Check the underhood power center first and match each slot number with its assigned circuit using the lid legend. High-amperage links for systems like starter, ABS, and cooling fans are located in this area, while smaller cabin circuits are grouped inside near the driver side dash.
Open the interior panel and use the printed key to trace lighting, infotainment, HVAC, and accessory lines. Each position is marked with a number and rating, typically ranging from 5A to 30A. Replacing a burned element requires matching the exact amperage to avoid wiring damage or repeated failure.
For quick diagnostics, use a test light or multimeter to confirm power at both terminals of each slot. If voltage appears on only one side, the strip inside has failed. Relays controlling fuel pump, ignition, and blower motor can be swapped with identical units nearby to verify faults without special tools.
2019 GMC 2500 fuse box diagram with fuse locations and relay assignments
Locate the engine bay power distribution unit and use the cover legend to identify each slot by number and amperage before pulling any component. Large cartridge links typically handle starter motor, alternator feed, and cooling fans, while standard blade inserts protect smaller circuits.
Match each position to its circuit using the printed key or service manual mapping. Headlamp control, trailer brake output, and horn circuits are grouped toward the front section, while ABS and transmission control modules are placed closer to the firewall side for shorter wiring paths.
Inside the cabin, remove the side panel near the driver footwell to access the interior block. This section contains low to mid-range rated inserts, usually between 5A and 30A, supporting radio, climate control, power outlets, and interior lighting systems.
Relay assignments are positioned in both compartments and are labeled with abbreviations such as IGN, F/PMP, or HVAC. These switching units manage high-load devices by controlling current flow without routing full power through dashboard switches.
Swap identical relays from non-critical systems, such as rear defrost or auxiliary ports, to test suspected failures. A working component placed in the same slot can confirm whether the issue lies in the switching unit or the controlled circuit.
Use a multimeter to verify voltage on both terminals of each slot while the system is active. Power on one side only indicates a blown internal strip, while no voltage suggests upstream wiring or battery feed problems.
Keep spare inserts of common ratings like 10A, 15A, and 20A in the vehicle. Always replace with the same rating to prevent overheating or damage to wiring harnesses and connected modules.
Underhood fuse box diagram with labeled circuits and amperage details
Open the engine compartment power center and read the cover chart to match each numbered slot with its circuit before removing anything. This mapping shows exact amperage values and prevents installing the wrong rated insert.
Main high-current links are positioned near the battery feed and typically range from 40A to 175A. These protect systems such as the starter motor, alternator output, electric cooling fans, and power steering assist where equipped.
Mid-range slots, often rated between 20A and 40A, supply components like trailer wiring circuits, fuel pump control, and anti-lock braking modules. These are grouped toward the center of the panel for balanced distribution.
Circuit labeling and layout interpretation
Each cavity is marked with abbreviations such as ECM, TCM, HVAC, or HDLP. ECM refers to engine control, while HDLP points to headlamp circuits. Reading these labels correctly allows quick tracing of faults without dismantling wiring harnesses.
Numbers printed beside each slot correspond to a legend either on the lid or in the service manual. Cross-check both sources if markings are worn or unclear to avoid confusion between similar positions.
Amperage selection and replacement guidance
Always replace a blown insert with the same rating, such as 10A, 15A, or 30A. Installing a higher value can lead to wire overheating, while a lower one may fail repeatedly under normal load conditions.
Use a test light across both terminals of each slot while the circuit is active. Power on only one side confirms an internal break, while no signal points to upstream supply issues like a faulty relay or damaged wiring.