Owner's Problem Description
The owner's 1992 Suzuki cannot start, with symptoms starting and running initially but failing to restart after stopping. Over two months, various technicians have suggested issues with the control box, and the ignition indicator lamp does not illuminate. The owner seeks assistance to diagnose and resolve the issue.
Professional Technical Analysis
This analysis pertains to a 1992 Suzuki model experiencing chronic no-start conditions, particularly when the vehicle is stopped after initial operation. The vehicle exhibits a history of intermittent starting, with previous technicians suspecting a fault in the control box, which is a common failure point in older Suzuki models due to age and exposure to environmental factors. As the ignition indicator lamp fails to illuminate, this suggests a possible issue in the electrical system or control module. Given the vehicle's age, approximately 30+ years, it's critical to assess the integrity of the wiring harness, connections, and any corrosion that may affect electrical flow. The vehicle's ignition system has been tested, revealing a strong blue spark, indicating that the spark plugs and ignition coil are functioning correctly. Additionally, fuel delivery has been confirmed to the injectors, further narrowing down the potential causes. The failure of the indicator lamp points towards a possible issue with the body control module (BCM) or the main relay, which requires thorough testing. Monitoring voltage at the ignition switch and checking for continuity in the control circuits should be prioritized to identify any breaks or shorts. Current vehicle condition appears stable mechanically, but electrical issues present significant safety concerns, especially in older models where wiring integrity can lead to unpredictable behavior.
Possible Causes
Most common causes (ordered by frequency):
- Body Control Module (BCM) failure: The BCM handles various electrical signals, including the ignition indicator lamp. A failure in the BCM could prevent the lamp from illuminating, indicating an underlying issue. Testing the BCM functionality and checking for fault codes using an OBD-II scan tool is advisable. Common symptoms include intermittent operation of electrical components, which may not be obvious without thorough testing. - Non-functioning ignition indicator lamp, possible stored fault codes in BCM related to electrical issues.
- Main Relay Malfunction: The main relay provides power to the engine control unit and ignition system. If the relay is faulty, it can lead to a no-start condition. Testing the relay for continuity and proper operation under load is essential. A common failure mode includes internal contact failure, which may not be visible without a load test. - No power to the ignition system when attempting to start, continuity tests on the relay show intermittent connectivity.
- Ignition Switch Failure: The ignition switch may be failing to send the proper voltage to the BCM and ignition system. Conducting a voltage drop test across the ignition switch can reveal poor connections or internal failure. A common symptom includes intermittent power loss to the ignition components. - Intermittent electrical issues, voltage drop readings above acceptable limits when the ignition is engaged.
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 Code Retrieval: Begin by using an OBD-II scanner or the GeekOBD APP to retrieve any stored fault codes from the vehicle's computer systems. Pay attention to any codes related to the BCM or ignition system. This initial step is crucial to understanding any underlying issues that may not be immediately observable.
- STEP 2 - Electrical System Voltage Testing: Conduct voltage tests at the ignition switch to determine if it is supplying adequate voltage to the BCM and ignition system. A proper voltage reading at the switch should be around 12V when the key is turned to the 'on' position. If the voltage is significantly lower, further investigation is required.
- STEP 3 - Relay Testing: Test the main relay for continuity and proper operation under load. Check for signs of internal failure by applying power to the relay and observing if it clicks and maintains connectivity. Consider replacing the relay if it fails to operate correctly.
- STEP 4 - BCM Functionality Check: If no issues are found with the ignition switch or relay, perform a functionality test on the BCM. This may involve checking for input/output signals to various components and ensuring proper communication with the vehicle's ECU. Utilize the GeekOBD APP for advanced diagnostics if necessary.
