Experiencing a frustrating issue where your scan tool refuses to communicate with your 2008 Chevy Cobalt LT 2.2L? This lack of communication can prevent you from diagnosing engine problems, reading trouble codes, and performing essential maintenance. Let’s delve into the troubleshooting steps to get your diagnostic system back online.
One of the first and simplest checks, as highlighted in online forums, involves inspecting the fuses. While you’ve confirmed the trunk fuse is in good condition and free from corrosion, it’s crucial not to stop there. A thorough fuse box inspection is paramount. Consult your owner’s manual for the specific fuse related to the Data Link Connector (DLC) or OBD-II port, and any fuses associated with the Powertrain Control Module (PCM) and Body Control Module (BCM). Remember, even in regions with minimal rust, fuses can still fail due to age or electrical surges.
Moving beyond fuses, the next logical step involves verifying the power and ground to the OBD-II port itself. Pin 16 of the DLC should have battery voltage, while pins 4 and 5 should provide a solid ground. Using a multimeter, you can easily test for both power and ground at these pins. A lack of power or ground here will definitely prevent scan tool communication.
If power and ground to the OBD-II port are confirmed, the issue might lie in the communication network itself, potentially involving the BCM or PCM. The original forum post you referenced touches upon BCM pin testing, which can be insightful. Specifically, the discussion around BCM connector C2, pins 62 and 56, provides clues about the ignition switch circuit and its interaction with the BCM.
In your described scenario, you noted voltage readings on BCM pins 62 and 56 that differ from the user “Charlie” in the forum. While Charlie reported no voltage on pin 56, you are getting readings, albeit varying across key positions. This difference suggests that your ignition switch circuit might be functioning to some extent, but still not correctly facilitating scan tool communication.
The resistance test of the ignition switch, as outlined in the forum, is a valuable diagnostic step. However, the note about pin discrepancies (no wires on pins 60, 61, 63, or 64) highlights the importance of verifying pin locations against your specific vehicle’s wiring diagrams. Always refer to the correct wiring schematics for your 2008 Chevy Cobalt LT 2.2L to ensure accurate testing.
Given that basic checks like fuses and OBD-II port power/ground are often the culprits, systematically working through these steps is essential. If these initial checks don’t resolve the issue, further investigation may require a deeper dive into wiring diagrams, potential CAN bus problems, or even the possibility of a faulty BCM or PCM.
When faced with a “no scan tool communication” issue, a methodical approach is key. Begin with the simple checks and progressively move towards more complex diagnostics. If you’ve exhausted these troubleshooting steps and are still facing communication problems, seeking assistance from a qualified automotive technician with experience in Chevy Cobalt electrical systems is advisable. They possess specialized tools and knowledge to diagnose intricate network and module issues effectively.
