Integrating an OBD2 port into your LS swap project is crucial for diagnostics and tuning. This guide provides a detailed walkthrough on building a custom fuse block and wiring an OBD2 diagnostic port, essential for any LS swap to ensure proper functionality and easy troubleshooting. Whether you’re working on an LT1, LS1, or Vortec truck engine, the fundamental principles remain consistent.
Essential Components for Fuse Block and OBD2 Port
Before commencing the wiring process, gather all necessary components. Below is a comprehensive parts list to construct your fuse block and OBD2 diagnostic port setup.
OBD2 Diagnostic Port Parts
| Part Description | Vendor | Part Number | Quantity Needed |
|---|---|---|---|
| OBD2 Port Plastic Connector, 16 Pin | Mouser | 829-12110250 | 1 |
| Terminals – for OBD2 port | Mouser | 829-12129373 | 4 |
| Terminal Lock – secures terminals | Mouser | 829-12160437 | 2 |
| Lamp (for check engine light) | AllElectronics | Check inventory | 1 |
Fuse Block & Relays
| Part Description | Vendor | Part Number | Quantity Needed |
|---|---|---|---|
| Fuse Block Housing kit (terminals incl.) | RockAuto / Terminal Supply Co. | 85668 | 1 |
| Relay Socket | AllElectronics | SRLY-2 | 2 |
| Relay 30 Amp | AllElectronics | RLY-351 | 2 |
| Relay Terminal 14-18 AWG | Mouser | 571-42238-2 | 8 |
Note: Automotive parts stores like AUTOZONE may also carry the Dorman fuse block (part # 85668) at competitive prices.
Fuse Block Wiring: Step-by-Step Guide
Let’s delve into the fuse block wiring process. While relay sockets from vendors like AllElectronics often come with pre-installed wires, it’s recommended to replace these with higher gauge wires suitable for automotive applications. Ensure you have extra terminals on hand for potential rework or additional connections for both the OBD2 port and fuse block. Always crimp and solder your connections for robust and reliable performance.
Here’s a breakdown of the fuse block wiring steps:
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Prepare the Fuse Block Terminals: Begin by modifying the fuse block terminals. Separate a set of four bussed terminals into a group of three and a single terminal. This configuration allows for both grouped and individual fused circuits.
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Install Output Terminals: Crimp and solder heavy gauge wires to the designated output terminals. These terminals will distribute power to your circuits.
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Mount Relay and Fuse Terminals: Insert the prepared terminals into the relay output leg and the bussed fuse terminals into the fuse block housing. Ensure they are firmly seated until they click into place.
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Connect Relay Input Terminal: Install the relay input terminal. This terminal, typically connected to a red wire, will be your 12V+ battery power source. It provides constant power to the fuse block and fuel pump relay.
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Wire Relay Outputs and Keyed Power: Connect the gray 16 AWG wire to the output leg of the fuel pump relay. For the second relay, connect a pink wire terminal to the relay coil location. This pink wire will serve as the KEY HOT power source, activating the relay and subsequently powering the bussed fuses when the ignition is on.
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Group Keyed Hot Fuses: Utilize the remaining fuse and relay terminals to group your PINK wires for the key-hot fuses. This organizes your circuits based on ignition-switched power.
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Constant Power and Fuel Pump Relay Input: Add the ORANGE constant battery power wire for the PCM (Powertrain Control Module) and create a jumper wire to connect to the fuel pump relay input terminal. This ensures continuous power to critical components and the fuel pump relay.
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Ground and Fuel Pump Relay Control: Finally, install the ground wires for each relay coil, using a jumper from the first relay to the second for efficient grounding. Connect the fuel pump relay control wire from the PCM to the designated relay coil terminal. The PCM will supply 12V+ to trigger the fuel pump relay when needed.
The coiled pink, orange, and black wires are intended for the OBD2 diagnostic port and the check engine light, designed to be long enough to reach inside the vehicle cabin for convenient access.
OBD2 Diagnostic Port Wiring Diagram and Pinout
Wiring the OBD2 port correctly is essential for accessing vehicle diagnostics. Here’s the standard OBD2 port pinout for LS swaps and Vortec truck engines:
- Pin 2: Serial Data – Connects to the PCM for data communication.
- Pins 4 & 5: Ground – Pin 5 is typically sufficient for ground, but some scan tools may require ground on Pin 4 as well. Connect both for maximum compatibility.
- Pin 16: 12V+ Battery – Connect to a constant 12V+ battery source to power the OBD2 port.
Note for LT1 (96-97) Specific Wiring: LT1 OBD2 systems (96-97 models ONLY) have additional wiring requirements:
- Pin 6: Diagnostic Request/Field Output Enable
- Pin 9: UART Serial Data
1995 LT1 models used an OBD2 port connector but were not fully OBD2 compliant. They used Pin 9 for serial data instead of Pin 2 and lacked serial data on Pin 2.
(Note: Since there was no explicit OBD2 wiring diagram image in the original article, a placeholder pictures/obd2_port_wiring_diagram_placeholder.jpg is used. In a real scenario, a wiring diagram image would be created and inserted here, with alt text describing the pinout and connections.)
By following these steps, you can confidently build a robust fuse block and wire your OBD2 port for your LS swap project, ensuring diagnostic accessibility and electrical system reliability. Remember to double-check all connections and consult your specific engine and PCM documentation for any variations.
