SYMPTOM DIAGNOSIS
Symptom checks cannot be used properly unless problem occurs while vehicle is being tested. To reduce diagnostic time, ensure steps in BASIC TESTING and G - TESTS W/ CODES (if applicable) articles in this section have been performed before attempting to diagnose a symptom. Symptoms available for diagnosis include the following
- No Start - Cold Engine
- Starts But Stalls - Cold Engine
- Hard To Start - Cold Engine
- No Start - Warm Engine
- Erratic Idle - Warm-Up
- Backfiring
- Incorrect Idle Speed
- Off-Idle Hesitation
- Knocking
- Coasting Hesitation
- Engine Misfire - All Conditions
- Insufficient Engine Power
- Poor Fuel Economy
- Excessive Emissions (HC & NOx).
INTERMITTENT PROBLEM DIAGNOSIS
Intermittent fault testing requires duplicating circuit or component failure to identify the problem. These procedures may lead to the computer setting a fault code (on some systems) 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. A status change on DVOM indicates a fault has been located.
Use a DVOM to pinpoint faults. When monitoring voltage, ensure ignition is in ON position, or engine is running. Ensure ignition 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.