Mastering Diamond Logic Electrical System | How to Program Aux Switches and Telematics for Custom Upfits
There’s a distinct satisfaction when you flip a switch in the cab and your custom equipment responds instantly—knowing you programmed that connection yourself, without cutting a single wire.
TL;DR
The Diamond Logic® electrical system is International’s smart, factory-integrated platform that simplifies custom upfitting. Using Diamond Logic Builder (DLB) software, you can program auxiliary switches, set interlocks, and control body equipment directly through the truck’s Body Controller (BCU). The system uses pre-engineered features and advanced ladder logic to eliminate complex aftermarket wiring. Remote Power Modules (RPMs) centralize electrical connections, allowing “plug and play” installation. Programming requires DLB software (annual subscription around $648), a compatible diagnostic adapter like Nexiq USB-Link 3, and an understanding of switch mapping and pin conflicts.
Key Takeaways
- Diamond Logic Eliminates Messy Wiring: The factory-integrated system uses Remote Power Modules (RPMs) to centralize connections, replacing complex aftermarket harnesses .
- DLB Software is Essential: Diamond Logic Builder (DLB) is the diagnostic and programming tool for configuring aux switches, interlocks, and custom logic .
- Aux Switches Control Up to 20 Amps: Each RPM output is software-fused with programmable limits (default 20A) and can be interlocked with vehicle conditions like speed or gear .
- Advanced Logic Uses Ladder Logic: You can write custom control programs using ladder logic—a visual programming language that’s easier to learn than traditional code .
- Watch for Pin Conflicts: When adding custom logic, check that you’re not mapping outputs to pins already used by pre-engineered features .
- The Diamond Partner Program Helps: International offers free support to Truck Equipment Manufacturers (TEMs), streamlining the upfit process .
Understanding the Diamond Logic System: The Brain Behind the Switches
The Diamond Logic® electrical system is what makes International trucks so upfit-friendly. It’s a factory-installed, multiplexed architecture that links vehicle controls directly to body equipment . Think of it as the truck’s nervous system—centralized, intelligent, and designed to talk to add-on components without requiring a tangle of aftermarket wires.
How It Works
Instead of running individual wires from every cab switch to every piece of equipment, Diamond Logic uses a Body Controller (BCU) as the central brain. When you press a programmed aux switch, the BCU receives that signal and activates the corresponding output on a Remote Power Module (RPM) . The RPM then powers your equipment.
The key benefits are simple:
- Faster upfitting: Pre-engineered features and modular harnesses speed up installation .
- Lower lifecycle costs: Less wiring means fewer electrical gremlins down the road .
- Greater productivity: You can program automated tasks and interlocks that prevent errors .
But how do you actually program this system?
Diamond Logic Builder (DLB): Your Programming Toolkit
To program aux switches and customize logic, you need Diamond Logic Builder (DLB) software. It’s the official tool for configuring the body controller and diagnosing electrical systems on International trucks .
What DLB Does
- Reads and clears fault codes in the Body Controller (BCU)
- Customizes electrical logic for switches, lights, and relays
- Adds custom features or changes factory settings using templates
- Monitors live input/output data and troubleshoots electrical systems
- Programs new BCUs or restores configurations after replacement
Getting DLB: Options and Cost
DLB is available as an annual subscription, typically costing around $648 per year . You can purchase it directly from International’s tool store. Keep in mind that DLB is compatible with Windows 11, and you’ll need a supported data link adapter like the Nexiq USB-Link 3 to connect to the truck’s diagnostic port .
There’s also a Fleet Edition that focuses on diagnostics and DTC reading but does not allow parameter changes or programming, so make sure you get the full version for custom upfitting .
System Requirements
Before installing DLB, ensure your computer meets these specs :
- Windows 10 or 11 (64-bit)
- 2.0 GHz dual-core processor or faster
- 4 GB RAM (8 GB recommended)
- 10 GB free disk space
- Administrative rights for installation
What’s the first step when you fire up DLB?
Programming Aux Switches: Step-by-Step
Programming aux switches with DLB involves selecting pre-engineered features or building custom logic. Let’s break down both approaches.
Approach 1: Using Pre-Engineered Features (The Easy Way)
For common applications, International offers pre-engineered feature codes that handle the programming for you. For example, if your truck needs an interlocked switch that shuts off above 30 MPH for work lights, you can use Feature 60ACH .
Example: Feature 60ACH – Interlocked Aux Switches
This feature provides two 2-position latched rocker switches, each controlling a 20-Amp output. The outputs automatically disengage when vehicle speed exceeds 30 MPH . This is perfect for rear work or scene lights—if the driver forgets to turn them off before driving away, the system does it for them.
Programmable parameters for this feature include :
| Parameter | What It Does |
|---|---|
| TEM_Aux1_Speed_Interlock_Param | Sets the speed threshold (default 30 MPH) |
| TEM_Aux1_Gear_Interlock_Param | Sets transmission gear conditions (default Neutral) |
| TEM_Aux1_w_lock_Output_Fuse | Software fuse limit (default 20A, adjustable 0.1-20A) |
| TEM_Aux1_Interlock_Latches_Off | When enabled, output stays off until switch is recycled |
| TEM_Aux1_w_int_LoadShed_Level | Priority level for load shedding |
The feature also offers extensive interlocking options. The TEM_Aux1_Misc_Interlock_Param lets you choose from conditions like :
- 0: No interlocks
- 1: Activate when park brake is set
- 2: Activate when park brake is not set
- 3: Activate when a door is open
- 5: Activate when PTO is engaged
- 9: Activate when vehicle exceeds a set speed
- 10: Activate when vehicle is below a set speed
- 13/14: Activate based on transmission gear (park/neutral/reverse)
Approach 2: Advanced Logic Programming (For Custom Applications)
For unique requirements, DLB lets you create custom logic using ladder logic—a visual programming language that looks like electrical schematics .
A simple example: Controlling a 40-Amp Circuit
If your truck was ordered with the Auxiliary 40 Amp Circuit (feature code 08XBK), all wiring is already in place .
- Remove the pre-engineered feature: You need to uninstall the default feature (595265 or 595AJH) to avoid conflicts with your custom logic .
- Build your ladder logic: Drag and drop elements to create control rungs. For example, you might create a rung where a custom switch controls the 40-Amp load, with a park brake interlock .
Custom_Switch02_A_Up ---[ ]---+---[ ]---( Forty_Amp_Load )
|
Park_Brake- Map to the right pins: The output “Forty_Amp_Load” is found in the Chassis tab. The switch input is from the Switches tab .
- Program to the vehicle: Once your logic is complete, click “Program to Vehicle” and wait for confirmation .
A More Complex Example: Waste Collection Vehicle Logic
The DLB manual shows a practical example for a waste collection vehicle :
- Rung 1: Strobe switch turns on strobe lights.
- Rung 2: Strobe lights output also turns on a dash indicator lamp.
- Rung 3: Flood lights turn on if either the flood light switch is ON or the transmission is in REVERSE.
This shows how you can combine inputs (OR logic) and set up indicator lamps to confirm equipment is running.
What about software settings for specific auxiliary outputs?
Key Parameters for Aux Switch Programming
The Electrical Systems Integration Guide provides detailed parameters for six auxiliary outputs (Aux 1 through Aux 6) controlled by the Remote Power Module .
Fuse Level Parameters:
| Parameter | Description | Default |
|---|---|---|
| TEM_Aux1_Output_Fuse_Param | Sets current limit (Amps) for Aux 1 | 20A |
| TEM_Aux2_Output_Fuse_Param | Sets current limit (Amps) for Aux 2 | 20A |
| …through Aux 6 | … | 20A |
Load Shed Level Parameters:
| Parameter | Description |
|---|---|
| TEM_Aux1_LoadShed_level | Priority level for load shedding (0=disabled, 1=lowest priority/sheds first, 3=highest priority/sheds last) |
These allow you to prioritize which circuits remain active when the electrical system is under heavy load.
Telematics Integration and Diagnostic Support
OnCommand Connection Integration
The Diamond Logic system links directly to International’s telematics platform, OnCommand Connection. This allows remote monitoring of fault codes and vehicle health, with action plans for over 18,000 fault codes.
Diagnostics with DLB
DLB includes robust diagnostic features:
- Live I/O Monitoring: See real-time status of switches, relays, and circuits .
- Fault Code Management: Read and clear active/inactive faults for the BCU and subsystems .
- Snapshot and Data Recording: Capture and graph parameters for trend analysis .
Template Management
DLB allows you to save entire configurations as templates (XML files). This is invaluable for fleet standardization—you can clone a configuration from one truck and apply it to others without rewriting logic .
Avoiding Common Pitfalls
Pin Conflicts
This is the most common issue when programming custom logic. The Diamond Logic system contains pre-engineered features that may already use certain input/output pins. When you create advanced logic, you must ensure you’re not mapping signals to pins already in use .
How to avoid conflicts:
- Print out the connector view and note which pins are used by pre-engineered features .
- Print the center panel view and note which switch positions are occupied .
- Use the DLB conflict warnings—the software will attempt to alert you when a pin conflict exists .
- Remap outputs if necessary—DLB can help you reassign conflicting features to different pins .
When Conflicts Happen
If two logic blocks are mapped to the same output, the last one enabled will lose its mapping. The output will be remapped as an internal variable—meaning it won’t connect to any physical output pin . Always check the Message tab for errors and verify your outputs are correctly assigned.
Know Your Switch Types
Diamond Logic uses two main switch types :
| Switch Type | Behavior | Best For |
|---|---|---|
| Two-Position Latched | Stays ON when pressed, OFF when pressed again. Remembers state after power loss. | PTO controls, most applications |
| Three-Position Momentary | Spring-returns to center. Up and Down are momentary. | Applications needing separate ON and OFF commands |
For the majority of switching needs, the two-position latched switch is recommended .
Defaults and Initial State
Some features have an Init_State parameter that determines if the output defaults to ON or OFF at key-on. When the box is checked, the output will be ON at ignition key-on; unchecked means OFF .
The Diamond Partner Program: Support for Upfitters
International’s Diamond Partner Program is designed to help Truck Equipment Manufacturers (TEMs) streamline the upfitting process . Benefits include:
- Access to an application engineer for assistance throughout the process
- Specification review to determine the best specs at the right cost
- Factory hole punching for upfitting, saving hours of work at dealerships
- Joint customer events including ride-and-drive experiences
The program is offered free of charge to TEMs and has signed up dozens of partners since its introduction .
Frequently Asked Questions
What is Diamond Logic Builder (DLB) software?
DLB is International’s diagnostic and programming tool for the Diamond Logic electrical system. It allows users to read fault codes, program auxiliary switches, and create custom logic for body equipment integration .
How much does Diamond Logic Builder cost?
A one-year subscription to DLB costs approximately $648. Licenses are not renewable after expiration; you must purchase a new key annually .
What hardware do I need to connect to the truck?
You need a compatible RP1210 data link adapter, such as the Nexiq USB-Link 3, and a connection to the truck’s 9-pin or 16-pin diagnostic port .
What is a Remote Power Module (RPM)?
An RPM is a centralized electrical module that provides fused outputs for body equipment. It eliminates complex wiring by allowing “plug and play” connections .
Can I program aux switches without DLB?
No. DLB is the official tool for programming switches, setting interlocks, and configuring custom logic on International trucks with Diamond Logic .
What is Advanced Logic in DLB?
Advanced Logic allows users to write custom control programs using ladder logic. This gives you maximum flexibility to create interlocking conditions, alarms, and automated control sequences for body equipment .
What are the limits on auxiliary outputs?
Each RPM output is software-fused with a default limit of 20 Amps, adjustable from 0.1 to 20 Amps. The 40-Amp circuit is available as a separate option .
References
Explore Official International and Upfitter Resources:
- International Diamond Logic Builder Official Page
- International Vocational Trucks and Diamond Logic
- International Electrical Systems Integration Guide (PDF)
- Diesel Laptops DLB Install Guide
What custom upfit have you programmed with Diamond Logic? Share your questions and tips in the comments below.
