This guide provides a comprehensive walkthrough for constructing a custom fuse block and wiring an OBD2 diagnostic port, utilizing the 829-12110250 Obd2 connector. This setup is adaptable for various vehicle applications, including LT1, LS1, and Vortec trucks.
Parts List and Preparation
Before starting, gather the necessary components for both the fuse block and the OBD2 diagnostic port. The key component for the OBD2 port is the 829-12110250 connector housing.
OBD2 Diagnostic Port:
- Connector Housing: 829-12110250 (Mouser)
- Terminals: 829-12129373 (Mouser) – 4 pieces
- Terminal Locks: 829-12160437 (Mouser) – 2 pieces
- Check Engine Light: (All Electronics – check lamps/indicators, inventory changes)
Fuse Block and Relays:
- Fuse Block Housing Kit (with terminals): 85668 (Dorman – available at AutoZone or RockAuto)
- Relay Sockets: SRLY-2 (All Electronics) – 2 pieces
- 30 Amp Relays: RLY-351 (All Electronics) – 2 pieces
- Relay Terminals (14-18 AWG): 571-42238-2 (Mouser) – 8 pieces
The Dorman 85668 fuse block kit can often be found at AutoZone for around $5.00 or even less at RockAuto.
Important Note on Relay Sockets: The relay sockets from All Electronics come with pre-installed wires and terminals. Discard these. They are not suitable for the current demands of this setup. Remove them by gently bending the tab with a small screwdriver and insert new, higher quality terminals rated for the appropriate amperage. Always crimp and solder all connections for maximum reliability.
Fuse Block Assembly
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Relay Output: Crimp and solder a heavy-gauge wire terminal to the output leg of each relay. Connect this terminal to three bussed fuse terminals.
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Install Terminals: Securely seat the relay output terminal and the three bussed fuse terminals into the fuse block until they click into place.
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Relay Input (Battery Hot): Connect a red wire (12v+ battery hot) to the input leg of one relay. This will provide constant power to the fuse at the end of the block.
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Fuel Pump Relay Output: Attach a gray 16 AWG wire to the output leg of the fuel pump relay.
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Key Hot Relay Coil: Connect a pink wire to the coil terminal of the other relay. This will be activated by the ignition key, powering the three bussed fuses.
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Key Hot Fuses: Group and connect the remaining pink wires to the first three fuses. These will be powered when the key is in the “on” position. Include a wire for the check engine light (MIL).
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PCM Constant Power: Connect an orange wire to provide constant battery power to the PCM. Add a jumper to the fuel pump relay input terminal.
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Relay Ground and Fuel Pump Control: Ground each relay coil using a jumper wire between them. Connect the PCM’s fuel pump control wire to the fuel pump relay coil terminal. The PCM will provide the 12v+ signal to activate the fuel pump relay.
OBD2 Diagnostic Port Wiring
Standard OBD2 Wiring (LS1, Vortec Truck):
- Pin 2: Serial Data (from PCM)
- Pin 4 & 5: Ground (Pin 5 is often sufficient, but some tools require both)
- Pin 16: 12v+ Battery Power
OBD2 Wiring for 1996-97 LT1:
- Pin 6: Diagnostic Request/Field Output Enable
- Pin 9: UART Serial Data (1995 LT1 used Pin 9 for Serial Data, but were not fully OBD2 compliant)
