Various Engine Noises During Cold Start and Warm Engine Operation – 2014-2020 Cadillac Chevrolet GMC

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Service in
Bulletin No.: 14-06-04-004F
Date: March, 2020

INFORMATION
Subject: Various Engine Noises During Cold Start and Warm Engine Operation

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

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 2020 Model Year to certain vehicles. Please discard
Corporate Bulletin Number 14-06-04-004E.
Information For Why New Engine Technologies Are Generating Noises
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.
Direct Injection (DI) / High Pressure Fuel Pump / Fuel Injectors
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 and the 6.2L V8.
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 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.
WE SUPPORT VOLUNTARY TECHNICIAN
CERTIFICATION

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NHTSA ID Number: 10112799

Manufacturer Communication Number: 14-06-04-004C

Summary

This informational bulletin provides information on what some possible causes could be contributing to various engine noises during cold start and warm engine operation

1 Associated Document

Manufacturer Communications

Bulletin No.: 14-06-04-004C
Date: Mar-2016

https://www.nhtsa.gov/recalls?nhtsaId=10112799

MC-10112799-9999.pdf 93.575KB

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NHTSA ID Number: 10140358

Manufacturer Communication Number: 14-06-04-004B

 

Summary

This information bulletin provides additional information to the technician on how to diagnose possible normal engine noise during a cold star and a warm engine operation.

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1 Associated Document

Manufacturer Communications

File in Section: 06 – Engine
Bulletin No.: 14-06-04-004B
Date: July, 2014

https://www.nhtsa.gov/recalls?nhtsaId=10140358

MC-10140358-9999.pdf 495.542KB

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