This section should serve as a guideline for the technician:
Intermittent Problems - Talk to the operator/driver. Be specific!
Develop your own Driver Questionnaire. Refer to section 6.2.1.
Ask the driver to answer the following questions before attempting to repair an intermittent
problem, or a problem with symptoms but no diagnostic codes. Use this and the response
guideline to these questions.
1. How often does the problem occur? Can you and the driver take the vehicle and
demonstrate the problem in a short time?
2. Has the vehicle been to other shops for the same problem? If so, what was done there?
3. Did the radio, dash gages, or lights momentarily turn OFF when the problem occurred?
4. Does the problem occur only at specific operating conditions? If so, at what load? Is it
light, medium, or heavy?
5. Does the problem occur at a specific engine operating temperature? If so, at what engine
6. Does the problem occur only when above or below specific outside temperatures? In
what temperature range?
7. Does the problem occur during other conditions e.g. during or after rain, spray washing,
8. Did the problem occur at a specific vehicle speed? If so, at what vehicle speed?
9. Does the problem occur at specific engine r/min? If so, at what engine r/min?
Questionnaire Response Guideline
The following are typical responses to the Driver Questionnaire:
1. If the problem is repeatable, take the vehicle for a drive with the DDR connected and
note the conditions when the problem occurs. Be prepared to take snapshot data using
the DDR. Ensure you operate the vehicle after correcting the problem and duplicate the
operating conditions before releasing the unit, to verify the problem is corrected.
2. If the vehicle has been to other shops for the same problem, call the other shops and find
out what has been done. Avoid replacing the same components again unless absolutely
sure they are the problem! It is unlikely a component will fail again following a recent
3. If other vehicle devices are affected, this indicates there may be something wrong with
the ignition wiring. Refer to section 91.2 for information on inspecting the ECM battery
All information subject to change without notice.
6SE497 9709 Copyright © 1997 DETROIT DIESEL CORPORATION