Understanding the wiring for an LS swap OBD2 system is crucial for a successful engine conversion. This guide provides a detailed walkthrough of building a custom fuse block and wiring an OBD2 diagnostic port for your LS swap project. This setup is applicable to various LS engine swaps, including LT1, LS1, and Vortec truck engines.
Essential Components for Your LS Swap OBD2 Wiring
Before diving into the wiring process, gather the necessary parts for the fuse block and OBD2 diagnostic port.
OBD2 Diagnostic Port:
- OBD2 Port Connector (16 Pin): Source from electronic component suppliers like Mouser (Part# 829-12110250).
- OBD2 Port Terminals: These connect the wires to the OBD2 port (Mouser Part# 829-12129373).
- Terminal Lock: Secures the terminals in place (Mouser Part# 829-12160437).
- Check Engine Light (MIL): A standard indicator lamp.
Fuse Block and Relays:
- Fuse Block Housing Kit: This kit typically includes necessary terminals. Dorman Part# 85668 is a readily available option from retailers like AutoZone or RockAuto.
- Relay Sockets: Choose sockets that can be mounted on the fuse block (e.g., SRLY-2 from AllElectronics).
- Relays (30 Amp): Select relays appropriate for the current draw of your circuits (e.g., RLY-351 from AllElectronics).
- Relay Terminals (14-18 AWG): Ensure these terminals are compatible with the relay sockets and wiring gauge (Mouser Part# 571-42238-2).
Constructing the Fuse Block
The relay sockets often come with pre-installed wires. Replace these with heavier gauge wires (14-18 AWG) using crimp connectors and solder for a robust connection.
Connect a heavy-gauge wire to the relay’s output leg and three bussed fuse terminals to the fuse block. Secure these terminals in their designated slots.
Connect a red wire to the relay’s input leg. This wire will be connected to a constant 12V+ battery source, providing power to the relay and a dedicated fuse.
A 16 AWG gray wire connects to the fuel pump relay’s output. A pink wire connects to the other relay’s coil, providing switched power activated by the ignition key.
Wiring the Remaining Fuse Block Terminals
Group the remaining pink wires and connect them to three fuses. These will be powered when the ignition key is turned on. Include a wire for the check engine light (MIL).
Connect an orange wire to provide constant battery power to the PCM. Jumper this to the fuel pump relay’s input terminal. Finally, ground each relay coil using a jumper wire. The PCM will control the fuel pump relay via a dedicated control wire.
Wiring the OBD2 Diagnostic Port
Prepare wires (approximately 6 feet long) for the diagnostic port and check engine light, ensuring they can reach the vehicle’s interior.
Standard OBD2 Wiring (LS1, Vortec):
- Pin 2: Serial Data (from PCM)
- Pin 4 & 5: Ground (Pin 5 is often sufficient, but some tools require both)
- Pin 16: Battery Positive (12V+)
LT1 Specific Wiring:
- 1996-97 LT1: Pin 6 (Diagnostic Request), Pin 9 (UART Serial Data)
- 1995 LT1: Pin 9 (Serial Data – Note: 1995 LT1s used an OBD2 port but were not fully OBD2 compliant)
This comprehensive guide provides a solid foundation for wiring your LS swap OBD2 system. Remember to consult your specific vehicle and PCM documentation for any variations in wiring requirements. Always double-check all connections before powering on the system.
