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Test Description

WARNING: This page is about a different car, the 2019 Buick Cascada, 2018 Buick Cascada, and 2017 Buick Cascada. 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.

  1. 4 

    Obtaining rotational speed for the components rotating at tire/wheel speed is critical to systematically eliminating specific vehicle component groups. These component rotational speeds can be generated by using an electronic vibration analyzer, or through calculating them manually.

  2. 9 
    NOTE:

    Be certain to OBSERVE for disturbances that match the customer's description FIRST, then look at the vibration analyzer frequency which corresponds with that disturbance.

    Proper location of the vibration analyzer sensor 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.

  3. 10 

    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.

  4. 11 

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

Step Action Yes No
WARNING:

Refer to Road Test Warning .
1 Did the customer concern indicate that the vibration occurs ONLY while the vehicle is standing still? Go to Step 5  Go to Step 2 
2 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 4  Go to Step 3 
3
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 4  Go to Step 2 
4 
  1. Obtain the drive axle final drive ratio.
  2. If the vibration analyzer has suitable software, obtain the transmission gear ratios.
  3. If the a vibration analyzer is not available, take note of the tire size on each axle, then calculate the tire rotational speed for each size tire used. Refer to Component Rotational Speed Calculation .
Did you obtain the powertrain ratios for use with the vibration analyzer, or calculate the component rotational speeds, if a vibration analyzer is NOT available?		 Go to Step 5  -
5
  1. Install a scan tool.
  2. With the scan tool, bring up the Powertrain Control Module data list and select Engine Speed.
Is the scan tool operating properly?		 Go to Step 6  -
6 Using a vibration analyzer is the preferred method for gathering necessary vibration frequency data.
If a vibration analyzer is not available, the necessary vibration frequency data will have to be obtained based on symptoms observed during testing. Review Symptoms - Vibration Diagnosis and Correction  to become familiar with the possible frequency ranges. Review Symptoms - Vibration Diagnosis and Correction, as necessary throughout the remainder of diagnostics.
Is a vibration analyzer available for use?		 Go to Step 7  Go to Step 8 
7 Install the vibration analyzer.
Is the vibration analyzer operating properly?		 Go to Step 8  Check the Vibration Analyzer
8 Did the customer concern indicate that the vibration occurs ONLY while the vehicle is standing still? Go to Vibration Analysis - Engine  Go to Step 9 
9 
  1. Install the vibration analyzer sensor, if available, to the component identified by the customer as most respondent to the vibration. If no component was identified, install the vibration analyzer sensor, if available, to the steering column. 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 customer's description and note the following conditions:
    • The vehicle speed
    • The engine RPM
    • The transmission gear range and the specific gear
    • The vibration frequency reading, if detected by the vibration analyzer
    • The feel and/or sound of the disturbance
  4. If the vibration seems to excite a particular component of the vehicle more than the steering column, then move the vibration analyzer sensor, if available, onto that component and repeat steps 2 and 3.
Were you able to duplicate the customer's concern?		 Go to Step 10  Go to Vibration Diagnostic Aids 
10 
  1. Accelerate the vehicle to a speed higher than the speed at which the disturbance occurs.
    2. NOTE:

    If the vehicle is equipped with an 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 12  Go to Step 11 
11 
  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 
12 If the vibration analyzer is not available, refer to Symptoms - Vibration Diagnosis and Correction .
Did the vibration analyzer detect a dominant frequency?		 Go to Step 13  Go to Symptoms - Vibration Diagnosis and Correction 
13
  1. If the vibration analyzer HAS the features, use the drive axle final drive ratio, the specific transmission gear ratio, and the engine RPM to make a comparison to the dominant frequency reading recorded.
  2. If the vibration analyzer does NOT have the features, compare the dominant frequency reading recorded to the component rotational data which you calculated previously.
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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