For 1990-2009 cars

### Test Description

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

1. Obtaining rotational speed for the components rotating at tire/wheel is critical to systematically eliminating specific vehicle component groups. These component rotational speeds can be generated by using the J 38792-VS , Vibrate Software or through calculating them manually.

   Note: Be certain to OBSERVE for disturbances that match the customer's description FIRST, and then look at the J 38792-A Electronic Vibration Analyzer (EVA) 2 frequency which corresponds with that disturbance.

2. Proper location of J 38792-A Sensor onto the component which is most excited by the vibration disturbance is critical to obtain an accurate frequency reading.

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

3. 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, then coasting down within the disturbance range.

4. 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 in the Preface section.
1 | Did you review the Diagnostic Starting Point - Vibration Diagnosis? | Go to Step 2 | Go to Diagnostic Starting Point - Vibration Diagnosis and Correction
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 | Perform troubleshooting before continuing the following steps. Have the concerns been eliminated? | Go to Step 4 | Never operate vehicle. Go to Step 2
4 |

1. Obtain the drive axle final drive ratio.
2. If the J 38792-VS , Vibrate Software, is available, obtain the transmission gear ratios.
3. If the J 38792-VS is NOT available, take note of the tire size of each axle, then calculate the tire rotational speed for each size tire used and calculate the driveshaft rotational speed, if equipped. Refer to Component Rotational Speed Calculation.

Did you obtain the drive ratios with the J 38792-VS , or calculate the component rotational speeds, if J 38792-VS 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

Go to Symptoms - Computer/Integrating Systems

6 | Install the J 38792-A Electronic Vibration Analyzer (EVA) 2. Is the J 38792-A operating properly? | Go to Step 7 | Go to Electronic Vibration Analyzer (EVA) Description and Operation
7 | Did the customer's vibration concern occur ONLY while the vehicle is standing still? | Go To Vibration Analysis - Engine | Go to Step 8
8 |

1. Install the J 38792-A Sensor to the component identified by the customer as most respondent to the vibration. Install the J 38792-A Sensor to steering column, if no component was identified. Then you may need to move the sensor to other locations.
2. Select a smooth, level road and slowly accelerate the vehicle to highway driving speed.
3. Observe the vehicle for disturbances that match the customer's description and note the following conditions:

• | The vehicle speed (km/h, mph)

• | Engine RPM (Revolutions per Minute)

• | Transmission Gear Range and specific gear

• | Note the vibration frequency reading, if detected by the J 38792-A .

• | 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 J 38792-A sensor onto that component and repeat steps 2 and 3.

Were you able to duplicate the customer concern?

Go to Step 9

Go to Vibration Diagnostic Aids

9 |

1. Accelerate the vehicle to a speed high above the speed of the disturbance.
2. Shift into NEUTRAL and allow the vehicle to coast down within the disturbance range.

Does the disturbance still occur while coasting down in NEUTRAL?

Go to Step 11

Go to Step 10

10 |

1. Select a smooth, level road and accelerate slowly up to the disturbance speed.
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 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

11 | Does the J 38792-A detect a dominant frequency? | Go to Step 12 | Go to Symptoms - Vibration Diagnosis and Correction
12 |

1. If the J 38792-VS is NOT available, compare the axle final drive ratio, the specific transmission gear ratio, and the engine RPM with the dominant frequency reading recorded.
2. If the J 38792-VS is NOT available, compare the dominant frequency reading recorded with 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 Step 13

13 | Is the vehicle equipped with all-wheel drive? | Go to Vibration Analysis - Hub and/or Axle Input | Go to Symptoms - Vibration Diagnosis and Correction