When a DTC OFF is performed on a light vehicle using any tool or tuner via OBD2, bench, or Open, this fault has three possible states: one where the check engine light does not illuminate when the system reports a fault, but the associated error code appears when scanned; another where neither the light nor the error code is displayed; and the third, the normal state, where both the indicator light and the error code may be present.
The problem is that when the vehicle experiences a problem due to this fault, such as something related to the catalytic converter, a correct diagnosis cannot be made because the fault is not displayed on the scanner, limiting us to trying to find the problem through mechanical expertise.
Now that I understand how hexadecimal data works within the CanBus network and I connect the CanBus Multiplex Trainer system, I can find the raw data in real time. This allows me to identify which module is providing unchanging data and I can identify the internal freeze frames when the fault occurred. Furthermore, I can identify the calibration ID, which will allow me to see if there has been a change in the stock programming. Therefore, understanding the live hexadecimal data will allow me to identify these types of hidden faults, simply by connecting the vehicle's OBD2 port.
