Permanent bus faults

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.

The ICM contains lists of all the control modules on the three busses in the car in question. When you read out DTCs, Tech 2 always starts by contacting the ICM to check which control modules should be present in the vehicle. Tech 2 then checks which control modules in the car are communicating. If a control module is missing, or if an additional control module has been fitted, this is displayed. Nothing is displayed if the numbers of identities agree. If there is a difference, you are given the opportunity to start fault diagnosis or to accept the new control module configuration. You may wish to accept the new configuration if a control module has been fitted or permanently removed. Tech 2 will then update the lists in the ICM so that no warning is displayed in the future. Tech 2 displays if a control module on the bus is missing. This means that if all control modules connected to the buses are communicating correctly, the diagnostic tool does not display a warning. If one of the O-bus systems is missing, the entire O-bus will be down, and in which case there will be a DTC in the ICM. To find out where the break is, disconnect then reconnect the battery cable. All O-bus systems will then be initiated at the same time, allowing the ICM to calculate how many control modules sent a light signal, in other words, how far back along the ring the break is.