SYMPTOM DIAGNOSIS
Symptom checks cannot be used properly unless the problem occurs while the vehicle is being tested. To reduce diagnostic time, ensure that the basic test steps in the BASIC TESTING and TESTS W/CODES articles were performed before diagnosing by symptom. Symptoms available for diagnosis include the following
- Engine Won't Start
- Engine Starts But Stops
- Rough or Unstable Idle
- Poor Response On Acceleration
- Engine Hesitates or Misses
- Poor Fuel Mileage
- Lack of Power
INTERMITTENT PROBLEM DIAGNOSIS
Intermittent fault testing requires reproducing circuit or component failure to identify the problem. These procedures may lead to the computer setting a fault code which may help in diagnosis.
Use a DVOM to pinpoint faults. When monitoring voltage, ensure ignition switch is in ON position or engine is running. Ensure ignition switch is in OFF position or negative battery cable is disconnected when monitoring circuit resistance. Status changes on DVOM during test procedures indicate area of fault.
See also:
• TESTS W/CODES
• SYSTEM/COMPONENT TESTS