Warning: Refer to Road Test Warning in the Preface section.

Did the customer concern indicate that the vibration occurs ONLY while the vehicle is standing still?

Go to Step 5

Go to Step 2

Visually inspect the tyre and wheel assemblies, steering components and suspension components for any possible faults.

Are the tyre and wheel assemblies, steering components and suspension components in good working condition?

Go to Step 4

Go to Step 3

Note: Do NOT operate the vehicle until the faults are corrected.

Correct the faults with the tyre and wheel assemblies, steering components, and/or the suspension components before proceeding.

Did you correct the faults with the tyre and wheel assemblies, steering components, and/or the suspension components?

Go to Step 4

Go to Step 2

4

1. Obtain the drive shaft final drive ratio.
2. If the vibration analyser has suitable software, obtain the transmission gear ratios.
3. If the a vibration analyser is not available, take note of the tyre size on each axle, then calculate the tyre rotational speed for each size tyre used. Refer to Component Rotational Speed Calculation .

Did you obtain the powertrain ratios for use with the vibration analyser, or calculate the component rotational speeds, if a vibration analyser is NOT available?

Go to Step 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

--

Using a vibration analyser is the preferred method for gathering necessary vibration frequency data.

If a vibration analyser 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 analyser available for use?

Go to Step 7

Go to Step 8

Install the vibration analyser.

Is the vibration analyser operating properly?

Go to Step 8

Check the Vibration Analyzer

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 analyser sensor, if available, to the component identified by the customer as most respondent to the vibration. If no component was identified, install the vibration analyser 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 motorway 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 analyser

•	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 analyser 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.

Note: If the vehicle is equipped with an automatic transmission, let the vehicle freewheel to a stop before shifting back into gear.

2. Shift the vehicle into NEUTRAL and allow the vehicle to freewheel down through the disturbance range.

Does the disturbance still occur while freewheeling-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

If the vibration analyser is not available, refer to Symptoms - Vibration Diagnosis and Correction .

Did the vibration analyser detect a dominant frequency?

Go to Step 13

Go to Symptoms - Vibration Diagnosis and Correction

1. If the vibration analyser HAS the features, use the drive shaft 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 analyser 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 tyre/wheel parameters ONLY?

Go to Vibration Analysis - Tyre and Wheel

Go to Symptoms - Vibration Diagnosis and Correction