The scan tool has been used but no fault codes come up and it can't find the module
Not all scan tools are created equal. Most only display engine/trans codes. You really need a Tech2 or equivalent. Perhaps one of our Perth members has one and can help you, otherwise it might require a trip to a Holden dealer. Note the last sentence in the description below.
"Also released for VT Series II Models is the new GEN III V8 engine. The Powertrain Control Module (PCM) for this engine uses what is referred to as ‘Class 2’ serial communication. All other control modules, including the BCM, communicate serial data, in what is referred to as UART (Universal Asynchronous Receive and Transmit). The ‘Class 2’ communication is more sophisticated than UART, and as such, requires a Powertrain Interface Module (PIM) to convert Class 2 communication into UART.
In simple terms, the GEN III V8 engine PCM communicates in a different language than the other control modules and therefore requires the PIM to translate the PCM information into the same language as the other control modules communicate in.
Specific software has been developed for use with the TECH 2 diagnostic scan tool to assist with various vehicle electrical system fault finding."