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Test Description

WARNING: This page is about a different car, the 2015 Chevrolet Trax and 2015 Buick Encore. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers on the diagnostic table.

NOTE:

Be certain to OBSERVE for disturbances that match the customers description FIRST, then look at the CH-51450-NVH  Oscilloscope Diagnostic Kit (w/NVH) frequency which corresponds with that disturbance.

  1. 10 

    Proper location of the CH-51450-NVH  oscilloscope accelerometer onto the component which is most excited by the vibration disturbance is critical to obtaining an accurate frequency reading.

    This test will duplicate virtually any disturbance which occurs while the vehicle is in motion.

  2. 11 

    Accelerate to a speed high enough above the speed of the disturbance to allow for the time needed to shift into NEUTRAL and for the engine to decrease in RPM to idle speed before coasting down through the disturbance range.

  3. 12 

    This test will either eliminate or confirm the engine as a contributing cause of the customer concern.

Step Action Yes No
1 Did you review the Diagnostic Starting Point - Vibration Diagnosis? Go to Step 2  Go to Diagnostic Starting Point - Vehicle
2 Did the customer concern indicate that the vibration occurs ONLY while the vehicle is standing still? Go to Step 6  Go to Step 3 
3 Visually inspect the tire and wheel assemblies, steering components and suspension components for any possible faults.
Are the tire and wheel assemblies, steering components and suspension components in good working condition?		 Go to Step 5  Go to Step 4 
4
NOTE:

Do NOT operate the vehicle until the faults are corrected.

Correct the faults with the tire and wheel assemblies, steering components, and/or the suspension components before proceeding.Did you correct the faults with the tire and wheel assemblies, steering components, and/or the suspension components?		 Go to Step 5  Go to Step 3 
5 Obtain the drive axle final drive ratio.
Did you obtain the drive axle final drive ratio?		 Go to Step 6  -
6 Install the CH-51450-NVH  Oscilloscope and the EL-47955  MDI.
Is the CH-51450-NVH  Oscilloscope operating properly?		 Go to Step 7  Oscilloscope Diagnostic Kit Description and Operation 
7 Did the customer concern indicate that the vibration occurs ONLY while the vehicle is standing still? Go to Vibration Analysis - Engine  Go to Step 8 
8 Did the customer concern indicate that the vibration occurs ONLY during heavy acceleration at launch? Go to Step 9  Go to Step 10 
9
  1. Install the CH-51450-NVH-TA183  accelerometer to the pinion area of the drive axle. Route the accelerometer cable clear of rotating parts and loosely secure the wire clear of moving parts. If it is not possible to install the CH-51450-NVH-TA183  accelerometer to the drive axle, install the accelerometer to an exposed portion of the floor panel or seat track in the area that the customer noted is most respondent to the vibration.
  2. Select a smooth, level road.
  3. With the vehicle at a stand-still, apply the brake pedal and place the transmission in the lowest forward gear.
    4. NOTE:

    Do not accelerate to the point of causing the drive wheels to squeal, slip, or hop. This would obscure the results of the test.

  4. Release the brake pedal and accelerate aggressively to 32 km/h (20 mph).
  5. Observe the vehicle for disturbances that match the customers description and note the following conditions:
    • The vibration frequency reading, if detected, by the CH-51450-NVH  Oscilloscope
    • The feel and/or sound of the disturbance
  6. If a reading could not be obtained by the CH-51450-NVH  Oscilloscope, move the CH-51450-NVH-TA183  accelerometer to another part that is respondent to the vibration and repeat Steps 3-5.
Were you able to duplicate the customer concern?		 Go to Vibration Analysis - Hub and/or Axle Input  Go to Step 10 
10 
  1. Install the CH-51450-NVH-TA183  accelerometer to the component identified by the customer as most respondent to the vibration. If no component was identified, install the CH-51450-NVH-TA183  accelerometer to the drivers side right seat rail. You may have to move the sensor to other locations later.
  2. Select a smooth, level road and slowly accelerate the vehicle up to highway speed.
  3. Observe the vehicle for disturbances that match the customers description and note the following conditions or take a snapshot using the CH-51450-NVH  software:
    • The vehicle speed
    • The engine RPM
    • The transmission gear range and the specific gear
    • The vibration frequency reading, if detected, by the CH-51450-NVH  Oscilloscope
    • The feel and/or the sound of the disturbance
  4. If the vibration seems to excite a particular component of the vehicle more than the sear rail, move the CH-51450-NVH-TA183  accelerometer onto that component and repeat Steps 2 and 3.
Were you able to duplicate the customer concern?		 Go to Step 11  Go to Vibration Diagnostic Aids 
11 
  1. Accelerate the vehicle to a speed higher than the speed at which the disturbance occurs.
    2. NOTE:

    If the vehicle is equipped with a continuously variable type automatic transmission, let the vehicle coast to a stop before shifting back into gear.

  2. Shift the vehicle into NEUTRAL and allow the vehicle to coast down through the disturbance range.
Does the disturbance still occur while coasting down in NEUTRAL?		 Go to Step 13  Go to Step 12 
12 
  1. Select a smooth, level road and slowly accelerate the vehicle up to the speed at which the disturbance occurs.
  2. Decelerate and safely downshift by one gear range.
  3. Operate the vehicle at the same VEHICLE SPEED at which the disturbance occurs.
Does the same disturbance still occur while going the same vehicle speed in a lower gear range?		 Go to Vibration Analysis - Hub and/or Axle Input  Go to Vibration Analysis - Engine 
13 If the CH-51450-NVH  Oscilloscope is not available, refer to Symptoms - Vibration Diagnosis and Correction .
Did the CH-51450-NVH  Oscilloscope detect a dominant frequency?		 Go to Step 14  Go to Symptoms - Vibration Diagnosis and Correction 
14 Does the frequency data clearly fall within the tire/wheel parameters ONLY? Go to Vibration Analysis - Tire and Wheel  Go to Symptoms - Vibration Diagnosis and Correction 
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