The service bulletin for ETM issues seems to explain whats going on. https://www.scribd.com/document/704563318/ETM-Troubleshooting

The ETM will remain in a fixed position during communication interruptions, and then the ECM will try to control idle via fuel trim to stay running. It also explains ...

Well I got VIDA working on the car and started digging deeper.

Clearing the codes with VIDA instead of 850-OBD2 app seemed to fare better, instead of a salad of codes and an easily repeatable problem we had... only a handful of codes coming back, and a car that was largely drivable. In about 5 ...

Apologies if there is an existing thread, please direct me. However I can't find any mention of this issue anywhere.

The car: 1999 S70 T5, b5234t3, M56. Drives great, no problems that I'm aware of, no ETM symptoms or vacuum leaks. odo @ 330,000 km

The problem: The car starts, runs, idles ...