When your 2006 Toyota Prius encounters issues during a smog check, especially concerning OBD2 system communication, it’s crucial to understand where the problem might lie. If you’ve already tried multiple smog check stations equipped with BAR-OIS testing equipment, and the problem persists, the focus should shift towards your vehicle itself.
It’s important to note that the 2006 Prius is not listed among vehicles known to have OBD II implementation problems with BAR’s equipment. This suggests that the issue is less likely to be a software glitch and more likely related to hardware, specifically wiring, connectors, or the Engine Control Unit (ECU).
On second-generation Prius models like the 2006 version, the Controller Area Network (CAN) bus, which facilitates communication between the ECM and the hybrid vehicle control ECU, is directly accessible at the DLC3 (OBD II) diagnostic connector. The symptoms you’re experiencing, where issues arise when something is plugged into the DLC3 connector, could be indicative of a fault in the CAN bus lines. These lines might be shorted to ground, battery voltage, or even to each other, especially if the fault is intermittent and triggered by connecting to the DLC3 port.
To effectively diagnose this, the Toyota Prius Repair Manual is an invaluable resource. Within the Engine/Hybrid System section, specifically under “P112 Hybrid Vehicle Control: Hybrid Control System: Diagnosis System,” you’ll find a detailed table outlining voltage and resistance measurements at the DLC3 connector. Using a multimeter, you can carefully check these measurements. Exercise caution to avoid damaging the terminals by forcing the meter probes. While testing, try gently wiggling the DLC3 connector to see if there are any fluctuations in your readings, which could indicate a loose connection.
Furthermore, the Repair Manual provides comprehensive step-by-step procedures for thoroughly inspecting the CAN bus system. Navigate to the Power Source/Network section, and then to “CAN Communication: CAN Communication System.” Pay close attention to topics such as “CAN Bus Line,” “Open in CAN Main Wire,” “Short in CAN Bus Lines,” “Short to B+ in CAN Bus Line,” and “Short to GND in CAN Bus Line.” These sections will guide you through detailed checks to pinpoint any breaks, shorts, or other issues within the CAN bus network.
Remember, assessing the terminals isn’t just about visual inspection. Even if they appear visually fine, they might not be making proper contact with inserted pins. Ideally, a terminal gauge of the correct thickness (0.80 or 0.82 mm, as per SAE J1962 standards) should be used to accurately check the terminal contact. This ensures reliable communication through the diagnostic port and accurate system checks.
