C2D Bus Testing

A bus problem will show up in three basic forms when using the DRBII.

Despite the fact that the vehicle passed the automatic bus test a "NO RESPONSE" message may be displayed in place of an expected value on the DRBII. This will occur whenever a bus wire is open or poorly connected at a module. It will also appear if ground or the power supply is missing at certain modules. Finally the "NO RESPONSE" message may appear if the ignition has been turned off and the body computer has timed out. This makes it fairly impossible to use the DRBII to determine where the problem is until the reason for a "NO RESPONSE" message is found and corrected.

Secondly, there are major bus failures such as "SHORT TO GROUND", "SHORT TO BATTERY", "SHORT TO 5 VOLTS", and "BUS + & BUS - SHORTED TOGETHER". Typically any of these major failures could cause anything from an ENGINE NO START to a blank message screen on the EVIC HEAD. The automatic bus test will not complete or allow access to further system tests at this point and the red light on the DRBII will come on.

"NO TERMINATION", "BIAS LEVEL TOO HIGH", "BIAS LEVEL TOO LOW", "NO BUS BIAS", "BUS - OPEN", "BUS + OPEN", "BUS + & BUS - OPEN", and "NOT RECEIVING BUS MESSAGES CORRECTLY" are the bus messages which, while critical and able to prevent the bus from operating properly, will allow the DRBII to present them on the message screen and then drop through into the next level of testing with no red light. The only interference in testing will come when trying to access a module which is directly related to or causing the bus failure to occur, a "NO RESPONSE" message will appear.