Owner's Problem Description
The owner reports that their 2009 Chevy Cobalt LT will not start following a collision on the driver's front side. They have checked all the fuses and confirmed they are good. However, there is no spark and no fuel pressure. The wiring appears intact, but they are unsure if the OBD-II scanner will work since the car won't start.
Professional Technical Analysis
The 2009 Chevy Cobalt LT is equipped with a 2.2L inline-4 engine and automatic transmission, typically experiencing starting issues due to various electrical failures, especially after a collision. In this case, the vehicle shows no spark and no fuel pressure, indicating potential failures in the ignition system or fuel system. Given the symptoms and the accident history, it’s crucial to investigate the vehicle’s electrical connections and components, especially around the ECM (Engine Control Module) and fuse box. A collision can often cause damage to wiring harnesses or connectors, leading to communication failures between the scanner and the ECM, as well as disruption of power supply to critical systems. Additionally, the absence of spark may suggest issues with the ignition control module or crankshaft position sensor, both of which can be affected by impact damage. The fuel system should be checked for power and ground to the fuel pump, as well as verifying fuel pressure at the rail, which should normally be around 40-50 PSI at the ignition ON position. Without spark and fuel pressure, the vehicle will not start, and safety-critical systems should be prioritized in the diagnostic process. Assessing the wiring integrity and confirming the operational status of the ignition and fuel systems are paramount to identifying the root cause of the no-start condition.
Possible Causes
Most common causes (ordered by frequency):
- Ignition System Failure: The ignition control module (ICM) or crankshaft position sensor may have sustained impact damage, leading to a lack of spark. ICM failures can lead to no output when the signal from the crank sensor is absent. Testing the ICM for proper voltage and ground connections (typically 12V+ at the power input) and confirming the signal from the crankshaft position sensor using a multimeter (around 0.5-5V during cranking) is essential. This issue is common in vehicles after frontal collisions. - No spark during cranking, potential fault codes for ICM or crankshaft position sensor, physical inspection of ICM and wiring shows signs of impact.
- Fuel System Inoperability: The fuel pump may not be receiving power due to damaged wiring or blown fuses. The fuel pressure should be around 40-50 PSI, and if the pump is not activating, checking the fuel pump relay and its associated circuits for continuity and power supply is critical. Inspecting for any damaged connectors or grounds related to the fuel system is necessary, especially after the impact. - No fuel pressure at the rail, relay clicking noise absent when ignition is turned on, visual inspection of fuel pump wiring.
- Electrical Connections Failure: Following an accident, electrical connections, especially at the fuse box and ECM, may have become loose or damaged. Inspecting all related connectors for corrosion, bent pins, or loose connections can reveal issues that prevent the vehicle from starting. Ensuring that grounds are intact and measuring voltage at various points will help identify where the electrical fault lies. - Loose or corroded connectors found during inspection, continuity tests revealing issues with ground connections.
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 - Initial OBD-II Scan: Use a professional OBD-II scanner or GeekOBD APP to retrieve any existing fault codes which can provide insight into the issue. Since the vehicle will not start, focus on codes related to the ignition and fuel systems. If the scanner does not communicate, check the condition of the OBD-II port and the wiring leading to the ECM.
- STEP 2 - Check Fuel Pressure: Using a fuel pressure gauge, connect it to the fuel rail to check if the fuel pump is functioning. The expected pressure should be between 40-50 PSI with the ignition in the ON position. If pressure is absent, investigate power to the fuel pump and check for any blown fuses or faulty relays.
- STEP 3 - Test Ignition Components: Inspect and test the ignition control module and crankshaft position sensor for functionality. Measure the voltage and continuity at the ICM connector (should see approximately 12V) and test the crankshaft position sensor output while cranking (should vary between 0.5-5V). Replace any faulty components identified during testing.
- STEP 4 - Inspect Wiring and Connectors: Perform a thorough visual inspection of all wiring and connectors related to the ECM and fuse box. Look for signs of damage, corrosion, or loose connections. Use a multimeter to check continuity and ground integrity across all critical connections, ensuring proper electrical flow.
