SYMPTOM DIAGNOSIS
Symptom checks cannot be used properly unless problem occurs while vehicle is being tested. To reduce diagnostic time, make sure all test procedures in BASIC TESTING article and TESTS W/CODES article were performed before diagnosing a symptom. Following symptoms are available for diagnosis.
- Cranks Normally But Will Not Start
- Cranks Normally But Difficult To Start
- Rough Or Unstable Idle
- High Idle After Warm-Up
- Engine Stalls On Deceleration
- Engine Stalls Intermittently
- Engine Hesitates Or Stumbles On Acceleration
- Engine Surges While Cruising
- Lack Of Power
- Engine Runs Rough On Deceleration
- Abnormal Noise Or Knocking
- Fuel Odor
- Excessive Oil Consumption
- Poor Fuel Mileage
INTERMITTENT PROBLEM DIAGNOSIS
Intermittent fault testing requires duplicating circuit or component failure to identify problem. These procedures may lead to computer setting a fault code which may help in diagnosis.
If problem vehicle does not produce fault codes, monitor voltage or resistance values using a DVOM while attempting to reproduce conditions causing intermittent fault. Abnormal status changes on DVOM indicate a fault has been located.
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:
• PIN VOLTAGE CHARTS