reference circuit. The sensor provides the fuel pressure
signal to the ECM, which is used for Closed Loop fuel
pressure control.
Fuel Pump Driver Control Module
The K111 fuel pump driver control module is a
serviceable GMLAN module. The fuel pump driver
control module receives the desired fuel pressure
signal from the ECM and controls the fuel pump located
within the fuel tank to achieve the desired fuel pressure.
The fuel pump driver control module controls the
in-tank fuel pump by providing varying AC voltage to
the 3 phase motor inside the fuel pump.

Bulletin No.: 19-NA-091

Fuel Pump
The fuel pump is mounted in the fuel tank fuel pump
module reservoir. The fuel pump is a 3 phase electric
pump. Fuel is pumped to the high pressure fuel pump
at a pressure that is based on feedback from the fuel
pressure sensor. The fuel pump delivers a constant
flow of fuel even during low fuel conditions and
aggressive vehicle maneuvers. The fuel pump flex pipe
acts to dampen the fuel pulses and noise generated by
the fuel pump.
Fuel Pump — High Pressure
The high fuel pressure necessary for direct injection
(DI) is supplied by the high pressure fuel pump. The
high pressure fuel pump is mounted on the rear of the
engine under the intake manifold and is driven by a
tri-lobe cam on the camshaft. The high pressure fuel
pump also regulates the fuel pressure using an actuator
in the form of an internal solenoid-controlled valve.
Fuel Tank Fuel Pump Module
The electric turbine style fuel pump attaches to the fuel
tank fuel pump module inside the fuel tank and supplies
fuel through the fuel feed pipe to the high pressure fuel
pump. The fuel tank fuel pump module contains a
reverse flow check valve. The check valve maintains
fuel pressure in the fuel feed pipe in order to prevent
long cranking times. The fuel tank fuel pump module
consists of the following major components:
• Fuel Level Sensor: The fuel level sensor
consists of a float, a wire float arm, and a ceramic
resistor card. The position of the float arm
indicates the fuel level. The fuel level sensor
contains a variable resistor which changes
resistance in correspondence with the position of
the float arm. The ECM monitors the signal circuit
of the fuel level sensor in order to determine the
fuel level and sends the information to the
instrument panel cluster to control the fuel gauge.
• Fuel Pump and Reservoir Assembly
• Pressure Relief Regulator Valve: The pressure
relief regulator valve replaces the typical fuel
pressure regulator used on a mechanical
returnless fuel system. The valve is closed during
normal vehicle operation. The pressure relief
regulator valve is used to vent pressure during hot
soaks and also functions as a fuel pressure
regulator in the event of the fuel pump driver
control module defaulting to 100% commanded
output of the fuel pump.
• Fuel Strainer
• Primary Jet Pump: The primary jet pump is
located in the fuel tank fuel pump module. Fuel
pump flow loss, caused by vapor expansion in the
pump inlet chamber, is diverted to the primary jet
pump through a restrictive orifice located on the
pump cover. The primary jet pump fills the
reservoir of the fuel tank fuel pump module.

Bulletin No.: 19-NA-091

June, 2019

Fuel Rail Assembly
The fuel rail assembly attaches to each cylinder head.
The fuel rail distributes high pressure fuel to the fuel
injectors. The fuel rail assembly consists of the direct
fuel injectors and the fuel rail pressure sensor. The fuel
rail pressure sensor transmits fuel pressure and
temperature information by serial data using the
Society of Automotive Engineers (SAE) J2716 Single
Edge Nibble Transmission (SENT) protocol.

Page 7

Engine 6.6L V8 — RPO L5P
Overview

Fuel Injectors
The fuel injector assembly is an inside opening
electrical magnetic injector. The injector has six
precision machined holes that generate a cone shaped
oval spray pattern. The fuel injector has a slim
extended tip in order to allow a sufficient cooling jacket
in the cylinder head. The fuel injectors are mounted in
the cylinder head beneath the intake ports and spray
fuel directly into the combustion chamber. Direct
injection requires very high fuel pressure due to the fuel
injector's location in the combustion chamber.

Engine Oil — 6.6L Gasoline
Specification

5122972

Typical view of the Duramax® 6.6L V8 — RPO L5P
This is a turbocharged diesel engine produced by
DMAX which is a joint venture between GM and Isuzu
in Moraine, Ohio for use in the new 2500HD, 3500HD
pickup trucks and other GM vehicles.
Engine Features and Specifications
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5108021

Use full synthetic engine oils that meet the dexos®1
APPROVED - GEN 2 specification. Engine oils that
have been approved by GM as meeting the dexos®1
specification are marked with the dexos®1
APPROVED - GEN 2 logo.
Viscosity Grade
Use SAE 5W-30 viscosity grade engine oil for the 6.6L
V8 gasoline engine. In an area of extreme cold, where
the temperature is colder than −20°F (−29°C), use SAE
0W-30 oil. An oil of this viscosity grade will provide
easier cold starting for the engine at extremely cold
temperatures.

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Bore/Stroke: 4.055-inches (103 mm) /
3.8976-inches (99 mm).
Compression Ratio: 16.0:1
Cooling System: Cooling system capacity is
30.8 qt (29.15 L).
Connecting Rods: The connecting rods are
one-piece hot forged steel. The connecting rods
and caps are of a fractured split design to improve
durability and reduce internal friction. The
connecting rod small end is tapered cut for
reduced weight and improved durability.
Crankshaft: The crankshaft is a forged steel
design with five main bearings. Crankshaft thrust
is controlled by the number 5 bearing.

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June, 2019

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Bulletin No.: 19-NA-091
amount of oxygen entering the engine. With less
oxygen in the air/fuel mixture, the combustion
pressures are reduced, and as a result,
combustion temperatures are decreased,
restricting the formation of NOx. Exhaust gas
recirculation is water cooled for improved
reduction in NOx emissions.
Exhaust Manifold: Cast nodular iron with steel
pipe extension.
Firing Order: 1-2-7-8-4-5-6-3
Fuel System: Direct injection (DI) with
high-pressure common rail. In the diesel engine,
air alone is compressed in the cylinder. Then, after
the air has been compressed, a charge of fuel is
sprayed into the cylinder and ignition occurs, due
to the heat of compression.

4663083

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Cylinder Block: The engine block utilizes a deep
skirt design for increased rigidity. The cylinders
are positioned in a 90 degree "V" orientation with
the number one cylinder being the right front. The
block is induction hardened for increased
durability. The crankshaft bearing caps are
cross-bolted to enhance structural rigidity.
Cylinder Head: The cylinder heads are made of
aluminum for lighter weight and rapid heat
dissipation. There are 4 valves per cylinder and
the ports are of a high swirl design for improved
combustion. The cylinder head gaskets consist of
an all steel laminated construction.
Engine Covers: There is a front engine cover
and a flywheel housing, both are made of
aluminum. The full bell flywheel housing is cross
bolted to the upper oil pan. The flywheel housing
also provides a crossover passage for engine
coolant. The front engine cover houses the gear
train and provides a mounting surface for the
cooling fan pulley assembly.
Engine Oil Capacity with Filter: Capacity is
10 qt (9.5 L).
EGR System: The EGR system is used to reduce
the amount of nitrogen oxide (NOx) emission
levels caused by high combustion temperatures.
At temperatures more than 1,371°C (2,500°F),
oxygen and nitrogen combine to form NOx.
Introducing small amounts of exhaust gas back
into the combustion chamber displaces the

5152404

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Fuel Type: GM recommends the use of TOP
TIER Diesel Fuel to keep the engine clean and
reduce engine deposits. Use Ultra-Low Sulfur
Highway Diesel Fuel and/or B20 biodiesel. Fuels
with a biodiesel content up to 20% by volume may
be used (e.g., named B20). Always look for the
TOP TIER Diesel Fuel Logo at the fuel dispenser.
– DO NOT use diesel fuel with more than 15 ppm
sulfur.
– DO NOT use off-highway diesel fuel, also known
as off-road diesel fuel.
Glow Plugs: The engine utilizes eight ceramic
glow plugs. Compared to conventional glow plugs,
ceramic glow plugs enable greater efficiency
through higher temperature capability and faster
preheating time. However, ceramic glow plugs are
much more sensitive to damage than conventional
glow plugs. Damage can occur to the glow plug
and not be visible, causing future engine failure.
Therefore, ceramic glow plugs are considered
one-time-use. Be sure to discard and replace with
NEW whenever a ceramic glow plug is removed
from the cylinder head. If the cylinder head is ever
removed with the ceramic glow plugs, the ceramic
glow plugs must all be replaced with new.

Bulletin No.: 19-NA-091

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June, 2019

Whenever installing a new ceramic glow plug,
clean the glow plug bore with a proper tool as
outlined in the service procedure. Carbon build-up
in the glow plug bore can damage the ceramic
glow plugs.
Horsepower: SAE-certified 445 horsepower
(332 kW).
Torque: SAE-certified 910 lb-ft (1,234 Nm).
Intake Airflow Valve: The intake airflow valve is
a throttle plate actuator and is used to achieve
high exhaust gas recirculation rates. It increases
the pressure difference between exhaust and
intake so that the appropriate exhaust quantity
can be mixed with the intake air.
Maximum Braking Speed: 4,800 RPM.
Maximum Powered Speed: 3,450 RPM.
Oil Cooler: The oil cooler lowers engine
temperature by cooling the oil with engine coolant.
Engine coolant is directed from the water pump to
the oil cooler by a coolant tube. The oil filter
attaches directly to the oil cooler.
Oil Pump: The oil pump is gear driven directly
from the crankshaft. The oil pump drive gear is a
slip fit to the crankshaft.
Piston: The pistons are a full-floating design. The
piston pins are a slip fit in the bronze bushed
connecting rod and are retained in the piston by
round wire retainers. The pistons have a piston
cooling oil channel cast inside. These cooling oil
channels utilize an oil jet located at the bottom of
the cylinder bore to direct oil into the piston
channel. There are two compression rings and
one oil control ring. There is a groove machined
into the pistons between the first and second
compression rings. This groove reduces
compression ring leakage by providing an empty
space for expanding gases, reducing the
combustion gas pressure on the second
compression ring.
Turbocharger: The turbocharger is water cooled
for improved durability. It is a variable vane style.
The pitch of the turbine vanes can be changed by
ECM command to meet varying conditions.
Upper Oil Pan: A single piece cast aluminum
upper oil pan contributes to crankshaft and block
rigidity while reducing overall weight.
Valvetrain: The engine utilizes a mechanical
roller lifter for valve operation. One rocker arm
operates two valves simultaneously through a
valve bridge.
Water Pump: The water pump is gear driven for
improved reliability.

Page 9

Duramax® After-Run Feature
A new after-run feature, specifically engineered for use
following a demanding towing situation is an additional
new technology for the Duramax engine. The after-run
allows the engine to keep running for up to 15 minutes
to allow it to cool down using the fan and circulating the
engine coolant. If the driver puts the truck in P when an
after-run situation is needed, an alert will appear on the
DIC directing them to keep the engine running for cool
down. Should the driver choose to ignore the message
and exit the vehicle, the truck will restart on its own via
remote start mode for cool-down. At that point the
customer can walk away and the truck will turn itself
OFF when the engine reaches an acceptable
temperature.
Duramax® Cooling System
Helping cool the Duramax® engine is a massive
28-inch (71 cm) diameter fan with variable fan speed,
which is 2.5-inches (6.35 cm) larger than the current
fan. The ECM controls the fan speed by sending a
pulse width modulated (PWM) signal to the cooling fan
control module. The cooling fan control module varies
the voltage drop across the cooling fan motor in relation
to the PWM signal, which allows the cooling fan to
operate at variable speeds.
Elevated Idle
The engine has a cold temperature high idle feature
which elevates the engine idle speed from base idle to
approximately 1,050 to 1,100 RPM when outside
ambient temperatures are colder than 32°F (0°C), and
the engine coolant temperature (ECT) is colder than
150°F (65°C). This feature enhances heater
performance by increasing the ECT faster.
Engine Coolant Heater
The coolant heater operates using 110 V alternating
current from an external power source and is designed
to warm the coolant in the engine block area for
improved starting in weather conditions that are colder
than 0°F (−18°C). Vehicles with an engine block heater
should be plugged in at least four hours before starting.
An internal thermostat in the plug-end of the cord may
exist, which will prevent engine coolant heater
operation at temperatures warmer than 0°F (−18°C).
The coolant heater also helps reduce fuel consumption
when a cold engine is warming up. The unit is equipped
with a detachable AC power cord. A weather shield on
the cord is provided to protect the plug when not in use.
Exhaust Brake
The Duramax® / Allison® combination incorporates an
integrated engine exhaust brake, which leverages the
engine’s backpressure and the Heavy Duty’s driveline
components to help control the speed of the truck and
trailer while descending, reducing the need to use
service brakes on long, steep grades. The exhaust
brake is also tied to the cruise control system, allowing
a set speed to easily be maintained, even over hilly
terrain.

Page 10

June, 2019

Bulletin No.: 19-NA-091

Fuel System Diagram
Fuel System Diagram — RPO L5P

5294832

Legend
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)

Auxiliary Fuel Tank (Equipped with
RPO N2N)
Fuel Filter Assembly with Water in Fuel
Sensor
E11A Fuel Heater/Water in Fuel Sensor
B48 Fuel Temperature Sensor
B47 Fuel Pressure Sensor
Q67 Exhaust Aftertreatment Fuel Injector
B47B Fuel Rail Pressure Sensor
Fuel Injection Fuel Rail Assembly
Q18B Fuel Rail Pressure Regulator 2

Fuel Tank — Auxiliary
For vehicles equipped with dual fuel tanks, the auxiliary
fuel tank is located in the rear of the vehicle. The fuel
tank is held in place by 2 metal straps that attach to the
frame. The fuel tank is molded from high density
polyethylene.
Fuel Filter Assembly
The fuel filter assembly is located near the left frame
rail and contains the following components: fuel filter/
water separator, fuel heater, fuel temperature sensor,
water in fuel sensor.

(10)
(11)
(12)
(13)
(14)
(15)
(16)
(17)

Q18A Fuel Pressure Regulator 1
(Located in Fuel Injection Pump)
G18 High Pressure Fuel Pump
Q17 Fuel Injector(s)
Fuel Cooler
Fuel Tank — Primary
G12A Fuel Pump — Primary
G12B Fuel Pump — Secondary
(Equipped with RPO N2N)
K111 Fuel Pump Driver Control Module

Fuel Heater
The fuel heater is controlled by the ECM. When the
temperature of the fuel is less than a calibrated value,
the ECM will command the fuel heater relay ON. When
the relay is ON, battery voltage is supplied to the fuel
heater to assist in cold weather operation.
Fuel Temperature Sensor
The fuel temperature sensor is a thermistor that is
located in the fuel filter assembly. The ECM monitors
the fuel temperature sensor through the fuel pump
driver control module in order to calculate the
temperature of the fuel entering the fuel injection pump.

Bulletin No.: 19-NA-091

June, 2019

Page 11

Fuel Pressure Sensor
The fuel pressure sensor is located in the fuel feed
pipe. The fuel pressure sensor monitors the fuel
pressure in the fuel line. The ECM monitors the voltage
signal from the fuel pressure sensor. The sensor
provides a fuel pressure signal to the ECM, which is
used to provide fuel pressure control.

High Pressure Fuel Pump
The high pressure fuel pump is a mechanical pump.
The high pressure fuel pump is located at the front of
the engine below the intake manifold. The high
pressure fuel pumps provides high pressure fuel to the
fuel rail at a specified pressure regulated by the fuel
pressure regulators.

Exhaust Aftertreatment Fuel Injector
The exhaust aftertreatment fuel injector, also known as
an indirect fuel injector is located on the passenger side
frame rail. The exhaust aftertreatment fuel injector is
used to inject fuel into the exhaust system to generate
the required heat needed by the diesel oxidation
catalyst to function properly.

Fuel Injectors
A fuel injector is a solenoid device, controlled by the
ECM, that meters pressurized fuel to a single engine
cylinder. Fuel from the fuel injector tip is sprayed
directly into the combustion chamber on the
compression stroke of the engine. The fuel injectors are
located above each cylinder and deliver fuel directly
into the cylinder. Each injector has a high pressure fuel
pipe from the fuel rail and a return line.

Dual Fuel Rail Pressure Sensor
The fuel rail pressure sensor is a dual analog sensor
that provides two fuel rail pressure signals to the ECM
and is located in the end of the fuel rail assembly. The
ECM provides a 5 V reference voltage on the 5 V
reference circuit and ground on the low reference
circuit. The ECM receives a varying signal voltage on
both the fuel rail pressure sensor and fuel rail pressure
sensor 2 signal circuits. The ECM monitors the voltage
on both of the fuel rail pressure sensor circuits and
compares the values to determine if the sensors are
accurate. When the fuel pressure is high, the fuel rail
pressure sensor signal voltage is high and the fuel rail
pressure sensor 2 signal voltage is low. When the fuel
pressure is low, the fuel rail pressure sensor signal
voltage is low and the fuel rail pressure sensor 2 signal
voltage is high.
Fuel Rail Assembly
The left and right fuel rails are attached to the cylinder
heads. The fuel rails distribute pressurized fuel to the
fuel injectors through the fuel lines.
Fuel Pressure Regulator 1
The ECM controls the fuel rail pressure using two pulse
width modulated fuel rail pressure regulators. Fuel
pressure regulator 1 is located in the fuel injection
pump and meters the amount of fuel that enters the
high pressure side of the pump. From the high pressure
pump, the fuel moves to the fuel rail through a high
pressure steel line. The fuel rail distributes high
pressure fuel to all 8 fuel injectors.
Fuel Pressure Regulator 2
The ECM controls the fuel rail pressure using two pulse
width modulated fuel rail pressure regulators. Fuel
pressure regulator 2 is located on the rear of the driver
side fuel rail and meters the amount of fuel being
returned to the fuel tank. The ECM varies the pulse
width modulated voltage to the fuel pressure regulator 2
to relieve excessive fuel pressure which returns to the
fuel tank. When the ignition is OFF, fuel pressure
regulator 2 opens to bleed off the pressure in the
fuel rail.

Fuel Cooler
The fuel cooler is located under the vehicle. The
returning fuel flows through the cooler in order to
reduce the fuel temperature before returning it to the
vehicle’s fuel tank.
Fuel Tank — Primary
The primary fuel tank is located on the left side of the
vehicle. The fuel tank is held in place by 2 metal straps
that attach to the frame. The fuel tank is molded from
high density polyethylene.
Fuel Pump — Primary
The primary fuel pump is mounted in the primary fuel
tank module reservoir.
Fuel Pump — Secondary
The fuel transfer pump is located in the auxiliary (rear)
fuel tank, (if equipped with N2N).
Fuel Pump Driver Control Module
The fuel pump driver control module is located under
the vehicle, mounted to the bracket above the spare
tire. If this component is replaced, the Fuel Pump Driver
Control Module Configuration must be performed.
Water in Fuel Sensor
The water in fuel sensor monitors for the presence of
water in the diesel fuel. When water is present, the fuel
pump driver control module detects low voltage on the
signal circuit and sends a message to the ECM. The
ECM sends a serial data message to the instrument
panel cluster to display the WATER IN FUEL SERVICE
REQUIRED message.

Page 12

June, 2019

Bulletin No.: 19-NA-091

Exhaust Aftreatment System
Emission Control System Architecture — RPO L5P

4863779

Legend
(1)
(2)
(3)
(4)
(5)
(6)
(7)

E41 ECM w/Baro Sensor