box The powernet distribution box (PNDB) distributes and fuses battery power to many of the vehicle loads. An optional cab load disconnect switch (CLDS) is available to disconnect selected circuits. The CLDS may be located on the chassis near the battery box or mounted so that it is operated from inside the cab. There is an LED in the CLDS that will illuminate when power is on. The LED will ﬂash when certain faults are detected. Some vehicles have an auxiliary PNDB in addition to the primary PNDB. If the vehicle is equipped with a CLDS, it controls both. An additional LED status indicator is in the CLDS on dual PNDB systems. 504 — Main Ground Junction Block (MGJB), Module 280 The MGJB is a main node for connecting a returning ground to the battery. Many of the ground circuits previ- ously on the starter are now on the MGJB. 505 — MEGA Fuse Junction Block (MFJB), Module 285 The MFJB houses up to 5 MEGA fuses, and provides power to the engine harness, SAM Cab, SAM Chassis, chassis-mounted trailer PDM, and an inverter. The advantage of using an MFJB is that it provides increased robustness in the engine control and cab control electronic systems during cranking. This is because the cab electrical system is fed from the battery through the MFJB, and no longer from the starter. Separate starter cables provide both higher voltage levels and cleaner power during cranking. Additionally, there are improvements in circuit protection, and starter connection integrity (fewer circuits to con- nect at the starter stud). 506 — Powertrain PDM, Module 286 The Powertrain Power Distribution Module (PT-PDM) is dedicated to providing battery and ignition power to the engine (ECM), after treatment device (ATD), transmission (TCU), as well as other powertrain-related circuits. It is mounted in the engine compartment, above the quarter fender on the driver side of the vehicle. 507 — Load Disconnect Switch, Module 293 The load disconnect switch is used to disconnect (or open) the connection between the battery and the MFJB. Turning the load disconnect switch to the off position does not disconnect the batteries from the starter. NOTE: If the engine is running, turning the load disconnect switch to the OFF position will not shut off the engine. The powertrain PDM still gets battery voltage from the emergency power feed on the SAM system. Cascadia Troubleshooting Manual, September 2012 G02.01/2

Electrical System and Main PDM Overview G02.01 The load disconnect switch is mounted on one of three locations: • Inside the cab on the left side of the driver’s seat on a left-hand-drive vehicle. • On the battery box. • Outboard-mounted on the left frame rail. 508 — Trailer PDM, Module 296 The trailer PDM is used to supply trailer power to the chassis-mounted trailer receptacles. The SAM Chassis supplies control outputs to the remote trailer PDM. The trailer PDM is powered through the vehicle’s battery system. The SAM Chassis does not supply battery power to the trailer PDM. See Fig. 1. 509 — PDM Diagram MFJB MGJB Load Disconnect Switch Emergency Power Feed PT-PDM SAM Cab SAM Chassis Trailer PDM Inverter 04/24/2007 f545016 Fig. 1, PDM Diagram Cascadia Troubleshooting Manual, September 2012 G02.01/3

G02.01 Electrical System and Main PDM Overview 600 — Component Locations f001175a 02/27/2012 2 1 4 9 8 6 5 3 7 1. SAM Cab 2. Powertrain PDM (PT-PDM) 3. Powernet Distribution Box (PNDB) 4. SAM Chassis 5. Main Ground Junction Block (MGJB) 6. MEGA Fuse Junction Block (MFJB) 7. Cab Load Disconnect Switch (optional location) 8. Cab Load Disconnect Switch (optional location) 9. Trailer PDM Fig. 2, Component Locations Cascadia Troubleshooting Manual, September 2012 G02.01/4

Freightliner Cascadia Trucks (CA125DC/CA125SLP) Service & Repair Manual

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