Medium duty conventional truck. Key start. 9-pin diagnostic port.
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Which wires give constant, ignition and ground on a 2014 Peterbilt 325, 330, 337 and 348?
On a 2014 Peterbilt 325, 330, 337 and 348, take ignition from the Orange wire at the remote PTO connector, 12-pin, on the engine harness (optional), pin 7, wire label ORN1229, and ground to the White wire at the remote PTO connector, 12-pin, on the engine harness (optional), pin 8, wire label WHT1513. 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 2014 Peterbilt 325, 330, 337 and 348 with the multiplexed dash.
This page is short. Peterbilt prints one ignition wire and one ground for these trucks, both at the optional remote PTO connector, and the lamp wire colors for trailer and body wiring. No constant wire was found, so constant power is by fuse tap. Our own team has not yet metered these on a 2014 truck.
9-pin diagnostic portBelow the dash, left of the steering wheel
Best power spotCab fuse box, left side foot well
System voltage12V
Ignition typeKey
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Where do I get constant, ignition and ground on a 2014 Peterbilt 325, 330, 337 and 348?
Peterbilt prints an ignition wire and a ground at the remote PTO connector. No constant wire was found, so constant power is by fuse tap.
Option 1 Ignition and ground
Remote PTO connector
A 12-pin Deutsch plug on the engine harness, on trucks ordered with it.
Constant
Not found
Not foundNo constant wire was found in the manual. Peterbilt labels protected battery wires with a tag that starts with RED. Use option 2.
Ignition
Orange
Remote PTO connector, 12-pin, on the engine harness (optional), pin 7, wire label ORN1229Ignition power for remote PTO controls. Thin 18 gauge wire, so use it as a signal or for a small tracker only.
Ground
White
Remote PTO connector, 12-pin, on the engine harness (optional), pin 8, wire label WHT1513Engine ground.
From Peterbilt. This connector is an option for PACCAR PX-7 and PX-9 engines, so a truck may not have it. Peterbilt says the harnesses that feed the engine, the emissions parts and the data links may not be spliced, so connect at the plug.
Option 2 Constant and ground
Cab fuse box
In the left side foot well.
Constant
Fuse tap
Fuse box behind a corner cover in the left side foot wellThe fuse panel label could not be read, so no fuse position is given. Meter the slots with the key off, then on, and use an add-a-fuse tap. Peterbilt says never to add a fuse over 30 amps.
Ground
Ground stud
Ground stud on the lower outboard driver side of the firewall, at the cover platePeterbilt says to tie body grounds to this stud. The manual prints it with the 270 amp alternator hookup.
Locations from Peterbilt. The 2017 operator manual describes the same fuse panel as behind the driver side kick panel, below the ignition switch.
From Peterbilt's medium duty body builder manual (July 2017). Every Peterbilt wire carries a label that starts with its color code: RED is protected battery power, ORG or ORN is ignition, accessory or start power, and WHT is ground.
What are the turn signal, reverse and light wires on a 2014 Peterbilt 325, 330, 337 and 348?
Circuit
Wire color
Location and what it does
Left turnPositive +Not yet checked
Yellow
Peterbilt trailer and body builder lamp wiringLeft turn lamps. Peterbilt prints this color for its trailer and body wiring. The optional junction box behind the cab or at the end of the frame has the same circuit on a terminal strip.
Right turnPositive +Not yet checked
Light Green
Peterbilt trailer and body builder lamp wiringRight turn lamps. Peterbilt prints this color for its trailer and body wiring. The optional junction box behind the cab or at the end of the frame has the same circuit on a terminal strip.
Park lightPositive +Not yet checked
Brown (tail)
Black (clearance and marker)
Peterbilt trailer and body builder lamp wiringTail lamps are brown. Clearance and marker lamps are black, so do not mistake that wire for a ground.
HeadlightNot foundNot yet checked
Not found
Not foundWe found no source for this wire.
ReverseNot foundNot yet checked
Not found
Not foundWe found no source for this wire.
Dome lightNot foundNot yet checked
Not found
Not foundWe found no source for this wire.
Each chip shows the main insulation color with its stripe. Source: Peterbilt's medium duty body builder manual (July 2017) (trailer and body builder wire color table).
Where are the brake, door, speed and CAN wires on a 2014 Peterbilt 325, 330, 337 and 348?
Circuit
Wire color
Location and what it does
BrakePositive +Not yet checked
Red
Peterbilt trailer and body builder lamp wiringStop lamps. In this wiring the ground is White.
DoorsNot foundNot yet checked
Not found
Not foundWe found no source for this wire.
Parking brakeNot foundNot yet checked
Not found
Not foundWe found no source for this wire.
HazardNot foundNot yet checked
Not found
Not foundWe found no source for this wire.
Trailer auxiliary powerPositive +Not yet checked
Light Blue
Peterbilt trailer and body builder lamp wiringABS power or auxiliary feed for a trailer. Peterbilt says it can be battery powered or switched, so meter it.
Vehicle speedNot foundNot yet checked
Not found
Not foundPeterbilt says the speed sensor wiring may not be spliced.
J1939 dataDataNot yet checked
Yellow (high)
Green (low)
Twisted pairs. The data bus connector is at the left rear of the enginePeterbilt warns not to cut or tap into the green and yellow twisted pairs. Use the diagnostic port for data.
Source: Peterbilt's medium duty body builder manual (July 2017). A constant wire, spare circuits, fuse positions, reverse, doors, parking brake and speed wires were not found.
Which years share wiring with the 2014 Peterbilt 325, 330, 337 and 348?
This page2014Models 325, 330, 337 and 348.
Same wiring2013, 2015, 2016, 2017Peterbilt's July 2017 manual covers trucks with 2013 emissions engines, the first with the multiplexed dash. Peterbilt says a 2013 or newer diesel chassis can be picked out by its diesel exhaust fluid gauge.
Not this page2012 and older, 2018 and newer, and the 535 to 548Peterbilt sends you to the dealer for trucks before 2013. No later edition was found for 2018 to 2021. The 535, 536, 537 and 548 have a new electrical system.
Where are the fuse boxes and ground points on a 2014 Peterbilt 325, 330, 337 and 348?
InteriorFuse box behind a corner cover in the left side foot wellThe operator manual calls it behind the driver side kick panel, below the ignition switch. The control unit for the dash is behind the center console.
OutsideData bus connector at the left rear of the engineWith the 270 amp alternator, Peterbilt mounts a mega fuse in the battery box for body power.
Ground pointsGround stud, lower outboard driver side of the firewallAt the cover plate. Peterbilt says to tie body grounds here.
From the Peterbilt body builder manual and the 2017 operator manual. The fuse panel label is a picture we could not read, so no fuse position is given.
Where is the 9-pin diagnostic port on a 2014 Peterbilt 325, 330, 337 and 348?
9-PIN
Diagnostic port9-pin diagnostic port: below the dash, left of the steering wheelPlug-in GPS trackers and J1939 devices connect here.
Common questions about 2014 Peterbilt 325, 330, 337 and 348 wiring
What wire is ignition on a 2014 Peterbilt 325, 330, 337 and 348?
Orange at the remote PTO connector, 12-pin, on the engine harness (optional), pin 7, wire label ORN1229. Ignition power for remote PTO controls. Meter it before you tap it.
Where is the brake wire on a 2014 Peterbilt 325, 330, 337 and 348?
Red (positive +) at the peterbilt trailer and body builder lamp wiring. Stop lamps. Meter it before you tap it.
Which years share wiring with the 2014 Peterbilt 325, 330, 337 and 348?
2013, 2015, 2016, 2017. Peterbilt's July 2017 manual covers trucks with 2013 emissions engines, the first with the multiplexed dash.
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