Bulletin No.:

Service Bulletin

Date:

14-06-04-004G
June, 2020

INFORMATION
Subject:

Various Engine Noises During Cold Start and Warm Engine Operation

Models:

2015-2020 Cadillac Escalade, Escalade ESV
2016-2019 Cadillac CTS
2014-2018 Chevrolet Silverado 1500
2014-2019 Chevrolet Corvette
2015-2020 Chevrolet Suburban, Tahoe
2016-2020 Chevrolet Camaro
2019 Chevrolet Silverado 1500 LD
2019 Chevrolet Silverado 1500 (New Model - 12th VIN Digit = 7)
2019 Chevrolet Silverado 1500 (New Model)
2019-2020 Chevrolet Silverado 2500/3500
2020 Chevrolet Silverado 1500
2014-2018 GMC Sierra 1500, Denali Models
2015-2020 GMC Yukon, Yukon XL
2019 GMC Sierra 1500 Limited
2019 GMC Sierra 1500 (New Model)
2019-2020 GMC Sierra 2500/3500
2020 GMC Sierra 1500
Equipped with 4.3L Engine (RPOs LV1, LV3), 5.3L Engine (RPOs L82, L83, L84), 6.2L
Engine (RPOs L86, L87, LT1, LT4, LT5) or 6.6L Engine (RPO L8T)

Attention: This bulletin also applies to any of the above models that may be Export from North
America vehicles.
This bulletin has been revised to add the 6.6L (RPO L8T) engine. Please discard Corporate
Bulletin Number 14-06-04-004F.

Information For Why New Engine
Technologies Are Generating Noises

Direct Injection (DI) / High Pressure
Fuel Pump / Fuel Injectors

The latest generation of full size trucks and utilities
incorporate a new generation of technologies not
previously seen in full size truck and utility applications.
As a result these engines generate noises during cold
start and during warm operation that owners of
previous generation multiport fuel injection (MFI)
vehicles may not be familiar with.

The new Small Block Generation 5 engine family
incorporates a new fuel system technology known as
Direct Injection (DI). With DI, fuel is injected directly into
the cylinder using a high pressure fuel system. DI
provides many benefits in improving engine efficiency.
In particular, DI improves power, torque, and most
importantly fuel efficiency. This technology is included
as standard equipment on all Generation 5 engines in
the Small Block engine family, which are the 4.3L V6,
5.3L V8, 6.2L V8 and the 6.6L V8.

Copyright 2020 General Motors LLC. All Rights Reserved.

Page 2

June, 2020

The high pressure fuel system does have unique
operating characteristics, in particular the noise
emanating from the high pressure fuel pump can result
in a subtle ticking noise that is apparent when the
vehicle is idling. The sound is more evident when
outside around the vehicle, when the hood is open or
the vehicle is operated in a drive-through. The sound
may be more noticeable during a cold start, but lessens
once the engine is warm. A slightly higher pitched
clicking sound is the fuel injectors pulsing ON and OFF
under the high fuel pressures.
These sounds are a normal characteristics of the DI
high pressure fuel system.
Another operating characteristic is a slightly longer
crank time when the engine is started. The increased
crank time is the result of the time required to build high
pressure in the fuel system before the engine starts.

Oil Pump Cold Start Rrrrp or Rasp
The oil pump design has changed from a gerotor gear
type pump to a two-stage vane type pump for fuel
economy reasons. At temperatures at or below 0°C
(32°F), or when the engine has been sitting for a few

Bulletin No.: 14-06-04-004G

hours, it is possible to have air enter the pump through
normal oil drain back. Upon startup, the owner may
hear a short “Rrrrp” or “Rasp” coming from the front of
the engine. It is most often heard during a remote start.
There is nothing wrong with the oil pump or oil system.
No repairs should be attempted for this condition.

6.2L Engine – Dry Sump Oil
System Moan
The 6.2L engine dry sump oil system may generate a
moan noise that may be heard inside the vehicle at idle
and/or low engine rpm operation for approximately the
first two minutes following a cold start. The noise
cannot be heard from the outside of the vehicle. This
noise may be more noticeable on the passenger side of
the vehicle and has been described as similar to the
sound of running water.
The dry sump oil system is hard mounted to the body of
the vehicle, and at cold start, the oil moving through the
system can transfer the noise to the body.
This is a normal dry sump oil system operating
characteristic and no repairs should be attempted.

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these
technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper
service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a
job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your
vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the
information.

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