Fault counter

WARNING: This page is about a different car, the 2003 Saab 9-3. However, it is still accessible from the selected car via links, so may be relevant.

To facilitate fault diagnosis, the control modules on the I and P-bus have fault counters. A counter counts up each time bus communication with the control module is broken and the module loses contact with all other control modules. If the counter value of only one control module increases, the problem is local and easy to find. If the values of several control modules increase, wiring diagrams must be used to see how the control modules are interconnected. A total short circuit will cause all the control modules on the bus in question to count up. The counters stops at 255 and can be reset with Tech 2. A counter showing 255 must be reset to be of any use. Intermittent faults can be detected by jiggling the wiring harness. Problems with the power supply or grounding will not be counted by the counter, despite a loss of communication, since the control module itself is then out of order.

NOTE: It is not uncommon and perfectly normal for the value of a counter in a car that has been driven large distances to be 255.