POWER TAKE-OFF (PTO)
Peterbilt Motors Company 8-18
CHASSIS HARNESS WIRING
W/ Eaton automated transmissions:
For Eaton Ultrashift Plus and Advantage automated transmissions, the transmission ECU requires an
isolated PTO engaged signal. The Eaton PTO relay (P27-1151) is used to isolate the PTO engaged
signal to the transmission ECU. The Eaton PTO relay coil receives 12V IGN power from fuse E_E9 body
IGN from pin 7 of the engine harness PTO/remote throttle connector (P111). PTO engage circuit has a
path to ground. This ground path allows current to flow through the Eaton PTO relay coil. When the relay
is active pins 34 and 18 on the transmission controller are shorted providing the PTO engaged signal to
the transmission ECU.
W/ MX engines:
The MX PTO relay is required to convert the low PTO engaged signal to a high signal for the MX ECU.
The MX PTO relay (P27-1151) is used to convert this signal. The MX PTO relay coil receives 12V IGN
power from fuse E_E9 body IGN from pin 7 of the MX engine harness PTO/remote throttle connector
(P111). When a PTO engages the PTO engage circuit has a path to ground. This ground path allows
current to flow through the MX PTO relay coil. When the MX PTO relay is active the MX ECU receives a
high input signaling that the PTO is engaged.
W/ Namco split shaft PTO/transfer case units:
Note: since the Namco option uses relays in the same position as the snow plow option these options
cannot be called out together. For chassis with a Namco split shaft PTO/transfer case several
configurations are available which require up to three relays to convert the engaged signal to drive the
PTO, pump mode and front axle declutch warning lamps. The three possible clutch configurations: rear
axle & front axle, rear axle & PTO, rear axle, PTO and front axle.
PTO:
When the PTO is not engaged the Namco sensor sends a high signal on pin 2 (J195) energizing
the Namco PTO relay coil (P27-1150). When the Namco PTO relay is energized no signal leaves
the relay. When the PTO is engaged the sensor output goes low. The Namco PTO relay coil de-
energizes and the PTO warning lamp is grounded.
Pump mode: (rear axle declutch)
When the Namco axle clutch is in road mode the Namco sensor sends a high signal on pin 4
(J195) energizing the Namco pump relay coil (P27-1150). While the Namco pump relay is
energized no signal leaves the relay. When the rear axle is declutched for pump mode the sensor
output goes low. The Namco pump relay coil de-energizes and the pump mode circuit is
grounded.
Front axle clutch:
When the Namco front axle clutch is not engaged the Namco sensor sends a high signal on pin 5
(J195) energizing the Namco front axle clutch relay coil (P27-1150). While the Namco pump relay
is energized no signal leaves the relay. When the front axle is clutched for front axle power the
sensor output goes low. The Namco pump relay coil de-energizes and the front axle clutch circuit
is grounded.
Chassis with a Namco split shaft PTO will also be provided with a 6-way connector to connect to
the Namco sensor jumper harness (J195).
