Bulletin No.:

Service Bulletin

Date:

17-NA-166
September, 2019

TECHNICAL
Subject:

Rough Idle in Drive
This Bulletin replaces PIP5211F. Please discard PIP5211F.

Brand:

Model:

Cadillac

Chevrolet

GMC

VIN:
to

Escalade
Models

2015

2019

Silverado

2014

2018

Silverado LD

2019

2019

2015

2019

Sierra

2014

2018

Sierra
Limited

2019

2019

Yukon
Models

2015

2019

Suburban
Tahoe

GMC

Model Year:
from

from

Engine:

Transmission:

L83, L86, LV1,
LV3 (4.3L,
5.3L, 6.2L)

All

to

Involved Region or Country

North America and N.A. Export Regions

Condition

Some customers may comment about a rough idle and/or vibration at idle in Drive.
This condition may be most noticeable following extended driving, after hard
acceleration, while idling at a stop in Drive.
May feel like a lopey or lumpy idle, or may be described as a low idle.
This condition will not be present in Park or Neutral. (There have been a few cases for
rough idle in Reverse.)
Note: There will not be any DTCs with this concern.

Copyright 2019 General Motors LLC. All Rights Reserved.

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September, 2019

Bulletin No.: 17-NA-166

Cause

4787059

This concern may be caused by ground out (1) within one or both engine mounts.
Important: Familiarize yourself with this entire bulletin before proceeding to ensure you
are diagnosing and focusing on the correct issue by frequency measured with Pico
scope.
Perform PICO analysis, refer to the Service Procedure section below.

Correction

⇒ If the rough idle / vibration concern frequency is E1.5 in the horizontal /
lateral direction with Pico sensor mounted in seat track as indicated below –
continue with steps to install updated design engine mounts and settle both
engine and trans mounts to reduce amplitude (mg) / eliminate ground out
within the engine mounts for vehicles built prior to engine mount breakpoint.
For vehicles built after breakpoint, follow Shimming Procedure for Engine
Mount Vibration/Grounding after Mount Replacement.
Important: The updated engine mounts are designed to reduce internal ground out,
primarily E1.5. These mounts along with engine and trans mount settling will typically
reduce amplitude at the seat track to 2 mg or less.
Note: The 6.2L engine has a characteristic E1 which can be felt and may be described
as a lopey idle. V-8 engine firing frequency produces E4 which will typically be very low
frequency at the seat track. Do not confuse 6.2L E1 characteristic (not caused by mount
ground-out), with E1.5 normal idle characteristics being transmitted into the truck via
ground-out through the engine mounts.

Service Procedure
Initial Setup / Duplication / Evaluation:
Measure the vibration disturbance using the vibration
analyzer, CH-51450-A (Pico Oscilloscope), to qualify
whether the issue frequency is E1.5 as opposed to E1
or E4.
Note: If using a single-axis pico sensor, mount and test
both vertically and horizontally – E1.5 rough idle
vibration will usually be horizontal / lateral at the seat
track.

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Bulletin No.: 17-NA-166

September, 2019

Page 3

If the E1.5 disturbance measures approximately 2 mg
or lower using the Pico tri-axis sensor as indicated –
the vehicle is considered acceptable.
1. Place tri-axis pico sensor on the inboard seat track
forward-most location to record measurement of
the rough idle vibration concern.
Note: Most rough idle in Drive concerns are
temperature dependent and can be difficult to re-create
at times.

4532456

(TA183 single axis pico sensor shown / TA143 is tri-axis
sensor)
Add E1.5 to the displayed data and turn Off T and P
related data (under Add Vibration in Pico) since issue
occurs with vehicle stationary.

2. With A/C On, perform several short heavy launch
events from stop to stop to bring the temperatures
back up while attempting to re-create the rough
idle vibration in Drive with Pico sensor placed on
inboard seat track; while the vibration is active –
Record Pico reading. This method seems to
provide better results than extended test drives.
3. If the Pico reading for E1.5, with vibration active, at
the inboard forward seat track location measures
approximately 2 mg or higher – continue following
steps in this bulletin to install updated engine
mounts and perform the engine/trans mount
settling process.
4. If the Pico reading for E1.5, with vibration active, at
specified seat track location measures close to
2 mg or less – investigate other sources of the
rough idle / vibration concern using SI diagnostics.

Install Updated Engine Mounts and Engine/
Trans Mount Settling Process
For Vehicles Built Prior to:
SUV - February 2, 2017
V-6 PU - March 15, 2017
V-8 PU - March 22, 2017

4534309

Note: Amplitude (mg) readings from a single-axis pico
sensor will be approximately 10% lower than with a
tri-axis sensor. For example, a reading of 4 mg using a
tri-axis sensor, would likely measure as about 3.6 mg
on a single-axis sensor.
If the disturbance frequency measures at the seat track
as E1.5 with amplitude of approximately 2 mg or higher
using a tri-axis sensor, continue with steps in this
bulletin to reduce the amplitude (mg) of the
disturbance, then exercise the vehicle and re-measure
using Pico to determine level of improvement.

Important: For any engine mount to frame bolts
removed during this process. Replace the engine
mount to frame bolts with NEW bolts.
Important: Do Not use Impact wrenches when
tightening the engine mount to frame bolts, or damage
to threads in the frame may result.
Important: Both LH and RH engine mounts need to be
seated to the vehicle frame At The Same Time to help
ensure best alignment.

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September, 2019

Bulletin No.: 17-NA-166

5030893

Summarized below are key notes for engine mount
replacement for rough idle:
1. Replace both engine mounts (1). Refer to Engine
Mount Replacement – Left and Right Engine
Mount Replacement in SI.
2. Install but do NOT tighten the mount to frame bolts.
3. Settle all mounts as follows:
3.1. Ensure the engine mount to frame bolts on
both LH and RH sides are loosened a couple
turns.
3.2. Ensure, the transmission/transfer case mount
to frame crossmember nuts are loosened a
couple of turns.
3.3. Have assistant set park brake and apply base
brake.
3.4. Have assistant turn Traction Control Off, and
brake torque in Drive and Reverse with the
engine at operating temperature, then place
in Neutral and turn engine Off.

Bulletin No.: 17-NA-166

September, 2019

Page 5

5318277

3.5. In Neutral, with engine Off, using Only Hand
Tools, torque all the new engine mount to
frame bolts (1) in sequence shown;
3.5.1. 50 Nm (37 lb ft)
3.5.2. Final Pass 65 degrees
3.6. Torque the transmission/transfer case mount
to crossmember nuts to 55 Nm (41 lb ft).
4. Re-evaluate the rough idle vibration – repeating
steps 1-4 under Initial Set-up / Duplication /
Evaluation.
If the E1.5 idle vibration at inboard seat track forward
location has been reduced to 2 mg or less – the vehicle
is considered acceptable.
If a different frequency other than E1.5 is now elevated,
for example E4, then most likely one of the mounts is
bound. Carefully repeat the mount settling process for
the engine and trans mounts, then re-evaluate.

Shimming Procedure for Engine Mount
Vibration/Grounding after Mount Replacement
For Vehicles Built After to:
SUV - February 2, 2017
V-6 PU - March 15, 2017
V-8 PU - March 22, 2017
Important: For any engine mount to frame bolts
removed during this process. Replace the engine
mount to frame bolts with NEW bolts.
Note: Idle vibration caused by ground-out within an
engine mount may be able to be turned off/on with a
single bolt location. Shimming that bolt location may
greatly reduce the vibration. In some cases, a
combination of bolt location shimming may be needed.
1. With the aid of an assistant, run vehicle in stall with
the parking brake set and base brake applied, in
Drive, monitoring E1.5 on Pico at inboard seat
track, with idle vibration active, perform the
following:

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September, 2019

Bulletin No.: 17-NA-166

5318277

Important: Do Not use Impact wrenches when
tightening the engine mount to frame bolts, or damage
to threads in the frame may result.
2. Beginning with RH side, loosen the engine mount
to frame bolts one at a time a few turns to release
clamp load beginning with rear bolt at position 6,
front bolt at position 5 and the middle bolt at
position 4.
⇒ Verify if idle vibration was significantly reduced
or eliminated when the bolts were loosened.
3. Torque bolts to specifications in order and validate
if the vibration returns.
4. Repeat the process on the LH mount starting at the
rear bolt at position 3, front bolt at position 2 and
the middle bolt at position 1.
• If idle vibration Does Not return when the RH or
LH engine mount bolts are re-torqued to
specifications, remove the old bolts and
discard. Replace the bolts with new ones.
• If idle vibration Does return, proceed with
procedure.

Bulletin No.: 17-NA-166

September, 2019

Page 7

5164611

Note: Pause after loosening any of the mount bolts
during these steps to determine the effect of the idle
vibration on the Pico, at the seat track while making
note of effect from each bolt location.
5. Beginning with RH side, loosen the engine mount
(1) to frame bolts one at a time a few turns to
release clamp load.
6. Remove the position 5 and 6 bolts (2),
7. Utilizing a jack with a block of wood, carefully raise
the engine.
Note: For spacer washers mild steel is recommended,
no stainless; it may be necessary for some locations to
use a small amount of adhesive such as ‘dum-dum’ to
hold spacer in place.
8. If idle vibration was significantly reduced, add a
spacer washer (3) approximately 2.5 mm thick
between the engine mount and frame at position 5
and 6.
9. Install old engine mount to frame bolts.
10. Lower the engine.
11. Torque the bolts to specifications to validate if the
vibration returns:
• If idle vibration could be turned off with
shimming one side, remove the old bolts and
discard. Replace the bolts with new ones.
• If idle vibration returns. Remove the shims and
repeat the process for the LH mount.
12. Tighten the affected engine mount to frame bolts in
sequence, to specification.

Re-evaluate the rough idle vibration by repeating steps
6-9 under Initial Setup / Duplication / Evaluation.
⇒ If the E1.5 idle vibration at inboard seat track
forward location has been reduced to less than
3 mg, determine with customer if condition is now
acceptable.
If there was not a single bolt location on the RH or LH
mount which could turn the idle vibration off/on,
shimming will be necessary for 2 or 3 bolt locations on
one side.
⇒ Go back to the 2 bolts with greatest effect recorded
on vibration reduction on one side and shim those
bolts.

Fine Tuning - Pico Sensor on Mounts (If
Needed)
Note: It is difficult to lower amplitude of E1.5 idle
vibration at the seat track to about 2.5 mg or lower.
Many customers are satisfied with approximately 3 mg
or less. Some customers may not be satisfied until the
idle vibration is brought below 3 mg, closer to 2.5 mg.
1. While the tri-axis sensor is mounted on the inboard
seat track forward most location (Channels A-C),
Add a second Pico sensor tri-axis or single plane
using Channel D.
2. Place the added Pico sensor on the middle engine
mount bolt head, beginning with RH side.

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September, 2019

3. For Pico readings from the mount, focus on
Vertical E1.5. (suggest removing lateral and fore/
aft channels from display and removing E1 and E4
from display).
4. While the idle vibration is active, record the E1.5
amplitude (mg).
5. Repeat steps 1-4 for LH side while the idle
vibration is active and compare readings.
6. Focusing on the side with highest E1.5 amplitude
(mg), perform the following:
6.1. Place the added Pico sensor on the engine
mount rear bolt head.
6.2. While the idle vibration is active, record the
E1.5 amplitude (mg).
6.3. Move sensor to middle bolt head and repeat.
6.4. Move sensor to front bolt head and repeat.
⇒ if a spacer washer is not already in position,
add a spacer washer approximately 2.5 mm
thick between the engine mount and frame
attachment at the bolt location with the highest
recorded E1.5 amplitude (mg).
7. Re-evaluate the rough idle vibration repeating
steps 1-4 under Initial Setup / Duplication /
Evaluation:
• If the E1.5 idle vibration at inboard seat track
forward location has been reduced below 3 mg,
determine with customer if condition is now
acceptable.
• If the E1.5 idle vibration at inboard seat track
forward location has not been reduced below
3 mg, if a spacer washer is not already in
position, add a spacer washer, approximately
2.5 mm think between the engine mount and
frame attachment at the bolt location with the
second highest recorded E1.5 amplitude (mg).
(Leave the spacer washer at the highest
recorded bolt location.)
8. Re-evaluate the rough idle vibration by repeating
steps 1-4 under Initial Setup / Duplication /
Evaluation.

Bulletin No.: 17-NA-166

Parts Information
Causal
Part

Description

Part
Number

Qty

X

Mount, Engine

Refer
to EPC

1 Set

Warranty Information
For vehicles repaired under the Powertrain coverage,
use the following labor operation. Reference the
Applicable Warranties section of Investigate Vehicle
History (IVH) for coverage information.
Labor
Operation

Description

Labor Time

4081688*

Perform Pico Scope Idle
Vibration Measurement

0.4 hr

4086928*

Engine Mount Shimming
Procedure - One Side
Note: Time Includes Engine
and Trans Mount Settling.

1.5 hr

Add

Engine Mount Shimming
Procedure - Both Sides

0.5 hr
3.8 hr (SUV)

4081348*

Engine Mount Replacement
- Both Sides

3.1 hr (PU
V-6)
3.2 hr (PU
V-8)

*This is a unique Labor Operation for Bulletin use only.

Version

6

Modified

Revised June 6, 2017 - Updated information, moved Parts Information and Warranty
Information tables to bottom of bulletin and added Keywords.
Revised September 05, 2018 - Updated labor time information
Revised November 16, 2018 - Add Mount Shimming Procedure and Fine Tuning
sections, Added 2018 Model Year and Removed Vin Break Point.
Revised April 18, 2019 - Update Shimming Procedure section, Add build cutoff dates,
Update Engine Mount procedure, Updated Parts Information section and update the
labor time.
Revised September 11, 2019 - Added to replace the engine mount bolts in both
procedures.

Additional Keywords: PIP5211, PIP5211D, PIP5211E,
vibration
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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