Which wires give constant, ignition and ground on a 2018 Chevrolet Low Cab Forward 6500XD?
On a 2018 Chevrolet Low Cab Forward 6500XD, take constant power from the Black/Yellow wire at the ignition switch plug B-130, steering column, pin 3, ignition from the White/Red wire at the ignition switch plug B-130, steering column, pin 6, and ground to the Black wire at the OBD port (data link connector B-31), pin 4. Meter every wire first.
Meter every wire before you tap it. Colors change with trim and build date.
OBD-II port:Near the steering columnBest power spot:Ignition switch plug B-130System voltage:12VEngine:Diesel
Where do I get constant, ignition and ground on a 2018 Chevrolet Low Cab Forward 6500XD?
GM prints every pin of the ignition switch plug, so constant, ignition and accessory can all come from one spot on the steering column.
Option 1 All four wires
Ignition switch plug B-130
On the steering column, behind the shroud.
Constant
Black/Yellow
Ignition switch plug B-130, steering column, pin 3Battery feed from fusible link FL-12. Pin 4 (Black/Red) is a second battery feed from FL-6.
Each chip shows the main insulation color with its stripe. Source: GM's 2018 6500XD electrical body builders manual.
Where are the brake, door, speed and CAN wires on a 2018 Chevrolet Low Cab Forward 6500XD for advanced 360 multicam and video telematics installs?
Circuit
Wire color
Location and what it does
Rear marker relayPositive +Not yet checked
Light Green/Black
Rear manufacture connector J-118, end of frame, pin ASwitched output from the marker lamp relay, for body lamps.
Rear battery feedPositive +Not yet checked
Red
Rear manufacture connector J-118, end of frame, pin BBattery voltage from fuse F36. Pin D (Black/Blue) is ground.
Rear dome relayPositive +Not yet checked
White/Black
Rear manufacture connector J-118, end of frame, pin CSwitched output from the rear dome lamp relay.
Power outletPositive +Not yet checked
Red/Yellow
Power outlet B-33, pin 1Ignition voltage from fuse A-1.
DoorsNot foundNot yet checked
Not found
Not foundNot read from GM's tables.
Vehicle speedNot foundNot yet checked
Not found
Not foundSpeed travels on the CAN bus on this truck.
CAN busDataNot yet checked
Green/White (high)
Green (low)
OBD port (data link connector B-31), pins 6 and 14ISO 15765 CAN 2. Never cut or splice these wires.
Source: GM's 2018 6500XD electrical body builders manual (OEM connector end views and fuse table). Headlight, door and speed wires were not read.
Where are the fuse boxes and ground points on a 2018 Chevrolet Low Cab Forward 6500XD?
Cab fuse and relay centerIgnition fusesF-18 "IGNITION1" (10A), F-20 ECM, F-21 meter, F-24 audio and accessory (15A), F-3 room lamp, audio and OBD port (10A).
StarterF-13Starter circuit. Never tap it.
Ground pointsOBD port groundsPins 4 and 5 of the OBD port, or clean bare cab metal. Never the battery negative post.
From GM's 2018 6500XD electrical body builders manual. Our team has not yet checked these on a truck.
Where is the OBD-II port on a 2018 Chevrolet Low Cab Forward 6500XD?
OBD II
Diagnostic portOBD-II port: near the steering columnPlug-in GPS trackers and OBD harnesses connect here. Check the port before you plan the install.
Which years share wiring with the 2018 Chevrolet Low Cab Forward 6500XD?
This page2018Chevrolet LCF 6500XD.
Same truckIsuzu FTRSame chassis, colors not confirmed from an Isuzu document.
Not this page2019 and newerGM publishes a different manual for later years. We have not read it yet.
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This page covers the 2018 Chevrolet Low Cab Forward 6500XD medium duty truck, the Class 6 cab-over built with Isuzu.
Every color here comes from GM's own 2018 6500XD body builders manual, which prints each connector pin as text. Our own team has not yet metered these on a 2018 truck, and each row says so.
Written by API Signal, fleet GPS and camera installers for 35+ years across Georgia, South Carolina and North Carolina, installing every major telematics and camera brand. Every wire on this page lists its source.
Test every wire with a meter before you tap it
No wiring information is ever guaranteed. Colors and locations change with trim, options and build date, and the manufacturer can change them in the middle of a model year. We share this as a starting point for installers, and you are responsible for confirming every connection on the truck in front of you.
Common questions about 2018 Chevrolet Low Cab Forward 6500XD wiring
What wire is constant power on a 2018 Chevrolet Low Cab Forward 6500XD?
Black/Yellow at the ignition switch plug B-130, steering column, pin 3. Battery feed from fusible link FL-12. Meter it before you tap it.
What wire is ignition on a 2018 Chevrolet Low Cab Forward 6500XD?
White/Red at the ignition switch plug B-130, steering column, pin 6. IG1. Meter it before you tap it.
Where is the reverse wire on a 2018 Chevrolet Low Cab Forward 6500XD?
Red/Blue (positive +) at the rear combination lamps J-73 (left) and J-74 (right), backup lamp pin (J-73 pin 5, J-74 pin 5). Backup lamp supply from fuse A-4. Meter it before you tap it.
Where is the brake wire on a 2018 Chevrolet Low Cab Forward 6500XD?
Green (positive +) at the rear combination lamps J-73 (left) and J-74 (right), pin 2. Stop lamp relay output. Meter it before you tap it.
Where is the CAN bus on a 2018 Chevrolet Low Cab Forward 6500XD?
Green/White (high) and Green (low) at the OBD port (data link connector B-31), pins 6 and 14. ISO 15765 CAN 2.
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