Owner's Problem Description
The owner reports intermittent starting issues with a 2000 Saturn SC2. Initially, the vehicle would not start at all, leading the previous owner to seek mechanic help. The current mechanic observed orange spark on the #1 plug, suspecting the ignition control module was faulty. After running fine for three days, the vehicle stalled when cut off while backing out after a quick store visit, and subsequently cranked but did not start until five hours later. The owner is concerned that stalling may have contributed to the problem.
Professional Technical Analysis
The 2000 Saturn SC2, equipped with a 1.9L SOHC engine and a 5-speed manual transmission, has an estimated mileage of around 120,000 miles. The vehicle displays intermittent starting issues, primarily characterized by failure to start after stalling. The initial diagnostics revealed an orange spark at the #1 plug, prompting suspicion of the ignition control module's integrity. However, the absence of trouble codes during OBD-II scanning suggests a more complex issue. The vehicle exhibited successful starts initially but failed to restart after stalling, indicating potential ignition system failure or fuel delivery issues. The crankshaft position sensor is a common failure point in these models, often leading to a lack of spark, while coolant temperature sensor failures can also disrupt engine performance. A thorough examination of the ignition system, including the ICM and crankshaft position sensor resistance (expected around 800 ohms), is warranted. Current conditions indicate that the vehicle may experience safety concerns due to unpredictable starting behavior, emphasizing the need for urgent diagnostics and repair.
Possible Causes
Most common causes (ordered by frequency):
- Ignition Control Module (ICM) failure: The ICM may be experiencing thermal or electrical issues, leading to intermittent spark generation. This is common in Saturn vehicles of this era. As the ICM heats up, it may fail to provide adequate spark, resulting in starting difficulties after stalling. The typical resistance for the ICM should be verified as it may fail under operational conditions. - Observed orange spark at #1 plug, intermittent starting issues, common failure pattern in similar models.
- Crankshaft Position Sensor (CPS) malfunction: A failure in the CPS can lead to a lack of spark during starting attempts. This sensor is critical for the PCM to determine crankshaft position and timing for ignition events. Testing the CPS resistance should reveal values around 800 ohms; faulty sensors typically show open circuit conditions. - No spark during cranking, common diagnostic recommendation for similar symptoms, expected resistance values.
- Fuel System Issues: Insufficient fuel pressure can restrict the engine from starting. Fuel pressure should be maintained at 35-45 PSI. A pressure gauge can be used to verify this, especially if the vehicle fails to start after stalling. - Potential lack of fuel pressure indicated by starting issues, no codes to suggest fuel delivery failure.
Diagnostic Steps
Professional Diagnosis Process
Follow these systematic steps to accurately diagnose the issue. Each step builds on the previous one to ensure accurate diagnosis.
- STEP 1 - OBD-II Diagnostic Scan: Begin with a complete scan using an OBD-II scanner or the GeekOBD APP to identify any stored codes or freeze frame data that could provide insight into the starting issue. Even if no codes are present, analyzing live data may reveal valuable information regarding the fuel and ignition systems.
- STEP 2 - Fuel Pressure Verification: If the vehicle fails to start, check the fuel pressure using a gauge. The pressure should be within the normal range of 35-45 PSI. If it falls below this, inspect the fuel pump and related components for failure.
- STEP 3 - Spark Test: When the vehicle fails to start, check for spark at the ignition coil and plugs. If no spark is detected, investigate the ignition control module and crankshaft position sensor. The CPS should read approximately 800 ohms; a significant deviation from this indicates failure.
- STEP 4 - Component Testing: If both fuel pressure and spark are present, further test the ignition system components, including the ICM and CPS. Use the GeekOBD APP to monitor system parameters during testing to ensure they operate within spec.
