PI1402A

Bulletin No.: PI1402A
Date: Apr-2017
Subject:
Information on Clunk/Thump Noise on Acceleration Once After Each Key Cycle
Models:
2010-2017 Buick Enclave
2010-2017 Chevrolet Traverse
2010-2016 GMC Acadia
2017 GMC Acadia Limited
2007-2010 Saturn OUTLOOK
Attention:
This PI also applies to any of the above models that may be N.A. Export to Israel, Middle East or China
vehicles.
This PI has been revised to update the Model Years. Please discard PI1402.
Condition/Concern
Some customers may comment that there is clunk/thump noise on acceleration once after each key cycle that may be mistaken as coming from the suspension
or engine compartment.
This clunk/thump noise may be caused by the second phase power-up self-test of the Antilock Brake System (ABS). This self-test begins when the vehicle is
driven at a speed greater than 15 km/h (9 mph) and the EBCM has not detected any traction control/vehicle stability related concerns. This phase of the powerup self-test may be heard or felt by the driver. The system solenoids and ABS pump motor are commanded ON and OFF to verify the proper operation and the
EBCM verifies the ability to return the system to base braking in the event of a failure. The EBCM isolates all of the wheels by briefly closing the four isolation
valves, and occasionally the driver may detect this by experiencing a momentary hard pedal.
Recommendation/Instructions
In most situations, the ABS self-test noise should be considered normal. If a particular vehicle exhibits a noise that is louder than a comparable vehicle, the
brake lines should be inspected for contact with the underbody of the vehicle or the lines may be contacting one another. If any contact is present, the lines
should be isolated to minimize the noise produced during the ABS self-test event.
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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