2015 Peterbilt 389 Fuse Box Diagram & Amperage

Quick Answer

The 2015 Peterbilt 389 typically features three primary fuse box locations:

• Under-Hood Power Distribution Center: Located on the passenger side, usually near the firewall or battery box.
• Interior Fuse Panel (Dash Kick-Panel): Often found behind a removable panel on the passenger side kick panel or dashboard.
• Cab/Sleeper Fuse Panel: If equipped with a sleeper, an additional fuse panel may be located within the sleeper compartment, usually in a cabinet or under the bunk.

Under-Hood Power Distribution Center

The under-hood power distribution center is the main hub for high-current circuits and relays, protecting critical systems like the engine control module (ECM), fuel pump, headlights, and ABS. Always verify the fuse legend on the inside of the fuse box cover for your specific truck's configuration, as variations can exist based on engine type and installed options.

Relays for critical systems like the starter, ignition, and high/low beam headlights are also typically found in this location. Refer to the fuse box cover for precise relay identification.

Interior Fuse Panel (Dash Kick-Panel)

This panel primarily houses fuses for interior accessories, cabin lighting, and various control modules. Its exact location can vary, but it's commonly found behind a removable panel on the passenger side kick panel or within the center dashboard area.

Cab/Sleeper Fuse Panel (If Equipped)

For 389 models equipped with a sleeper, an additional fuse panel supplies power to sleeper-specific amenities. This panel is generally located in a cabinet within the sleeper, often under the bunk or in a side wall compartment. Always consult your owner's manual or the fuse box cover for the precise layout.

How to Test a Fuse

Testing a fuse is a straightforward process that can help you quickly identify a blown fuse. Here's how:

1. Safety First: Always turn off the ignition and any affected circuits before removing or testing fuses.
2. Locate the Fuse Box: Refer to the "Quick Answer" section or your owner's manual to find the correct fuse box.
3. Identify the Suspect Fuse: Look for the fuse corresponding to the non-working component using the provided diagrams or the fuse box lid legend.
4. Visual Inspection: Many fuses have a clear plastic body. Look for a broken wire or discoloration within the fuse. A blown fuse will show a visibly broken metal strip.
5. Use a Fuse Tester or Multimeter:
   • Fuse Tester: These inexpensive tools light up if a fuse is good. Simply touch the probes to the test points on top of the fuse (two small metal dots).
   • Multimeter: Set your multimeter to the "ohms" or "continuity" setting. Remove the fuse from its slot and touch the probes to each metal blade of the fuse. A good fuse will show very low resistance (close to zero ohms) or indicate continuity (the multimeter will beep). A blown fuse will show an open circuit or infinite resistance.
6. Replace if Blown: If the fuse is blown, replace it with a new fuse of the exact same amperage rating and type. Never use a fuse with a higher amperage rating, as this can lead to serious electrical damage or fire.

Common Blown Fuses on This Vehicle

While any fuse can blow, certain circuits on a Peterbilt 389 might experience more frequent issues due to wear, common accessory usage, or specific system demands. If you have a component failure, always check the relevant fuse first.

• Cigar Lighter/12V Power Outlets (Fuses C2, F14, S2): These fuses are often overloaded by high-draw accessories (inverters, portable refrigerators, phone chargers) or if a foreign object is inserted into the outlet. If an outlet stops working, check these fuses first.
• Blower Motor Fuses (F10, C13, S1): The blower motor can draw significant current, especially on higher settings or if the motor starts to seize up. If your HVAC fan isn't working, check the corresponding blower motor fuse for the cab and/or sleeper.
• Headlight Fuses (F4, F5, F6, F7): While not extremely common, a short in the headlight circuit or a failing bulb can sometimes cause these fuses to blow, resulting in a loss of low or high beams on one or both sides.
• Trailer Brake Controller Fuse (F9): If your trailer brakes are not functioning correctly, or you have no power to your trailer brake controller, this fuse is a prime suspect. Issues with trailer wiring are often the cause of this fuse blowing.
• Radio/Infotainment Fuse (C1): If your radio or entertainment system suddenly goes dead, this fuse is the first thing to check. Issues can arise from internal shorts, faulty wiring, or even aftermarket accessory installation.

When a fuse blows, it's a symptom of an underlying issue, not just the problem itself. While replacing the fuse might restore functionality, if it blows again, it indicates a deeper electrical problem (e.g., a short circuit, overloaded component, or failing motor) that needs professional diagnosis.

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