Key-start trucks. The last full year before the 2022 refresh.
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Which wires give constant, ignition and ground on a 2021 Chevrolet Silverado 1500?
On a 2021 Chevrolet Silverado 1500, take constant power from the Red/Violet wire at the BCM blue 27-pin plug (X2), pin 4 and ignition from the Violet/Black wire at the BCM green 25-pin plug (X3), pin 6, and ground to clean, bare body metal. Meter every wire first.
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.
This page covers the key-start 2021 Chevrolet Silverado 1500, the last full model year before Chevrolet refreshed the truck for 2022. GM did not publish a separate 2021 electrical manual. Its upfitter site lists the 2020 Silverado 1500 manual for 2021 trucks, and that is the source for this page.
That means the colors and pins below are GM's 2020 data applied to 2021, not a separate 2021 document. An aftermarket install guide also treats 2019 to 2022 LTD key-start trucks as one install. Our own team has not yet metered these on a 2021 truck, and each row says so.
OBD-II portDriver side lower dash
Best power spotBCM, driver side dash
System voltage12V
Ignition typeKey start
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Where do I get constant, ignition and ground on a 2021 Chevrolet Silverado 1500?
Take constant, ignition and ground from the same spot. Each box below is a complete set, so you never have to run one wire to the dash and another to the engine bay.
Option 1
At the ECM
Engine computer. Engine bay, left front, behind the driver side headlight.
Constant
Red/Brown
ECM plug X1 (49-pin, black), pin 34Always hot. Own 15A fuse (F78) in the underhood fuse block.
Ignition
Violet/Green
ECM plug X1 (49-pin, black), pin 47Hot in run and start. Own 15A fuse (F46).
Ground
Black/White
ECM plug X2 or X3, pin 73Runs to ground point G114, engine compartment, left side on the body.
Gas V8 and 4.3 V6 trucks. The 2.7 turbo and 3.0 diesel use other pins (listed under Before you tap). Thin wires in sealed plugs, so reseal every tap.
Option 2 Easiest
At the BCM
Body computer. Behind the driver side of the dash, outboard of the steering column.
Constant
Red/Violet
BCM blue 27-pin plug (X2), pin 4Always hot, 30A fuse. The biggest constant of the three spots.
Ignition
Violet/Black
BCM green 25-pin plug (X3), pin 6Hot in run and start. Use it as an ignition sense wire.
Ground
Black
BCM white 26-pin plug (X1), pin 1Runs to ground point G200, behind the driver kick panel.
All three wires inside the cab, a few inches apart, and the constant has the biggest fuse.
Option 3
At the ignition switch
Right side of the steering column, behind the wheel.
Constant
Red/Blue
Ignition switch, black 6-pin plug, pin 4Always hot, but only a 2A fuse. Do not power a device from it.
Ignition
Violet/Black
Ignition switch, black 6-pin plug, pin 5Hot in run and start
Accessory
Violet/Yellow
Ignition switch, black 6-pin plug, pin 3Hot in accessory and run
Ground
Body ground
No ground at the switchUse ground point G200 behind the driver kick panel, or clean bare metal.
These are small signal wires. Good for an ignition sense wire. Take device power from the BCM or ECM instead.
Power pins from GM's 2020 Silverado 1500 body builder manual, which GM lists for 2021 trucks. Every pin, color and fuse above is the same across the GM manuals we checked for 2019, 2020 and 2022 LTD trucks.
What are the turn signal, reverse and light wires on a 2021 Chevrolet Silverado 1500?
Circuit
Wire color
Location and what it does
Left turnPositive +Not yet checked
Blue/White (front)
Yellow/Blue (rear)
BCM under driver side dash, brown 26-pin plug, pin 2 front, pin 1 rearFlashes with the left signal
Right turnPositive +Not yet checked
Green/Violet (front)
Brown/Green (rear)
BCM under driver side dash, black 26-pin plug, pin 3 front, pin 4 rearFlashes with the right signal
Park lightPositive +Not yet checked
Violet/Gray (left)
Gray/Brown (right)
Underhood fuse box, 44-pin plug X2, pin H3 left, pin H5 rightOn with the park lights
HeadlightNegative -Not yet checked
White/Violet
BCM under driver side dash, white 26-pin plug, pin 16Headlight switch input, not lamp power
ReversePositive +Not yet checked
Green/White
Passenger kick panel, black 76-pin plug, pin 40Hot in reverse
Dome lightPositive +Not yet checked
Gray
BCM under driver side dash, white 26-pin plug, pin 23On with the dome light
Each chip shows the main insulation color with its stripe. Source: GM's 2020 Silverado 1500 manual, which GM lists for the 2021 truck. Not separately confirmed on a 2021 truck.
Where are the brake, door, speed and CAN wires on a 2021 Chevrolet Silverado 1500?
Circuit
Wire color
Location and what it does
BrakePositive +Not yet checked
Violet/White
BCM under driver side dash, black 26-pin plug, pin 11Hot with the brake pedal pressed. Sense only, no load.
Driver doorNegative -Not yet checked
Gray or
Pink (power windows)
Gray (manual windows)
Power windows: driver door latch, green 10-pin plug, pin 1. Manual windows: BCM gray 26-pin plug, pin 25Door switch. Where you tap it depends on the window type.
StarterPositive +Not yet checked
Yellow
Underhood fuse box, gray 44-pin plug X3, pin B1Hot only while cranking
Vehicle speedAC signalNot yet checked
Green/Gray
Passenger kick panel, black 76-pin plug, pin 12Speed signal. AC pulse, so use a device input made for it.
TachAC signalNot yet checked
Yellow/Violet
Camshaft position sensor, front of the engine, 3-pin plug, pin 3Engine speed. Applies to the V8s and 4.3 V6. The 3.0 diesel uses Violet/Black on a different sensor. The 2.7 turbo was not checked.
HoodNegative -Not yet checked
Brown/Green
BCM under driver side dash, black 26-pin plug, pin 24Hood open input
CAN busDataNot yet checked
Blue (high)
White (low)
BCM under driver side dash, white 26-pin plug, pin 25 high, pin 24 lowFor CAN-clip installs. Never cut or splice it.
Source: GM's 2020 Silverado 1500 manual, listed by GM for 2021.
Which years share wiring with the 2021 Chevrolet Silverado 1500?
This page2021GM lists its 2020 Silverado 1500 manual for 2021 trucks. No separate 2021 manual exists.
Same wiring2019 and 2020Same pins and colors in GM's manuals. The 2022 LTD matches on everything except the tach wire.
Not this page2022 refreshPush-button start only, with a new electrical system.
Where are the fuse boxes and ground points on a 2021 Chevrolet Silverado 1500?
InteriorLeft and right instrument panel fuse blocksOne on each end of the dash, behind the end covers.
Under the hoodEngine compartment fuse blockDriver side, near the battery. The ECM fuses are F78 (constant, 15A) and F46 (ignition, 15A).
Ground pointsG200 and G114G200 is behind the driver kick panel, below the A-pillar. G114 is in the engine bay, left side, on the body.
Ground point and ECM fuse locations come from GM's body builder manuals. Fuse block locations come from published fuse diagrams for 2019 to 2022 Silverado trucks. Our team has not yet checked them on a truck.
Where is the OBD-II port on a 2021 Chevrolet Silverado 1500?
OBD II
Diagnostic portOBD-II port: driver side lower dashPlug-in GPS trackers and OBD harnesses connect here. Check the port before you plan the install.
Common questions about 2021 Chevrolet Silverado 1500 wiring
What wire is constant power on a 2021 Chevrolet Silverado 1500?
Red/Violet at the BCM blue 27-pin plug (X2), pin 4. Always hot, 30A fuse. Meter it before you tap it.
What wire is ignition on a 2021 Chevrolet Silverado 1500?
Violet/Black at the BCM green 25-pin plug (X3), pin 6. Hot in run and start. Meter it before you tap it.
Where is the reverse wire on a 2021 Chevrolet Silverado 1500?
Green/White (positive +) at the passenger kick panel, black 76-pin plug, pin 40. Hot in reverse. Meter it before you tap it.
Where is the brake wire on a 2021 Chevrolet Silverado 1500?
Violet/White (positive +) at the BCM under driver side dash, black 26-pin plug, pin 11. Hot with the brake pedal pressed. Meter it before you tap it.
Where is the vehicle speed signal on a 2021 Chevrolet Silverado 1500?
Green/Gray at the passenger kick panel, black 76-pin plug, pin 12. Speed signal. Meter it before you tap it.
Where is the CAN bus on a 2021 Chevrolet Silverado 1500?
Blue (high) and White (low) at the BCM under driver side dash, white 26-pin plug, pin 25 high, pin 24 low. For CAN-clip installs.
Which years share wiring with the 2021 Chevrolet Silverado 1500?
2019 and 2020. Same pins and colors in GM's manuals.
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