PIT4529D Service Bulletin/Repair Instructions

Bulletin No.: PIT4529D

Published date: 03/5/2018
Preliminary Information

PIT4529D Elevated Idle/ PTO/ High Idle Are All Different Options

Models

Brand:
Model:
Model Years:
VIN:

from
Engine:
to
Transmissions:
Chevrolet
Silverado 2500/3500
2007 - 2018
All
All
All
All
GMC
Sierra 2500/3500
2007 - 2018
All
All
All
All
Supersession Statement

This PI was superseded to update the model years. Please discard PIT4529C.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition / Concern

INFORMATION ONLY:

There have been some questions regarding the differences between Elevated Idle, PTO, and High Idle.

The below information is to help provide additional information as to what each of the options are:
Elevated Idle

Is a standard option on all 6.6L Diesel Engines, which elevates the engine idle speed from base idle to 1050 RPMs when outside

temperatures are below 32°F (0°C) and the engine coolant temperature is

below 150°F (65°C). This feature enhances heater performance by raising the engine coolant temperature faster. It can be turned on or

off, please refer to the ″Duramax Diesel Supplement″ Owner’s Manual for more information.
High Idle

Is available as an option (RPO UF3) on certain HD models with cruise control. This system can be used to increase your engine idle

speed for whatever reason an owner wishes: more generator output at idle, belt driven add on equipment, etc. The cruise control

buttons located on the left hand side of the steering wheel are used to operate the High Idle option. For more information see the

Owner’s Manual or online at ″www.gmupfitter.com″.
PTO (power take-off)

Is available as an option (RPO PTO) only on 3500 Chassis Cab models equipped with the 6.6L Diesel Engine and Allison 6-speed

transmission. The PTO allows the user to create an auxiliary power

source for running add-on equipment, such as salt spreaders, pumps, winches, lift buckets, etc. The dash mounted PTO switch is

used to turn on the PTO and controls engine speed to values higher

than normal base idle. For more information see the ″Duramax Diesel Supplement″ Owner’s Manual or online at

″www.gmupfitter.com″.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved

without completing every step, the remaining steps do not need to be performed.
© 2016 General Motors. All Rights Reserved.

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