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Before diving into the diagram, it is important to understand that the 2015 Peterbilt 389 utilizes a multiplexed electrical system (often referred to as the "Paccar MX" electrical architecture).
Where to Find and Read the 2015 Peterbilt 389 Fuse Panel Diagram (No More Electrical Guesswork)
| Fuse # | Amperage | Circuit / Component | Common Failure Symptom | | :--- | :--- | :--- | :--- | | | 10A | Trailer Tail Lamps | Trailer running lights out | | 2 | 15A | Cigarette Lighter / Power Port | No power to phone charger | | 3 | 5A | Radio Memory (Constant) | Radio resets every time you start truck | | 4 | 10A | HVAC Blower Motor (High speed) | AC only works on low/medium | | 5 | 20A | Windshield Wipers | Wipers stopped mid-cycle | | 6 | 10A | Right Turn Signal / Hazard | No right blink on dash or trailer | | 7 | 10A | Left Turn Signal / Hazard | No left blink | | 8 | 5A | Instrument Cluster (Ignition) | Gauges dead, check engine light dim | | 9 | 15A | Do not use (Body Builder spare) | N/A | | 10 | 10A | Stop Lamps (Brake lights) | No brake lights (check relay too) | | 11 | 25A | Cab Power Windows | Windows won't roll up/down | | 12 | 10A | Back-up Alarm / Reverse Lights | No reverse lights or "beep" | | 13 | 15A | ECM Ignition Feed | Truck cranks but won't start | | 14 | 5A | VECU (Vehicle ECU) Sleep power | Battery drain overnight | | 15 | 30A | HVAC Blower Motor (Main) | No air from vents at all | | 16 | 10A | Marker Lights (Clearance) | No cab roof or fender lights | | 17 | 15A | Horn | Horn weak or dead | | 18 | 10A | Dome / Courtesy Lights | No interior cab lights | | 19 | 5A | Smart Wheel (Steering wheel controls) | Radio or cruise buttons not working | | 20 | 30A | Power Seat (If equipped) | Seat won't move | | 21 | 15A | Trailer ABS Power | Trailer ABS light on dash | | 22 | 10A | Heated Mirrors | Mirrors not defrosting | | 23 | 20A | Fuel Heater / Water separator | Gelling fuel in cold weather | | 24 | 10A | Cruise Control | Cruise won't set | | 25 | 5A | Bendix ABS Cab Module | No wheel speed on dash; ABS light on | | 26 | 15A | Trailer Turn Signal (Left) | Trailer left blink fast or absent | | 27 | 15A | Trailer Turn Signal (Right) | Trailer right blink fast or absent | | 28 | 10A | Park Brake / Dump Valve | Air suspension won't dump | | 29 | 5A | Telematics / ELD | No GPS or e-log connection | | 30 | 30A | Windshield Washer Pump | Washer fluid won't spray | 2015 Peterbilt 389 Fuse Panel Diagram
| Fuse Slot | Amperage | Component | | :--- | :--- | :--- | | | 40A Maxi | Blower Motor (HVAC) | | PDC 2 | 30A Maxi | Windshield Wipers | | PDC 3 | 50A Maxi | Engine Fan Clutch | | PDC 4 | 60A Maxi | Alternator charge output (to battery) | | PDC 5 | 30A Maxi | ABS Module power | | PDC 6 | 10A Mini | ECM Main Power (Keep alive) | | PDC 7 | 15A Mini | Starter Solenoid (signal) | | PDC 8 (MX-13) | 20A Mini | DEF (Diesel Exhaust Fluid) Heater | | PDC 8 (ISX) | 15A Mini | Injector Driver Module |
Save this post for roadside troubleshooting. 🚛 Before diving into the diagram, it is important
The 2015 model year uses blade-type fuses (mini and ATO). Always replace with the same amperage.
2015 Peterbilt 389 utilizes a multi-panel fuse system designed to support its complex modern electronics. While the diagrams are essential for troubleshooting, their utility is often impacted by scattered physical locations and occasionally ambiguous labeling. Fuse Panel Locations Always replace with the same amperage
🔧 Tip: Always use a test light—don’t guess and pull fuses blind.
This box is critical for engine-starting circuits. If the cab fuses are fine but the truck won’t start, look here.
📍 Driver side, under dash panel (left of steering column).
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