17NA166 Service Bulletin/Repair Instructions

Service Bulletin
Bulletin No.:
17-NA-166
Date:
April, 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.
Page 2
April, 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.
4532459
Bulletin No.: 17-NA-166
April, 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

Note: For any engine mount to frame bolts and engine

mount to engine block bolts removed during this

process – clean bolt threads using denatured alcohol or

equivalent; then apply threadlocker or equivalent to the

bolt threads. Refer to Adhesives, Fluids, Lubricants,

and Sealers.

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: 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.
Page 4
April, 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
April, 2019
Page 5
5318277
3.5. In Neutral, with engine Off, using Only Hand

Tools, torque all 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. Clean bolt threads using

denatured alcohol or equivalent; then apply

threadlocker or equivalent to the bolt threads. Refer to

Adhesives, Fluids, Lubricants, and Sealers. Important.

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:
Page 6
April, 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, no further work is required.

• If idle vibration Does return, proceed with

procedure.
Bulletin No.: 17-NA-166
April, 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. Apply threadlocker or equivalent to the threads of

the engine mount to frame bolts. Refer to

Adhesives, Fluids, Lubricants, and Sealers.

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, no further work is required.

• 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.
Page 8
April, 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
5
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.
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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