Check out this thread:
Fault found : 01203
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2000 Audi A6

 

Yeah I found that info before.
01203 - Electrical Connection between ABS and Instrument Cluster: Open or Short to Ground

Possible Symptoms
•ABS Malfunctions
Possible Causes
•Wiring between ABS and Instrument Cluster defective
•Instrument Cluster defective (rare)
Possible Solutions
•Check Wiring between ABS and Instrument Cluster for Short to Ground/Open Circuit
•Check Instrument Cluster

My continuity tests of wiring plug-to-plug & of plug-to-ground all show no open circuit & no short to ground in the wiring. Since I have 2 repaired ABS modules & have same error with both, makes me think it's less likely to be a bad module. I'd like to have a known working module to temporarily swap in to verify. I hope I'm not in the "rare" bad cluster group, but I don't know how to verify, without buying another "good" cluster to check this.